[sql] Import reference version of SQLite 3.10.2.

third_party/sqlite/sqlite-src-3100200/src/where.c

 /*
 ** 2001 September 15
 **
 ** The author disclaims copyright to this source code.  In place of
 ** a legal notice, here is a blessing:
 **
 **    May you do good and not evil.
 **    May you find forgiveness for yourself and forgive others.
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
 ** This module contains C code that generates VDBE code used to process
 ** the WHERE clause of SQL statements.  This module is responsible for
 ** generating the code that loops through a table looking for applicable
 ** rows.  Indices are selected and used to speed the search when doing
 ** so is applicable.  Because this module is responsible for selecting
 ** indices, you might also think of this module as the "query optimizer".
 */
 #include "sqliteInt.h"
 #include "whereInt.h"
 
+/* Forward declaration of methods */
+static int whereLoopResize(sqlite3*, WhereLoop*, int);
+
+/* Test variable that can be set to enable WHERE tracing */
+#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
+/***/ int sqlite3WhereTrace = 0;
+#endif
+
+
 /*
 ** Return the estimated number of output rows from a WHERE clause
 */
 u64 sqlite3WhereOutputRowCount(WhereInfo *pWInfo){
   return sqlite3LogEstToInt(pWInfo->nRowOut);
 }
 
 /*
 ** Return one of the WHERE_DISTINCT_xxxxx values to indicate how this
 ** WHERE clause returns outputs for DISTINCT processing.
@@ skipping 21 matching lines @@
 
 /*
 ** Return the VDBE address or label to jump to in order to break
 ** out of a WHERE loop.
 */
 int sqlite3WhereBreakLabel(WhereInfo *pWInfo){
   return pWInfo->iBreak;
 }
 
 /*
-** Return TRUE if an UPDATE or DELETE statement can operate directly on
-** the rowids returned by a WHERE clause.  Return FALSE if doing an
-** UPDATE or DELETE might change subsequent WHERE clause results.
+** Return ONEPASS_OFF (0) if an UPDATE or DELETE statement is unable to
+** operate directly on the rowis returned by a WHERE clause.  Return
+** ONEPASS_SINGLE (1) if the statement can operation directly because only
+** a single row is to be changed.  Return ONEPASS_MULTI (2) if the one-pass
+** optimization can be used on multiple 
 **
 ** If the ONEPASS optimization is used (if this routine returns true)
 ** then also write the indices of open cursors used by ONEPASS
 ** into aiCur[0] and aiCur[1].  iaCur[0] gets the cursor of the data
 ** table and iaCur[1] gets the cursor used by an auxiliary index.
 ** Either value may be -1, indicating that cursor is not used.
 ** Any cursors returned will have been opened for writing.
 **
 ** aiCur[0] and aiCur[1] both get -1 if the where-clause logic is
 ** unable to use the ONEPASS optimization.
 */
 int sqlite3WhereOkOnePass(WhereInfo *pWInfo, int *aiCur){
   memcpy(aiCur, pWInfo->aiCurOnePass, sizeof(int)*2);
-  return pWInfo->okOnePass;
+#ifdef WHERETRACE_ENABLED
+  if( sqlite3WhereTrace && pWInfo->eOnePass!=ONEPASS_OFF ){
+    sqlite3DebugPrintf("%s cursors: %d %d\n",
+         pWInfo->eOnePass==ONEPASS_SINGLE ? "ONEPASS_SINGLE" : "ONEPASS_MULTI",
+         aiCur[0], aiCur[1]);
+  }
+#endif
+  return pWInfo->eOnePass;
 }
 
 /*
 ** Move the content of pSrc into pDest
 */
 static void whereOrMove(WhereOrSet *pDest, WhereOrSet *pSrc){
   pDest->n = pSrc->n;
   memcpy(pDest->a, pSrc->a, pDest->n*sizeof(pDest->a[0]));
 }
 
@@ skipping 31 matching lines @@
     if( p->rRun<=rRun ) return 0;
   }
 whereOrInsert_done:
   p->prereq = prereq;
   p->rRun = rRun;
   if( p->nOut>nOut ) p->nOut = nOut;
   return 1;
 }
 
 /*
-** Initialize a preallocated WhereClause structure.
-*/
-static void whereClauseInit(
-  WhereClause *pWC,        /* The WhereClause to be initialized */
-  WhereInfo *pWInfo        /* The WHERE processing context */
-){
-  pWC->pWInfo = pWInfo;
-  pWC->pOuter = 0;
-  pWC->nTerm = 0;
-  pWC->nSlot = ArraySize(pWC->aStatic);
-  pWC->a = pWC->aStatic;
-}
-
-/* Forward reference */
-static void whereClauseClear(WhereClause*);
-
-/*
-** Deallocate all memory associated with a WhereOrInfo object.
-*/
-static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
-  whereClauseClear(&p->wc);
-  sqlite3DbFree(db, p);
-}
-
-/*
-** Deallocate all memory associated with a WhereAndInfo object.
-*/
-static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
-  whereClauseClear(&p->wc);
-  sqlite3DbFree(db, p);
-}
-
-/*
-** Deallocate a WhereClause structure.  The WhereClause structure
-** itself is not freed.  This routine is the inverse of whereClauseInit().
-*/
-static void whereClauseClear(WhereClause *pWC){
-  int i;
-  WhereTerm *a;
-  sqlite3 *db = pWC->pWInfo->pParse->db;
-  for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
-    if( a->wtFlags & TERM_DYNAMIC ){
-      sqlite3ExprDelete(db, a->pExpr);
-    }
-    if( a->wtFlags & TERM_ORINFO ){
-      whereOrInfoDelete(db, a->u.pOrInfo);
-    }else if( a->wtFlags & TERM_ANDINFO ){
-      whereAndInfoDelete(db, a->u.pAndInfo);
-    }
-  }
-  if( pWC->a!=pWC->aStatic ){
-    sqlite3DbFree(db, pWC->a);
-  }
-}
-
-/*
-** Add a single new WhereTerm entry to the WhereClause object pWC.
-** The new WhereTerm object is constructed from Expr p and with wtFlags.
-** The index in pWC->a[] of the new WhereTerm is returned on success.
-** 0 is returned if the new WhereTerm could not be added due to a memory
-** allocation error.  The memory allocation failure will be recorded in
-** the db->mallocFailed flag so that higher-level functions can detect it.
-**
-** This routine will increase the size of the pWC->a[] array as necessary.
-**
-** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
-** for freeing the expression p is assumed by the WhereClause object pWC.
-** This is true even if this routine fails to allocate a new WhereTerm.
-**
-** WARNING:  This routine might reallocate the space used to store
-** WhereTerms.  All pointers to WhereTerms should be invalidated after
-** calling this routine.  Such pointers may be reinitialized by referencing
-** the pWC->a[] array.
-*/
-static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
-  WhereTerm *pTerm;
-  int idx;
-  testcase( wtFlags & TERM_VIRTUAL );
-  if( pWC->nTerm>=pWC->nSlot ){
-    WhereTerm *pOld = pWC->a;
-    sqlite3 *db = pWC->pWInfo->pParse->db;
-    pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
-    if( pWC->a==0 ){
-      if( wtFlags & TERM_DYNAMIC ){
-        sqlite3ExprDelete(db, p);
-      }
-      pWC->a = pOld;
-      return 0;
-    }
-    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
-    if( pOld!=pWC->aStatic ){
-      sqlite3DbFree(db, pOld);
-    }
-    pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
-  }
-  pTerm = &pWC->a[idx = pWC->nTerm++];
-  if( p && ExprHasProperty(p, EP_Unlikely) ){
-    pTerm->truthProb = sqlite3LogEst(p->iTable) - 99;
-  }else{
-    pTerm->truthProb = 1;
-  }
-  pTerm->pExpr = sqlite3ExprSkipCollate(p);
-  pTerm->wtFlags = wtFlags;
-  pTerm->pWC = pWC;
-  pTerm->iParent = -1;
-  return idx;
-}
-
-/*
-** This routine identifies subexpressions in the WHERE clause where
-** each subexpression is separated by the AND operator or some other
-** operator specified in the op parameter.  The WhereClause structure
-** is filled with pointers to subexpressions.  For example:
-**
-**    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
-**           \________/     \_______________/     \________________/
-**            slot[0]            slot[1]               slot[2]
-**
-** The original WHERE clause in pExpr is unaltered.  All this routine
-** does is make slot[] entries point to substructure within pExpr.
-**
-** In the previous sentence and in the diagram, "slot[]" refers to
-** the WhereClause.a[] array.  The slot[] array grows as needed to contain
-** all terms of the WHERE clause.
-*/
-static void whereSplit(WhereClause *pWC, Expr *pExpr, u8 op){
-  pWC->op = op;
-  if( pExpr==0 ) return;
-  if( pExpr->op!=op ){
-    whereClauseInsert(pWC, pExpr, 0);
-  }else{
-    whereSplit(pWC, pExpr->pLeft, op);
-    whereSplit(pWC, pExpr->pRight, op);
-  }
-}
-
-/*
-** Initialize a WhereMaskSet object
-*/
-#define initMaskSet(P)  (P)->n=0
-
-/*
 ** Return the bitmask for the given cursor number.  Return 0 if
 ** iCursor is not in the set.
 */
-static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
+Bitmask sqlite3WhereGetMask(WhereMaskSet *pMaskSet, int iCursor){
   int i;
   assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
   for(i=0; i<pMaskSet->n; i++){
     if( pMaskSet->ix[i]==iCursor ){
       return MASKBIT(i);
     }
   }
   return 0;
 }
 
 /*
 ** Create a new mask for cursor iCursor.
 **
 ** There is one cursor per table in the FROM clause.  The number of
 ** tables in the FROM clause is limited by a test early in the
 ** sqlite3WhereBegin() routine.  So we know that the pMaskSet->ix[]
 ** array will never overflow.
 */
 static void createMask(WhereMaskSet *pMaskSet, int iCursor){
   assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
   pMaskSet->ix[pMaskSet->n++] = iCursor;
 }
 
 /*
-** These routines walk (recursively) an expression tree and generate
-** a bitmask indicating which tables are used in that expression
-** tree.
-*/
-static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
-static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
-static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
-  Bitmask mask = 0;
-  if( p==0 ) return 0;
-  if( p->op==TK_COLUMN ){
-    mask = getMask(pMaskSet, p->iTable);
-    return mask;
-  }
-  mask = exprTableUsage(pMaskSet, p->pRight);
-  mask |= exprTableUsage(pMaskSet, p->pLeft);
-  if( ExprHasProperty(p, EP_xIsSelect) ){
-    mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
-  }else{
-    mask |= exprListTableUsage(pMaskSet, p->x.pList);
-  }
-  return mask;
-}
-static Bitmask exprListTableUsage(WhereMaskSet *pMaskSet, ExprList *pList){
-  int i;
-  Bitmask mask = 0;
-  if( pList ){
-    for(i=0; i<pList->nExpr; i++){
-      mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
-    }
-  }
-  return mask;
-}
-static Bitmask exprSelectTableUsage(WhereMaskSet *pMaskSet, Select *pS){
-  Bitmask mask = 0;
-  while( pS ){
-    SrcList *pSrc = pS->pSrc;
-    mask |= exprListTableUsage(pMaskSet, pS->pEList);
-    mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
-    mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
-    mask |= exprTableUsage(pMaskSet, pS->pWhere);
-    mask |= exprTableUsage(pMaskSet, pS->pHaving);
-    if( ALWAYS(pSrc!=0) ){
-      int i;
-      for(i=0; i<pSrc->nSrc; i++){
-        mask |= exprSelectTableUsage(pMaskSet, pSrc->a[i].pSelect);
-        mask |= exprTableUsage(pMaskSet, pSrc->a[i].pOn);
-      }
-    }
-    pS = pS->pPrior;
-  }
-  return mask;
-}
-
-/*
-** Return TRUE if the given operator is one of the operators that is
-** allowed for an indexable WHERE clause term.  The allowed operators are
-** "=", "<", ">", "<=", ">=", "IN", and "IS NULL"
-*/
-static int allowedOp(int op){
-  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
-  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
-  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
-  assert( TK_GE==TK_EQ+4 );
-  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
-}
-
-/*
-** Commute a comparison operator.  Expressions of the form "X op Y"
-** are converted into "Y op X".
-**
-** If left/right precedence rules come into play when determining the
-** collating sequence, then COLLATE operators are adjusted to ensure
-** that the collating sequence does not change.  For example:
-** "Y collate NOCASE op X" becomes "X op Y" because any collation sequence on
-** the left hand side of a comparison overrides any collation sequence 
-** attached to the right. For the same reason the EP_Collate flag
-** is not commuted.
-*/
-static void exprCommute(Parse *pParse, Expr *pExpr){
-  u16 expRight = (pExpr->pRight->flags & EP_Collate);
-  u16 expLeft = (pExpr->pLeft->flags & EP_Collate);
-  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
-  if( expRight==expLeft ){
-    /* Either X and Y both have COLLATE operator or neither do */
-    if( expRight ){
-      /* Both X and Y have COLLATE operators.  Make sure X is always
-      ** used by clearing the EP_Collate flag from Y. */
-      pExpr->pRight->flags &= ~EP_Collate;
-    }else if( sqlite3ExprCollSeq(pParse, pExpr->pLeft)!=0 ){
-      /* Neither X nor Y have COLLATE operators, but X has a non-default
-      ** collating sequence.  So add the EP_Collate marker on X to cause
-      ** it to be searched first. */
-      pExpr->pLeft->flags |= EP_Collate;
-    }
-  }
-  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
-  if( pExpr->op>=TK_GT ){
-    assert( TK_LT==TK_GT+2 );
-    assert( TK_GE==TK_LE+2 );
-    assert( TK_GT>TK_EQ );
-    assert( TK_GT<TK_LE );
-    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
-    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
-  }
-}
-
-/*
-** Translate from TK_xx operator to WO_xx bitmask.
-*/
-static u16 operatorMask(int op){
-  u16 c;
-  assert( allowedOp(op) );
-  if( op==TK_IN ){
-    c = WO_IN;
-  }else if( op==TK_ISNULL ){
-    c = WO_ISNULL;
-  }else{
-    assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
-    c = (u16)(WO_EQ<<(op-TK_EQ));
-  }
-  assert( op!=TK_ISNULL || c==WO_ISNULL );
-  assert( op!=TK_IN || c==WO_IN );
-  assert( op!=TK_EQ || c==WO_EQ );
-  assert( op!=TK_LT || c==WO_LT );
-  assert( op!=TK_LE || c==WO_LE );
-  assert( op!=TK_GT || c==WO_GT );
-  assert( op!=TK_GE || c==WO_GE );
-  return c;
-}
-
-/*
 ** Advance to the next WhereTerm that matches according to the criteria
 ** established when the pScan object was initialized by whereScanInit().
 ** Return NULL if there are no more matching WhereTerms.
 */
 static WhereTerm *whereScanNext(WhereScan *pScan){
   int iCur;            /* The cursor on the LHS of the term */
-  int iColumn;         /* The column on the LHS of the term.  -1 for IPK */
+  i16 iColumn;         /* The column on the LHS of the term.  -1 for IPK */
   Expr *pX;            /* An expression being tested */
   WhereClause *pWC;    /* Shorthand for pScan->pWC */
   WhereTerm *pTerm;    /* The term being tested */
   int k = pScan->k;    /* Where to start scanning */
 
   while( pScan->iEquiv<=pScan->nEquiv ){
-    iCur = pScan->aEquiv[pScan->iEquiv-2];
-    iColumn = pScan->aEquiv[pScan->iEquiv-1];
+    iCur = pScan->aiCur[pScan->iEquiv-1];
+    iColumn = pScan->aiColumn[pScan->iEquiv-1];
+    if( iColumn==XN_EXPR && pScan->pIdxExpr==0 ) return 0;
     while( (pWC = pScan->pWC)!=0 ){
       for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
         if( pTerm->leftCursor==iCur
          && pTerm->u.leftColumn==iColumn
-         && (pScan->iEquiv<=2 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
+         && (iColumn!=XN_EXPR
+             || sqlite3ExprCompare(pTerm->pExpr->pLeft,pScan->pIdxExpr,iCur)==0)
+         && (pScan->iEquiv<=1 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
         ){
           if( (pTerm->eOperator & WO_EQUIV)!=0
-           && pScan->nEquiv<ArraySize(pScan->aEquiv)
+           && pScan->nEquiv<ArraySize(pScan->aiCur)
+           && (pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight))->op==TK_COLUMN
           ){
             int j;
-            pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight);
-            assert( pX->op==TK_COLUMN );
-            for(j=0; j<pScan->nEquiv; j+=2){
-              if( pScan->aEquiv[j]==pX->iTable
-               && pScan->aEquiv[j+1]==pX->iColumn ){
+            for(j=0; j<pScan->nEquiv; j++){
+              if( pScan->aiCur[j]==pX->iTable
+               && pScan->aiColumn[j]==pX->iColumn ){
                   break;
               }
             }
             if( j==pScan->nEquiv ){
-              pScan->aEquiv[j] = pX->iTable;
-              pScan->aEquiv[j+1] = pX->iColumn;
-              pScan->nEquiv += 2;
+              pScan->aiCur[j] = pX->iTable;
+              pScan->aiColumn[j] = pX->iColumn;
+              pScan->nEquiv++;
             }
           }
           if( (pTerm->eOperator & pScan->opMask)!=0 ){
             /* Verify the affinity and collating sequence match */
             if( pScan->zCollName && (pTerm->eOperator & WO_ISNULL)==0 ){
               CollSeq *pColl;
               Parse *pParse = pWC->pWInfo->pParse;
               pX = pTerm->pExpr;
               if( !sqlite3IndexAffinityOk(pX, pScan->idxaff) ){
                 continue;
               }
               assert(pX->pLeft);
               pColl = sqlite3BinaryCompareCollSeq(pParse,
                                                   pX->pLeft, pX->pRight);
               if( pColl==0 ) pColl = pParse->db->pDfltColl;
               if( sqlite3StrICmp(pColl->zName, pScan->zCollName) ){
                 continue;
               }
             }
-            if( (pTerm->eOperator & WO_EQ)!=0
+            if( (pTerm->eOperator & (WO_EQ|WO_IS))!=0
              && (pX = pTerm->pExpr->pRight)->op==TK_COLUMN
-             && pX->iTable==pScan->aEquiv[0]
-             && pX->iColumn==pScan->aEquiv[1]
+             && pX->iTable==pScan->aiCur[0]
+             && pX->iColumn==pScan->aiColumn[0]
             ){
+              testcase( pTerm->eOperator & WO_IS );
               continue;
             }
             pScan->k = k+1;
             return pTerm;
           }
         }
       }
       pScan->pWC = pScan->pWC->pOuter;
       k = 0;
     }
     pScan->pWC = pScan->pOrigWC;
     k = 0;
-    pScan->iEquiv += 2;
+    pScan->iEquiv++;
   }
   return 0;
 }
 
 /*
 ** Initialize a WHERE clause scanner object.  Return a pointer to the
 ** first match.  Return NULL if there are no matches.
 **
 ** The scanner will be searching the WHERE clause pWC.  It will look
 ** for terms of the form "X <op> <expr>" where X is column iColumn of table
 ** iCur.  The <op> must be one of the operators described by opMask.
 **
 ** If the search is for X and the WHERE clause contains terms of the
 ** form X=Y then this routine might also return terms of the form
 ** "Y <op> <expr>".  The number of levels of transitivity is limited,
 ** but is enough to handle most commonly occurring SQL statements.
 **
 ** If X is not the INTEGER PRIMARY KEY then X must be compatible with
 ** index pIdx.
 */
 static WhereTerm *whereScanInit(
   WhereScan *pScan,       /* The WhereScan object being initialized */
   WhereClause *pWC,       /* The WHERE clause to be scanned */
   int iCur,               /* Cursor to scan for */
   int iColumn,            /* Column to scan for */
   u32 opMask,             /* Operator(s) to scan for */
   Index *pIdx             /* Must be compatible with this index */
 ){
-  int j;
+  int j = 0;
 
   /* memset(pScan, 0, sizeof(*pScan)); */
   pScan->pOrigWC = pWC;
   pScan->pWC = pWC;
+  pScan->pIdxExpr = 0;
+  if( pIdx ){
+    j = iColumn;
+    iColumn = pIdx->aiColumn[j];
+    if( iColumn==XN_EXPR ) pScan->pIdxExpr = pIdx->aColExpr->a[j].pExpr;
+  }
   if( pIdx && iColumn>=0 ){
     pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
-    for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
-      if( NEVER(j>pIdx->nColumn) ) return 0;
-    }
     pScan->zCollName = pIdx->azColl[j];
   }else{
     pScan->idxaff = 0;
     pScan->zCollName = 0;
   }
   pScan->opMask = opMask;
   pScan->k = 0;
-  pScan->aEquiv[0] = iCur;
-  pScan->aEquiv[1] = iColumn;
-  pScan->nEquiv = 2;
-  pScan->iEquiv = 2;
+  pScan->aiCur[0] = iCur;
+  pScan->aiColumn[0] = iColumn;
+  pScan->nEquiv = 1;
+  pScan->iEquiv = 1;
   return whereScanNext(pScan);
 }
 
 /*
 ** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
 ** where X is a reference to the iColumn of table iCur and <op> is one of
 ** the WO_xx operator codes specified by the op parameter.
 ** Return a pointer to the term.  Return 0 if not found.
 **
+** If pIdx!=0 then search for terms matching the iColumn-th column of pIdx
+** rather than the iColumn-th column of table iCur.
+**
 ** The term returned might by Y=<expr> if there is another constraint in
 ** the WHERE clause that specifies that X=Y.  Any such constraints will be
 ** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
-** aEquiv[] array holds X and all its equivalents, with each SQL variable
-** taking up two slots in aEquiv[].  The first slot is for the cursor number
-** and the second is for the column number.  There are 22 slots in aEquiv[]
-** so that means we can look for X plus up to 10 other equivalent values.
-** Hence a search for X will return <expr> if X=A1 and A1=A2 and A2=A3
-** and ... and A9=A10 and A10=<expr>.
+** aiCur[]/iaColumn[] arrays hold X and all its equivalents. There are 11
+** slots in aiCur[]/aiColumn[] so that means we can look for X plus up to 10
+** other equivalent values.  Hence a search for X will return <expr> if X=A1
+** and A1=A2 and A2=A3 and ... and A9=A10 and A10=<expr>.
 **
 ** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
 ** then try for the one with no dependencies on <expr> - in other words where
 ** <expr> is a constant expression of some kind.  Only return entries of
 ** the form "X <op> Y" where Y is a column in another table if no terms of
 ** the form "X <op> <const-expr>" exist.   If no terms with a constant RHS
 ** exist, try to return a term that does not use WO_EQUIV.
 */
-static WhereTerm *findTerm(
+WhereTerm *sqlite3WhereFindTerm(
   WhereClause *pWC,     /* The WHERE clause to be searched */
   int iCur,             /* Cursor number of LHS */
   int iColumn,          /* Column number of LHS */
   Bitmask notReady,     /* RHS must not overlap with this mask */
   u32 op,               /* Mask of WO_xx values describing operator */
   Index *pIdx           /* Must be compatible with this index, if not NULL */
 ){
   WhereTerm *pResult = 0;
   WhereTerm *p;
   WhereScan scan;
 
   p = whereScanInit(&scan, pWC, iCur, iColumn, op, pIdx);
+  op &= WO_EQ|WO_IS;
   while( p ){
     if( (p->prereqRight & notReady)==0 ){
-      if( p->prereqRight==0 && (p->eOperator&WO_EQ)!=0 ){
+      if( p->prereqRight==0 && (p->eOperator&op)!=0 ){
+        testcase( p->eOperator & WO_IS );
         return p;
       }
       if( pResult==0 ) pResult = p;
     }
     p = whereScanNext(&scan);
   }
   return pResult;
 }
 
-/* Forward reference */
-static void exprAnalyze(SrcList*, WhereClause*, int);
-
-/*
-** Call exprAnalyze on all terms in a WHERE clause.  
-*/
-static void exprAnalyzeAll(
-  SrcList *pTabList,       /* the FROM clause */
-  WhereClause *pWC         /* the WHERE clause to be analyzed */
-){
-  int i;
-  for(i=pWC->nTerm-1; i>=0; i--){
-    exprAnalyze(pTabList, pWC, i);
-  }
-}
-
-#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
-/*
-** Check to see if the given expression is a LIKE or GLOB operator that
-** can be optimized using inequality constraints.  Return TRUE if it is
-** so and false if not.
-**
-** In order for the operator to be optimizible, the RHS must be a string
-** literal that does not begin with a wildcard.  
-*/
-static int isLikeOrGlob(
-  Parse *pParse,    /* Parsing and code generating context */
-  Expr *pExpr,      /* Test this expression */
-  Expr **ppPrefix,  /* Pointer to TK_STRING expression with pattern prefix */
-  int *pisComplete, /* True if the only wildcard is % in the last character */
-  int *pnoCase      /* True if uppercase is equivalent to lowercase */
-){
-  const char *z = 0;         /* String on RHS of LIKE operator */
-  Expr *pRight, *pLeft;      /* Right and left size of LIKE operator */
-  ExprList *pList;           /* List of operands to the LIKE operator */
-  int c;                     /* One character in z[] */
-  int cnt;                   /* Number of non-wildcard prefix characters */
-  char wc[3];                /* Wildcard characters */
-  sqlite3 *db = pParse->db;  /* Database connection */
-  sqlite3_value *pVal = 0;
-  int op;                    /* Opcode of pRight */
-
-  if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
-    return 0;
-  }
-#ifdef SQLITE_EBCDIC
-  if( *pnoCase ) return 0;
-#endif
-  pList = pExpr->x.pList;
-  pLeft = pList->a[1].pExpr;
-  if( pLeft->op!=TK_COLUMN 
-   || sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT 
-   || IsVirtual(pLeft->pTab)
-  ){
-    /* IMP: R-02065-49465 The left-hand side of the LIKE or GLOB operator must
-    ** be the name of an indexed column with TEXT affinity. */
-    return 0;
-  }
-  assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */
-
-  pRight = sqlite3ExprSkipCollate(pList->a[0].pExpr);
-  op = pRight->op;
-  if( op==TK_VARIABLE ){
-    Vdbe *pReprepare = pParse->pReprepare;
-    int iCol = pRight->iColumn;
-    pVal = sqlite3VdbeGetBoundValue(pReprepare, iCol, SQLITE_AFF_NONE);
-    if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
-      z = (char *)sqlite3_value_text(pVal);
-    }
-    sqlite3VdbeSetVarmask(pParse->pVdbe, iCol);
-    assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER );
-  }else if( op==TK_STRING ){
-    z = pRight->u.zToken;
-  }
-  if( z ){
-    cnt = 0;
-    while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
-      cnt++;
-    }
-    if( cnt!=0 && 255!=(u8)z[cnt-1] ){
-      Expr *pPrefix;
-      *pisComplete = c==wc[0] && z[cnt+1]==0;
-      pPrefix = sqlite3Expr(db, TK_STRING, z);
-      if( pPrefix ) pPrefix->u.zToken[cnt] = 0;
-      *ppPrefix = pPrefix;
-      if( op==TK_VARIABLE ){
-        Vdbe *v = pParse->pVdbe;
-        sqlite3VdbeSetVarmask(v, pRight->iColumn);
-        if( *pisComplete && pRight->u.zToken[1] ){
-          /* If the rhs of the LIKE expression is a variable, and the current
-          ** value of the variable means there is no need to invoke the LIKE
-          ** function, then no OP_Variable will be added to the program.
-          ** This causes problems for the sqlite3_bind_parameter_name()
-          ** API. To work around them, add a dummy OP_Variable here.
-          */ 
-          int r1 = sqlite3GetTempReg(pParse);
-          sqlite3ExprCodeTarget(pParse, pRight, r1);
-          sqlite3VdbeChangeP3(v, sqlite3VdbeCurrentAddr(v)-1, 0);
-          sqlite3ReleaseTempReg(pParse, r1);
-        }
-      }
-    }else{
-      z = 0;
-    }
-  }
-
-  sqlite3ValueFree(pVal);
-  return (z!=0);
-}
-#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
-
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-/*
-** Check to see if the given expression is of the form
-**
-**         column MATCH expr
-**
-** If it is then return TRUE.  If not, return FALSE.
-*/
-static int isMatchOfColumn(
-  Expr *pExpr      /* Test this expression */
-){
-  ExprList *pList;
-
-  if( pExpr->op!=TK_FUNCTION ){
-    return 0;
-  }
-  if( sqlite3StrICmp(pExpr->u.zToken,"match")!=0 ){
-    return 0;
-  }
-  pList = pExpr->x.pList;
-  if( pList->nExpr!=2 ){
-    return 0;
-  }
-  if( pList->a[1].pExpr->op != TK_COLUMN ){
-    return 0;
-  }
-  return 1;
-}
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-/*
-** If the pBase expression originated in the ON or USING clause of
-** a join, then transfer the appropriate markings over to derived.
-*/
-static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
-  if( pDerived ){
-    pDerived->flags |= pBase->flags & EP_FromJoin;
-    pDerived->iRightJoinTable = pBase->iRightJoinTable;
-  }
-}
-
-#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
-/*
-** Analyze a term that consists of two or more OR-connected
-** subterms.  So in:
-**
-**     ... WHERE  (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
-**                          ^^^^^^^^^^^^^^^^^^^^
-**
-** This routine analyzes terms such as the middle term in the above example.
-** A WhereOrTerm object is computed and attached to the term under
-** analysis, regardless of the outcome of the analysis.  Hence:
-**
-**     WhereTerm.wtFlags   |=  TERM_ORINFO
-**     WhereTerm.u.pOrInfo  =  a dynamically allocated WhereOrTerm object
-**
-** The term being analyzed must have two or more of OR-connected subterms.
-** A single subterm might be a set of AND-connected sub-subterms.
-** Examples of terms under analysis:
-**
-**     (A)     t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
-**     (B)     x=expr1 OR expr2=x OR x=expr3
-**     (C)     t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
-**     (D)     x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
-**     (E)     (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
-**
-** CASE 1:
-**
-** If all subterms are of the form T.C=expr for some single column of C and
-** a single table T (as shown in example B above) then create a new virtual
-** term that is an equivalent IN expression.  In other words, if the term
-** being analyzed is:
-**
-**      x = expr1  OR  expr2 = x  OR  x = expr3
-**
-** then create a new virtual term like this:
-**
-**      x IN (expr1,expr2,expr3)
-**
-** CASE 2:
-**
-** If all subterms are indexable by a single table T, then set
-**
-**     WhereTerm.eOperator              =  WO_OR
-**     WhereTerm.u.pOrInfo->indexable  |=  the cursor number for table T
-**
-** A subterm is "indexable" if it is of the form
-** "T.C <op> <expr>" where C is any column of table T and 
-** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
-** A subterm is also indexable if it is an AND of two or more
-** subsubterms at least one of which is indexable.  Indexable AND 
-** subterms have their eOperator set to WO_AND and they have
-** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
-**
-** From another point of view, "indexable" means that the subterm could
-** potentially be used with an index if an appropriate index exists.
-** This analysis does not consider whether or not the index exists; that
-** is decided elsewhere.  This analysis only looks at whether subterms
-** appropriate for indexing exist.
-**
-** All examples A through E above satisfy case 2.  But if a term
-** also satisfies case 1 (such as B) we know that the optimizer will
-** always prefer case 1, so in that case we pretend that case 2 is not
-** satisfied.
-**
-** It might be the case that multiple tables are indexable.  For example,
-** (E) above is indexable on tables P, Q, and R.
-**
-** Terms that satisfy case 2 are candidates for lookup by using
-** separate indices to find rowids for each subterm and composing
-** the union of all rowids using a RowSet object.  This is similar
-** to "bitmap indices" in other database engines.
-**
-** OTHERWISE:
-**
-** If neither case 1 nor case 2 apply, then leave the eOperator set to
-** zero.  This term is not useful for search.
-*/
-static void exprAnalyzeOrTerm(
-  SrcList *pSrc,            /* the FROM clause */
-  WhereClause *pWC,         /* the complete WHERE clause */
-  int idxTerm               /* Index of the OR-term to be analyzed */
-){
-  WhereInfo *pWInfo = pWC->pWInfo;        /* WHERE clause processing context */
-  Parse *pParse = pWInfo->pParse;         /* Parser context */
-  sqlite3 *db = pParse->db;               /* Database connection */
-  WhereTerm *pTerm = &pWC->a[idxTerm];    /* The term to be analyzed */
-  Expr *pExpr = pTerm->pExpr;             /* The expression of the term */
-  int i;                                  /* Loop counters */
-  WhereClause *pOrWc;       /* Breakup of pTerm into subterms */
-  WhereTerm *pOrTerm;       /* A Sub-term within the pOrWc */
-  WhereOrInfo *pOrInfo;     /* Additional information associated with pTerm */
-  Bitmask chngToIN;         /* Tables that might satisfy case 1 */
-  Bitmask indexable;        /* Tables that are indexable, satisfying case 2 */
-
-  /*
-  ** Break the OR clause into its separate subterms.  The subterms are
-  ** stored in a WhereClause structure containing within the WhereOrInfo
-  ** object that is attached to the original OR clause term.
-  */
-  assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
-  assert( pExpr->op==TK_OR );
-  pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
-  if( pOrInfo==0 ) return;
-  pTerm->wtFlags |= TERM_ORINFO;
-  pOrWc = &pOrInfo->wc;
-  whereClauseInit(pOrWc, pWInfo);
-  whereSplit(pOrWc, pExpr, TK_OR);
-  exprAnalyzeAll(pSrc, pOrWc);
-  if( db->mallocFailed ) return;
-  assert( pOrWc->nTerm>=2 );
-
-  /*
-  ** Compute the set of tables that might satisfy cases 1 or 2.
-  */
-  indexable = ~(Bitmask)0;
-  chngToIN = ~(Bitmask)0;
-  for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
-    if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
-      WhereAndInfo *pAndInfo;
-      assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
-      chngToIN = 0;
-      pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
-      if( pAndInfo ){
-        WhereClause *pAndWC;
-        WhereTerm *pAndTerm;
-        int j;
-        Bitmask b = 0;
-        pOrTerm->u.pAndInfo = pAndInfo;
-        pOrTerm->wtFlags |= TERM_ANDINFO;
-        pOrTerm->eOperator = WO_AND;
-        pAndWC = &pAndInfo->wc;
-        whereClauseInit(pAndWC, pWC->pWInfo);
-        whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
-        exprAnalyzeAll(pSrc, pAndWC);
-        pAndWC->pOuter = pWC;
-        testcase( db->mallocFailed );
-        if( !db->mallocFailed ){
-          for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
-            assert( pAndTerm->pExpr );
-            if( allowedOp(pAndTerm->pExpr->op) ){
-              b |= getMask(&pWInfo->sMaskSet, pAndTerm->leftCursor);
-            }
-          }
-        }
-        indexable &= b;
-      }
-    }else if( pOrTerm->wtFlags & TERM_COPIED ){
-      /* Skip this term for now.  We revisit it when we process the
-      ** corresponding TERM_VIRTUAL term */
-    }else{
-      Bitmask b;
-      b = getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor);
-      if( pOrTerm->wtFlags & TERM_VIRTUAL ){
-        WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
-        b |= getMask(&pWInfo->sMaskSet, pOther->leftCursor);
-      }
-      indexable &= b;
-      if( (pOrTerm->eOperator & WO_EQ)==0 ){
-        chngToIN = 0;
-      }else{
-        chngToIN &= b;
-      }
-    }
-  }
-
-  /*
-  ** Record the set of tables that satisfy case 2.  The set might be
-  ** empty.
-  */
-  pOrInfo->indexable = indexable;
-  pTerm->eOperator = indexable==0 ? 0 : WO_OR;
-
-  /*
-  ** chngToIN holds a set of tables that *might* satisfy case 1.  But
-  ** we have to do some additional checking to see if case 1 really
-  ** is satisfied.
-  **
-  ** chngToIN will hold either 0, 1, or 2 bits.  The 0-bit case means
-  ** that there is no possibility of transforming the OR clause into an
-  ** IN operator because one or more terms in the OR clause contain
-  ** something other than == on a column in the single table.  The 1-bit
-  ** case means that every term of the OR clause is of the form
-  ** "table.column=expr" for some single table.  The one bit that is set
-  ** will correspond to the common table.  We still need to check to make
-  ** sure the same column is used on all terms.  The 2-bit case is when
-  ** the all terms are of the form "table1.column=table2.column".  It
-  ** might be possible to form an IN operator with either table1.column
-  ** or table2.column as the LHS if either is common to every term of
-  ** the OR clause.
-  **
-  ** Note that terms of the form "table.column1=table.column2" (the
-  ** same table on both sizes of the ==) cannot be optimized.
-  */
-  if( chngToIN ){
-    int okToChngToIN = 0;     /* True if the conversion to IN is valid */
-    int iColumn = -1;         /* Column index on lhs of IN operator */
-    int iCursor = -1;         /* Table cursor common to all terms */
-    int j = 0;                /* Loop counter */
-
-    /* Search for a table and column that appears on one side or the
-    ** other of the == operator in every subterm.  That table and column
-    ** will be recorded in iCursor and iColumn.  There might not be any
-    ** such table and column.  Set okToChngToIN if an appropriate table
-    ** and column is found but leave okToChngToIN false if not found.
-    */
-    for(j=0; j<2 && !okToChngToIN; j++){
-      pOrTerm = pOrWc->a;
-      for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
-        assert( pOrTerm->eOperator & WO_EQ );
-        pOrTerm->wtFlags &= ~TERM_OR_OK;
-        if( pOrTerm->leftCursor==iCursor ){
-          /* This is the 2-bit case and we are on the second iteration and
-          ** current term is from the first iteration.  So skip this term. */
-          assert( j==1 );
-          continue;
-        }
-        if( (chngToIN & getMask(&pWInfo->sMaskSet, pOrTerm->leftCursor))==0 ){
-          /* This term must be of the form t1.a==t2.b where t2 is in the
-          ** chngToIN set but t1 is not.  This term will be either preceded
-          ** or follwed by an inverted copy (t2.b==t1.a).  Skip this term 
-          ** and use its inversion. */
-          testcase( pOrTerm->wtFlags & TERM_COPIED );
-          testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
-          assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
-          continue;
-        }
-        iColumn = pOrTerm->u.leftColumn;
-        iCursor = pOrTerm->leftCursor;
-        break;
-      }
-      if( i<0 ){
-        /* No candidate table+column was found.  This can only occur
-        ** on the second iteration */
-        assert( j==1 );
-        assert( IsPowerOfTwo(chngToIN) );
-        assert( chngToIN==getMask(&pWInfo->sMaskSet, iCursor) );
-        break;
-      }
-      testcase( j==1 );
-
-      /* We have found a candidate table and column.  Check to see if that
-      ** table and column is common to every term in the OR clause */
-      okToChngToIN = 1;
-      for(; i>=0 && okToChngToIN; i--, pOrTerm++){
-        assert( pOrTerm->eOperator & WO_EQ );
-        if( pOrTerm->leftCursor!=iCursor ){
-          pOrTerm->wtFlags &= ~TERM_OR_OK;
-        }else if( pOrTerm->u.leftColumn!=iColumn ){
-          okToChngToIN = 0;
-        }else{
-          int affLeft, affRight;
-          /* If the right-hand side is also a column, then the affinities
-          ** of both right and left sides must be such that no type
-          ** conversions are required on the right.  (Ticket #2249)
-          */
-          affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
-          affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
-          if( affRight!=0 && affRight!=affLeft ){
-            okToChngToIN = 0;
-          }else{
-            pOrTerm->wtFlags |= TERM_OR_OK;
-          }
-        }
-      }
-    }
-
-    /* At this point, okToChngToIN is true if original pTerm satisfies
-    ** case 1.  In that case, construct a new virtual term that is 
-    ** pTerm converted into an IN operator.
-    */
-    if( okToChngToIN ){
-      Expr *pDup;            /* A transient duplicate expression */
-      ExprList *pList = 0;   /* The RHS of the IN operator */
-      Expr *pLeft = 0;       /* The LHS of the IN operator */
-      Expr *pNew;            /* The complete IN operator */
-
-      for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
-        if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
-        assert( pOrTerm->eOperator & WO_EQ );
-        assert( pOrTerm->leftCursor==iCursor );
-        assert( pOrTerm->u.leftColumn==iColumn );
-        pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
-        pList = sqlite3ExprListAppend(pWInfo->pParse, pList, pDup);
-        pLeft = pOrTerm->pExpr->pLeft;
-      }
-      assert( pLeft!=0 );
-      pDup = sqlite3ExprDup(db, pLeft, 0);
-      pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0, 0);
-      if( pNew ){
-        int idxNew;
-        transferJoinMarkings(pNew, pExpr);
-        assert( !ExprHasProperty(pNew, EP_xIsSelect) );
-        pNew->x.pList = pList;
-        idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
-        testcase( idxNew==0 );
-        exprAnalyze(pSrc, pWC, idxNew);
-        pTerm = &pWC->a[idxTerm];
-        pWC->a[idxNew].iParent = idxTerm;
-        pTerm->nChild = 1;
-      }else{
-        sqlite3ExprListDelete(db, pList);
-      }
-      pTerm->eOperator = WO_NOOP;  /* case 1 trumps case 2 */
-    }
-  }
-}
-#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
-
-/*
-** The input to this routine is an WhereTerm structure with only the
-** "pExpr" field filled in.  The job of this routine is to analyze the
-** subexpression and populate all the other fields of the WhereTerm
-** structure.
-**
-** If the expression is of the form "<expr> <op> X" it gets commuted
-** to the standard form of "X <op> <expr>".
-**
-** If the expression is of the form "X <op> Y" where both X and Y are
-** columns, then the original expression is unchanged and a new virtual
-** term of the form "Y <op> X" is added to the WHERE clause and
-** analyzed separately.  The original term is marked with TERM_COPIED
-** and the new term is marked with TERM_DYNAMIC (because it's pExpr
-** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
-** is a commuted copy of a prior term.)  The original term has nChild=1
-** and the copy has idxParent set to the index of the original term.
-*/
-static void exprAnalyze(
-  SrcList *pSrc,            /* the FROM clause */
-  WhereClause *pWC,         /* the WHERE clause */
-  int idxTerm               /* Index of the term to be analyzed */
-){
-  WhereInfo *pWInfo = pWC->pWInfo; /* WHERE clause processing context */
-  WhereTerm *pTerm;                /* The term to be analyzed */
-  WhereMaskSet *pMaskSet;          /* Set of table index masks */
-  Expr *pExpr;                     /* The expression to be analyzed */
-  Bitmask prereqLeft;              /* Prerequesites of the pExpr->pLeft */
-  Bitmask prereqAll;               /* Prerequesites of pExpr */
-  Bitmask extraRight = 0;          /* Extra dependencies on LEFT JOIN */
-  Expr *pStr1 = 0;                 /* RHS of LIKE/GLOB operator */
-  int isComplete = 0;              /* RHS of LIKE/GLOB ends with wildcard */
-  int noCase = 0;                  /* LIKE/GLOB distinguishes case */
-  int op;                          /* Top-level operator.  pExpr->op */
-  Parse *pParse = pWInfo->pParse;  /* Parsing context */
-  sqlite3 *db = pParse->db;        /* Database connection */
-
-  if( db->mallocFailed ){
-    return;
-  }
-  pTerm = &pWC->a[idxTerm];
-  pMaskSet = &pWInfo->sMaskSet;
-  pExpr = pTerm->pExpr;
-  assert( pExpr->op!=TK_AS && pExpr->op!=TK_COLLATE );
-  prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
-  op = pExpr->op;
-  if( op==TK_IN ){
-    assert( pExpr->pRight==0 );
-    if( ExprHasProperty(pExpr, EP_xIsSelect) ){
-      pTerm->prereqRight = exprSelectTableUsage(pMaskSet, pExpr->x.pSelect);
-    }else{
-      pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->x.pList);
-    }
-  }else if( op==TK_ISNULL ){
-    pTerm->prereqRight = 0;
-  }else{
-    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
-  }
-  prereqAll = exprTableUsage(pMaskSet, pExpr);
-  if( ExprHasProperty(pExpr, EP_FromJoin) ){
-    Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
-    prereqAll |= x;
-    extraRight = x-1;  /* ON clause terms may not be used with an index
-                       ** on left table of a LEFT JOIN.  Ticket #3015 */
-  }
-  pTerm->prereqAll = prereqAll;
-  pTerm->leftCursor = -1;
-  pTerm->iParent = -1;
-  pTerm->eOperator = 0;
-  if( allowedOp(op) ){
-    Expr *pLeft = sqlite3ExprSkipCollate(pExpr->pLeft);
-    Expr *pRight = sqlite3ExprSkipCollate(pExpr->pRight);
-    u16 opMask = (pTerm->prereqRight & prereqLeft)==0 ? WO_ALL : WO_EQUIV;
-    if( pLeft->op==TK_COLUMN ){
-      pTerm->leftCursor = pLeft->iTable;
-      pTerm->u.leftColumn = pLeft->iColumn;
-      pTerm->eOperator = operatorMask(op) & opMask;
-    }
-    if( pRight && pRight->op==TK_COLUMN ){
-      WhereTerm *pNew;
-      Expr *pDup;
-      u16 eExtraOp = 0;        /* Extra bits for pNew->eOperator */
-      if( pTerm->leftCursor>=0 ){
-        int idxNew;
-        pDup = sqlite3ExprDup(db, pExpr, 0);
-        if( db->mallocFailed ){
-          sqlite3ExprDelete(db, pDup);
-          return;
-        }
-        idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
-        if( idxNew==0 ) return;
-        pNew = &pWC->a[idxNew];
-        pNew->iParent = idxTerm;
-        pTerm = &pWC->a[idxTerm];
-        pTerm->nChild = 1;
-        pTerm->wtFlags |= TERM_COPIED;
-        if( pExpr->op==TK_EQ
-         && !ExprHasProperty(pExpr, EP_FromJoin)
-         && OptimizationEnabled(db, SQLITE_Transitive)
-        ){
-          pTerm->eOperator |= WO_EQUIV;
-          eExtraOp = WO_EQUIV;
-        }
-      }else{
-        pDup = pExpr;
-        pNew = pTerm;
-      }
-      exprCommute(pParse, pDup);
-      pLeft = sqlite3ExprSkipCollate(pDup->pLeft);
-      pNew->leftCursor = pLeft->iTable;
-      pNew->u.leftColumn = pLeft->iColumn;
-      testcase( (prereqLeft | extraRight) != prereqLeft );
-      pNew->prereqRight = prereqLeft | extraRight;
-      pNew->prereqAll = prereqAll;
-      pNew->eOperator = (operatorMask(pDup->op) + eExtraOp) & opMask;
-    }
-  }
-
-#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
-  /* If a term is the BETWEEN operator, create two new virtual terms
-  ** that define the range that the BETWEEN implements.  For example:
-  **
-  **      a BETWEEN b AND c
-  **
-  ** is converted into:
-  **
-  **      (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
-  **
-  ** The two new terms are added onto the end of the WhereClause object.
-  ** The new terms are "dynamic" and are children of the original BETWEEN
-  ** term.  That means that if the BETWEEN term is coded, the children are
-  ** skipped.  Or, if the children are satisfied by an index, the original
-  ** BETWEEN term is skipped.
-  */
-  else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
-    ExprList *pList = pExpr->x.pList;
-    int i;
-    static const u8 ops[] = {TK_GE, TK_LE};
-    assert( pList!=0 );
-    assert( pList->nExpr==2 );
-    for(i=0; i<2; i++){
-      Expr *pNewExpr;
-      int idxNew;
-      pNewExpr = sqlite3PExpr(pParse, ops[i], 
-                             sqlite3ExprDup(db, pExpr->pLeft, 0),
-                             sqlite3ExprDup(db, pList->a[i].pExpr, 0), 0);
-      transferJoinMarkings(pNewExpr, pExpr);
-      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
-      testcase( idxNew==0 );
-      exprAnalyze(pSrc, pWC, idxNew);
-      pTerm = &pWC->a[idxTerm];
-      pWC->a[idxNew].iParent = idxTerm;
-    }
-    pTerm->nChild = 2;
-  }
-#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
-
-#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
-  /* Analyze a term that is composed of two or more subterms connected by
-  ** an OR operator.
-  */
-  else if( pExpr->op==TK_OR ){
-    assert( pWC->op==TK_AND );
-    exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
-    pTerm = &pWC->a[idxTerm];
-  }
-#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
-
-#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
-  /* Add constraints to reduce the search space on a LIKE or GLOB
-  ** operator.
-  **
-  ** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
-  **
-  **          x>='abc' AND x<'abd' AND x LIKE 'abc%'
-  **
-  ** The last character of the prefix "abc" is incremented to form the
-  ** termination condition "abd".
-  */
-  if( pWC->op==TK_AND 
-   && isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
-  ){
-    Expr *pLeft;       /* LHS of LIKE/GLOB operator */
-    Expr *pStr2;       /* Copy of pStr1 - RHS of LIKE/GLOB operator */
-    Expr *pNewExpr1;
-    Expr *pNewExpr2;
-    int idxNew1;
-    int idxNew2;
-    const char *zCollSeqName;     /* Name of collating sequence */
-
-    pLeft = pExpr->x.pList->a[1].pExpr;
-    pStr2 = sqlite3ExprDup(db, pStr1, 0);
-    if( !db->mallocFailed ){
-      u8 c, *pC;       /* Last character before the first wildcard */
-      pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
-      c = *pC;
-      if( noCase ){
-        /* The point is to increment the last character before the first
-        ** wildcard.  But if we increment '@', that will push it into the
-        ** alphabetic range where case conversions will mess up the 
-        ** inequality.  To avoid this, make sure to also run the full
-        ** LIKE on all candidate expressions by clearing the isComplete flag
-        */
-        if( c=='A'-1 ) isComplete = 0;
-        c = sqlite3UpperToLower[c];
-      }
-      *pC = c + 1;
-    }
-    zCollSeqName = noCase ? "NOCASE" : "BINARY";
-    pNewExpr1 = sqlite3ExprDup(db, pLeft, 0);
-    pNewExpr1 = sqlite3PExpr(pParse, TK_GE, 
-           sqlite3ExprAddCollateString(pParse,pNewExpr1,zCollSeqName),
-           pStr1, 0);
-    transferJoinMarkings(pNewExpr1, pExpr);
-    idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
-    testcase( idxNew1==0 );
-    exprAnalyze(pSrc, pWC, idxNew1);
-    pNewExpr2 = sqlite3ExprDup(db, pLeft, 0);
-    pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
-           sqlite3ExprAddCollateString(pParse,pNewExpr2,zCollSeqName),
-           pStr2, 0);
-    transferJoinMarkings(pNewExpr2, pExpr);
-    idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
-    testcase( idxNew2==0 );
-    exprAnalyze(pSrc, pWC, idxNew2);
-    pTerm = &pWC->a[idxTerm];
-    if( isComplete ){
-      pWC->a[idxNew1].iParent = idxTerm;
-      pWC->a[idxNew2].iParent = idxTerm;
-      pTerm->nChild = 2;
-    }
-  }
-#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-  /* Add a WO_MATCH auxiliary term to the constraint set if the
-  ** current expression is of the form:  column MATCH expr.
-  ** This information is used by the xBestIndex methods of
-  ** virtual tables.  The native query optimizer does not attempt
-  ** to do anything with MATCH functions.
-  */
-  if( isMatchOfColumn(pExpr) ){
-    int idxNew;
-    Expr *pRight, *pLeft;
-    WhereTerm *pNewTerm;
-    Bitmask prereqColumn, prereqExpr;
-
-    pRight = pExpr->x.pList->a[0].pExpr;
-    pLeft = pExpr->x.pList->a[1].pExpr;
-    prereqExpr = exprTableUsage(pMaskSet, pRight);
-    prereqColumn = exprTableUsage(pMaskSet, pLeft);
-    if( (prereqExpr & prereqColumn)==0 ){
-      Expr *pNewExpr;
-      pNewExpr = sqlite3PExpr(pParse, TK_MATCH, 
-                              0, sqlite3ExprDup(db, pRight, 0), 0);
-      idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
-      testcase( idxNew==0 );
-      pNewTerm = &pWC->a[idxNew];
-      pNewTerm->prereqRight = prereqExpr;
-      pNewTerm->leftCursor = pLeft->iTable;
-      pNewTerm->u.leftColumn = pLeft->iColumn;
-      pNewTerm->eOperator = WO_MATCH;
-      pNewTerm->iParent = idxTerm;
-      pTerm = &pWC->a[idxTerm];
-      pTerm->nChild = 1;
-      pTerm->wtFlags |= TERM_COPIED;
-      pNewTerm->prereqAll = pTerm->prereqAll;
-    }
-  }
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
-  /* When sqlite_stat3 histogram data is available an operator of the
-  ** form "x IS NOT NULL" can sometimes be evaluated more efficiently
-  ** as "x>NULL" if x is not an INTEGER PRIMARY KEY.  So construct a
-  ** virtual term of that form.
-  **
-  ** Note that the virtual term must be tagged with TERM_VNULL.  This
-  ** TERM_VNULL tag will suppress the not-null check at the beginning
-  ** of the loop.  Without the TERM_VNULL flag, the not-null check at
-  ** the start of the loop will prevent any results from being returned.
-  */
-  if( pExpr->op==TK_NOTNULL
-   && pExpr->pLeft->op==TK_COLUMN
-   && pExpr->pLeft->iColumn>=0
-   && OptimizationEnabled(db, SQLITE_Stat3)
-  ){
-    Expr *pNewExpr;
-    Expr *pLeft = pExpr->pLeft;
-    int idxNew;
-    WhereTerm *pNewTerm;
-
-    pNewExpr = sqlite3PExpr(pParse, TK_GT,
-                            sqlite3ExprDup(db, pLeft, 0),
-                            sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
-
-    idxNew = whereClauseInsert(pWC, pNewExpr,
-                              TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
-    if( idxNew ){
-      pNewTerm = &pWC->a[idxNew];
-      pNewTerm->prereqRight = 0;
-      pNewTerm->leftCursor = pLeft->iTable;
-      pNewTerm->u.leftColumn = pLeft->iColumn;
-      pNewTerm->eOperator = WO_GT;
-      pNewTerm->iParent = idxTerm;
-      pTerm = &pWC->a[idxTerm];
-      pTerm->nChild = 1;
-      pTerm->wtFlags |= TERM_COPIED;
-      pNewTerm->prereqAll = pTerm->prereqAll;
-    }
-  }
-#endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
-
-  /* Prevent ON clause terms of a LEFT JOIN from being used to drive
-  ** an index for tables to the left of the join.
-  */
-  pTerm->prereqRight |= extraRight;
-}
-
 /*
 ** This function searches pList for an entry that matches the iCol-th column
 ** of index pIdx.
 **
 ** If such an expression is found, its index in pList->a[] is returned. If
 ** no expression is found, -1 is returned.
 */
 static int findIndexCol(
   Parse *pParse,                  /* Parse context */
   ExprList *pList,                /* Expression list to search */
   int iBase,                      /* Cursor for table associated with pIdx */
   Index *pIdx,                    /* Index to match column of */
   int iCol                        /* Column of index to match */
 ){
   int i;
   const char *zColl = pIdx->azColl[iCol];
 
   for(i=0; i<pList->nExpr; i++){
     Expr *p = sqlite3ExprSkipCollate(pList->a[i].pExpr);
     if( p->op==TK_COLUMN
      && p->iColumn==pIdx->aiColumn[iCol]
      && p->iTable==iBase
     ){
       CollSeq *pColl = sqlite3ExprCollSeq(pParse, pList->a[i].pExpr);
-      if( ALWAYS(pColl) && 0==sqlite3StrICmp(pColl->zName, zColl) ){
+      if( pColl && 0==sqlite3StrICmp(pColl->zName, zColl) ){
         return i;
       }
     }
   }
 
   return -1;
 }
 
 /*
+** Return TRUE if the iCol-th column of index pIdx is NOT NULL
+*/
+static int indexColumnNotNull(Index *pIdx, int iCol){
+  int j;
+  assert( pIdx!=0 );
+  assert( iCol>=0 && iCol<pIdx->nColumn );
+  j = pIdx->aiColumn[iCol];
+  if( j>=0 ){
+    return pIdx->pTable->aCol[j].notNull;
+  }else if( j==(-1) ){
+    return 1;
+  }else{
+    assert( j==(-2) );
+    return 0;  /* Assume an indexed expression can always yield a NULL */
+
+  }
+}
+
+/*
 ** Return true if the DISTINCT expression-list passed as the third argument
 ** is redundant.
 **
-** A DISTINCT list is redundant if the database contains some subset of
-** columns that are unique and non-null.
+** A DISTINCT list is redundant if any subset of the columns in the
+** DISTINCT list are collectively unique and individually non-null.
 */
 static int isDistinctRedundant(
   Parse *pParse,            /* Parsing context */
   SrcList *pTabList,        /* The FROM clause */
   WhereClause *pWC,         /* The WHERE clause */
   ExprList *pDistinct       /* The result set that needs to be DISTINCT */
 ){
   Table *pTab;
   Index *pIdx;
   int i;                          
@@ skipping 24 matching lines @@
   **      list, or else the WHERE clause contains a term of the form "col=X",
   **      where X is a constant value. The collation sequences of the
   **      comparison and select-list expressions must match those of the index.
   **
   **   3. All of those index columns for which the WHERE clause does not
   **      contain a "col=X" term are subject to a NOT NULL constraint.
   */
   for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
     if( !IsUniqueIndex(pIdx) ) continue;
     for(i=0; i<pIdx->nKeyCol; i++){
-      i16 iCol = pIdx->aiColumn[i];
-      if( 0==findTerm(pWC, iBase, iCol, ~(Bitmask)0, WO_EQ, pIdx) ){
-        int iIdxCol = findIndexCol(pParse, pDistinct, iBase, pIdx, i);
-        if( iIdxCol<0 || pTab->aCol[iCol].notNull==0 ){
-          break;
-        }
+      if( 0==sqlite3WhereFindTerm(pWC, iBase, i, ~(Bitmask)0, WO_EQ, pIdx) ){
+        if( findIndexCol(pParse, pDistinct, iBase, pIdx, i)<0 ) break;
+        if( indexColumnNotNull(pIdx, i)==0 ) break;
       }
     }
     if( i==pIdx->nKeyCol ){
       /* This index implies that the DISTINCT qualifier is redundant. */
       return 1;
     }
   }
 
   return 0;
 }
 
 
 /*
 ** Estimate the logarithm of the input value to base 2.
 */
 static LogEst estLog(LogEst N){
   return N<=10 ? 0 : sqlite3LogEst(N) - 33;
 }
 
 /*
+** Convert OP_Column opcodes to OP_Copy in previously generated code.
+**
+** This routine runs over generated VDBE code and translates OP_Column
+** opcodes into OP_Copy when the table is being accessed via co-routine 
+** instead of via table lookup.
+**
+** If the bIncrRowid parameter is 0, then any OP_Rowid instructions on
+** cursor iTabCur are transformed into OP_Null. Or, if bIncrRowid is non-zero,
+** then each OP_Rowid is transformed into an instruction to increment the
+** value stored in its output register.
+*/
+static void translateColumnToCopy(
+  Vdbe *v,            /* The VDBE containing code to translate */
+  int iStart,         /* Translate from this opcode to the end */
+  int iTabCur,        /* OP_Column/OP_Rowid references to this table */
+  int iRegister,      /* The first column is in this register */
+  int bIncrRowid      /* If non-zero, transform OP_rowid to OP_AddImm(1) */
+){
+  VdbeOp *pOp = sqlite3VdbeGetOp(v, iStart);
+  int iEnd = sqlite3VdbeCurrentAddr(v);
+  for(; iStart<iEnd; iStart++, pOp++){
+    if( pOp->p1!=iTabCur ) continue;
+    if( pOp->opcode==OP_Column ){
+      pOp->opcode = OP_Copy;
+      pOp->p1 = pOp->p2 + iRegister;
+      pOp->p2 = pOp->p3;
+      pOp->p3 = 0;
+    }else if( pOp->opcode==OP_Rowid ){
+      if( bIncrRowid ){
+        /* Increment the value stored in the P2 operand of the OP_Rowid. */
+        pOp->opcode = OP_AddImm;
+        pOp->p1 = pOp->p2;
+        pOp->p2 = 1;
+      }else{
+        pOp->opcode = OP_Null;
+        pOp->p1 = 0;
+        pOp->p3 = 0;
+      }
+    }
+  }
+}
+
+/*
 ** Two routines for printing the content of an sqlite3_index_info
 ** structure.  Used for testing and debugging only.  If neither
 ** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
 ** are no-ops.
 */
 #if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(WHERETRACE_ENABLED)
 static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
   int i;
   if( !sqlite3WhereTrace ) return;
   for(i=0; i<p->nConstraint; i++){
@@ skipping 37 matching lines @@
 ** could be used with an index to access pSrc, assuming an appropriate
 ** index existed.
 */
 static int termCanDriveIndex(
   WhereTerm *pTerm,              /* WHERE clause term to check */
   struct SrcList_item *pSrc,     /* Table we are trying to access */
   Bitmask notReady               /* Tables in outer loops of the join */
 ){
   char aff;
   if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
-  if( (pTerm->eOperator & WO_EQ)==0 ) return 0;
+  if( (pTerm->eOperator & (WO_EQ|WO_IS))==0 ) return 0;
   if( (pTerm->prereqRight & notReady)!=0 ) return 0;
   if( pTerm->u.leftColumn<0 ) return 0;
   aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
   if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
+  testcase( pTerm->pExpr->op==TK_IS );
   return 1;
 }
 #endif
 
 
 #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
 /*
 ** Generate code to construct the Index object for an automatic index
 ** and to set up the WhereLevel object pLevel so that the code generator
 ** makes use of the automatic index.
@@ skipping 16 matching lines @@
   int regRecord;              /* Register holding an index record */
   int n;                      /* Column counter */
   int i;                      /* Loop counter */
   int mxBitCol;               /* Maximum column in pSrc->colUsed */
   CollSeq *pColl;             /* Collating sequence to on a column */
   WhereLoop *pLoop;           /* The Loop object */
   char *zNotUsed;             /* Extra space on the end of pIdx */
   Bitmask idxCols;            /* Bitmap of columns used for indexing */
   Bitmask extraCols;          /* Bitmap of additional columns */
   u8 sentWarning = 0;         /* True if a warnning has been issued */
+  Expr *pPartial = 0;         /* Partial Index Expression */
+  int iContinue = 0;          /* Jump here to skip excluded rows */
+  struct SrcList_item *pTabItem;  /* FROM clause term being indexed */
+  int addrCounter = 0;        /* Address where integer counter is initialized */
+  int regBase;                /* Array of registers where record is assembled */
 
   /* Generate code to skip over the creation and initialization of the
   ** transient index on 2nd and subsequent iterations of the loop. */
   v = pParse->pVdbe;
   assert( v!=0 );
   addrInit = sqlite3CodeOnce(pParse); VdbeCoverage(v);
 
   /* Count the number of columns that will be added to the index
   ** and used to match WHERE clause constraints */
   nKeyCol = 0;
   pTable = pSrc->pTab;
   pWCEnd = &pWC->a[pWC->nTerm];
   pLoop = pLevel->pWLoop;
   idxCols = 0;
   for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    Expr *pExpr = pTerm->pExpr;
+    assert( !ExprHasProperty(pExpr, EP_FromJoin)    /* prereq always non-zero */
+         || pExpr->iRightJoinTable!=pSrc->iCursor   /*   for the right-hand   */
+         || pLoop->prereq!=0 );                     /*   table of a LEFT JOIN */
+    if( pLoop->prereq==0
+     && (pTerm->wtFlags & TERM_VIRTUAL)==0
+     && !ExprHasProperty(pExpr, EP_FromJoin)
+     && sqlite3ExprIsTableConstant(pExpr, pSrc->iCursor) ){
+      pPartial = sqlite3ExprAnd(pParse->db, pPartial,
+                                sqlite3ExprDup(pParse->db, pExpr, 0));
+    }
     if( termCanDriveIndex(pTerm, pSrc, notReady) ){
       int iCol = pTerm->u.leftColumn;
       Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
       testcase( iCol==BMS );
       testcase( iCol==BMS-1 );
       if( !sentWarning ){
         sqlite3_log(SQLITE_WARNING_AUTOINDEX,
             "automatic index on %s(%s)", pTable->zName,
             pTable->aCol[iCol].zName);
         sentWarning = 1;
       }
       if( (idxCols & cMask)==0 ){
-        if( whereLoopResize(pParse->db, pLoop, nKeyCol+1) ) return;
+        if( whereLoopResize(pParse->db, pLoop, nKeyCol+1) ){
+          goto end_auto_index_create;
+        }
         pLoop->aLTerm[nKeyCol++] = pTerm;
         idxCols |= cMask;
       }
     }
   }
   assert( nKeyCol>0 );
   pLoop->u.btree.nEq = pLoop->nLTerm = nKeyCol;
   pLoop->wsFlags = WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WHERE_INDEXED
                      | WHERE_AUTO_INDEX;
 
   /* Count the number of additional columns needed to create a
   ** covering index.  A "covering index" is an index that contains all
   ** columns that are needed by the query.  With a covering index, the
   ** original table never needs to be accessed.  Automatic indices must
   ** be a covering index because the index will not be updated if the
   ** original table changes and the index and table cannot both be used
   ** if they go out of sync.
   */
   extraCols = pSrc->colUsed & (~idxCols | MASKBIT(BMS-1));
-  mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
+  mxBitCol = MIN(BMS-1,pTable->nCol);
   testcase( pTable->nCol==BMS-1 );
   testcase( pTable->nCol==BMS-2 );
   for(i=0; i<mxBitCol; i++){
     if( extraCols & MASKBIT(i) ) nKeyCol++;
   }
   if( pSrc->colUsed & MASKBIT(BMS-1) ){
     nKeyCol += pTable->nCol - BMS + 1;
   }
-  pLoop->wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY;
 
   /* Construct the Index object to describe this index */
   pIdx = sqlite3AllocateIndexObject(pParse->db, nKeyCol+1, 0, &zNotUsed);
-  if( pIdx==0 ) return;
+  if( pIdx==0 ) goto end_auto_index_create;
   pLoop->u.btree.pIndex = pIdx;
   pIdx->zName = "auto-index";
   pIdx->pTable = pTable;
   n = 0;
   idxCols = 0;
   for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
     if( termCanDriveIndex(pTerm, pSrc, notReady) ){
       int iCol = pTerm->u.leftColumn;
       Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
       testcase( iCol==BMS-1 );
       testcase( iCol==BMS );
       if( (idxCols & cMask)==0 ){
         Expr *pX = pTerm->pExpr;
         idxCols |= cMask;
         pIdx->aiColumn[n] = pTerm->u.leftColumn;
         pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
-        pIdx->azColl[n] = ALWAYS(pColl) ? pColl->zName : "BINARY";
+        pIdx->azColl[n] = pColl ? pColl->zName : sqlite3StrBINARY;
         n++;
       }
     }
   }
   assert( (u32)n==pLoop->u.btree.nEq );
 
   /* Add additional columns needed to make the automatic index into
   ** a covering index */
   for(i=0; i<mxBitCol; i++){
     if( extraCols & MASKBIT(i) ){
       pIdx->aiColumn[n] = i;
-      pIdx->azColl[n] = "BINARY";
+      pIdx->azColl[n] = sqlite3StrBINARY;
       n++;
     }
   }
   if( pSrc->colUsed & MASKBIT(BMS-1) ){
     for(i=BMS-1; i<pTable->nCol; i++){
       pIdx->aiColumn[n] = i;
-      pIdx->azColl[n] = "BINARY";
+      pIdx->azColl[n] = sqlite3StrBINARY;
       n++;
     }
   }
   assert( n==nKeyCol );
-  pIdx->aiColumn[n] = -1;
-  pIdx->azColl[n] = "BINARY";
+  pIdx->aiColumn[n] = XN_ROWID;
+  pIdx->azColl[n] = sqlite3StrBINARY;
 
   /* Create the automatic index */
   assert( pLevel->iIdxCur>=0 );
   pLevel->iIdxCur = pParse->nTab++;
   sqlite3VdbeAddOp2(v, OP_OpenAutoindex, pLevel->iIdxCur, nKeyCol+1);
   sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
   VdbeComment((v, "for %s", pTable->zName));
 
   /* Fill the automatic index with content */
-  addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur); VdbeCoverage(v);
+  sqlite3ExprCachePush(pParse);
+  pTabItem = &pWC->pWInfo->pTabList->a[pLevel->iFrom];
+  if( pTabItem->fg.viaCoroutine ){
+    int regYield = pTabItem->regReturn;
+    addrCounter = sqlite3VdbeAddOp2(v, OP_Integer, 0, 0);
+    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pTabItem->addrFillSub);
+    addrTop =  sqlite3VdbeAddOp1(v, OP_Yield, regYield);
+    VdbeCoverage(v);
+    VdbeComment((v, "next row of \"%s\"", pTabItem->pTab->zName));
+  }else{
+    addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur); VdbeCoverage(v);
+  }
+  if( pPartial ){
+    iContinue = sqlite3VdbeMakeLabel(v);
+    sqlite3ExprIfFalse(pParse, pPartial, iContinue, SQLITE_JUMPIFNULL);
+    pLoop->wsFlags |= WHERE_PARTIALIDX;
+  }
   regRecord = sqlite3GetTempReg(pParse);
-  sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 0, 0, 0, 0);
+  regBase = sqlite3GenerateIndexKey(
+      pParse, pIdx, pLevel->iTabCur, regRecord, 0, 0, 0, 0
+  );
   sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
   sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
-  sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1); VdbeCoverage(v);
+  if( pPartial ) sqlite3VdbeResolveLabel(v, iContinue);
+  if( pTabItem->fg.viaCoroutine ){
+    sqlite3VdbeChangeP2(v, addrCounter, regBase+n);
+    translateColumnToCopy(v, addrTop, pLevel->iTabCur, pTabItem->regResult, 1);
+    sqlite3VdbeGoto(v, addrTop);
+    pTabItem->fg.viaCoroutine = 0;
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1); VdbeCoverage(v);
+  }
   sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
   sqlite3VdbeJumpHere(v, addrTop);
   sqlite3ReleaseTempReg(pParse, regRecord);
+  sqlite3ExprCachePop(pParse);
   
   /* Jump here when skipping the initialization */
   sqlite3VdbeJumpHere(v, addrInit);
+
+end_auto_index_create:
+  sqlite3ExprDelete(pParse->db, pPartial);
 }
 #endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
 /*
 ** Allocate and populate an sqlite3_index_info structure. It is the 
 ** responsibility of the caller to eventually release the structure
 ** by passing the pointer returned by this function to sqlite3_free().
 */
 static sqlite3_index_info *allocateIndexInfo(
   Parse *pParse,
   WhereClause *pWC,
+  Bitmask mUnusable,              /* Ignore terms with these prereqs */
   struct SrcList_item *pSrc,
   ExprList *pOrderBy
 ){
   int i, j;
   int nTerm;
   struct sqlite3_index_constraint *pIdxCons;
   struct sqlite3_index_orderby *pIdxOrderBy;
   struct sqlite3_index_constraint_usage *pUsage;
   WhereTerm *pTerm;
   int nOrderBy;
   sqlite3_index_info *pIdxInfo;
 
   /* Count the number of possible WHERE clause constraints referring
   ** to this virtual table */
   for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
     if( pTerm->leftCursor != pSrc->iCursor ) continue;
+    if( pTerm->prereqRight & mUnusable ) continue;
     assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
     testcase( pTerm->eOperator & WO_IN );
     testcase( pTerm->eOperator & WO_ISNULL );
+    testcase( pTerm->eOperator & WO_IS );
     testcase( pTerm->eOperator & WO_ALL );
-    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV))==0 ) continue;
+    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV|WO_IS))==0 ) continue;
     if( pTerm->wtFlags & TERM_VNULL ) continue;
+    assert( pTerm->u.leftColumn>=(-1) );
     nTerm++;
   }
 
   /* If the ORDER BY clause contains only columns in the current 
   ** virtual table then allocate space for the aOrderBy part of
   ** the sqlite3_index_info structure.
   */
   nOrderBy = 0;
   if( pOrderBy ){
     int n = pOrderBy->nExpr;
@@ skipping 27 matching lines @@
   *(int*)&pIdxInfo->nConstraint = nTerm;
   *(int*)&pIdxInfo->nOrderBy = nOrderBy;
   *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
   *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
   *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
                                                                    pUsage;
 
   for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
     u8 op;
     if( pTerm->leftCursor != pSrc->iCursor ) continue;
+    if( pTerm->prereqRight & mUnusable ) continue;
     assert( IsPowerOfTwo(pTerm->eOperator & ~WO_EQUIV) );
     testcase( pTerm->eOperator & WO_IN );
+    testcase( pTerm->eOperator & WO_IS );
     testcase( pTerm->eOperator & WO_ISNULL );
     testcase( pTerm->eOperator & WO_ALL );
-    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV))==0 ) continue;
+    if( (pTerm->eOperator & ~(WO_ISNULL|WO_EQUIV|WO_IS))==0 ) continue;
     if( pTerm->wtFlags & TERM_VNULL ) continue;
+    assert( pTerm->u.leftColumn>=(-1) );
     pIdxCons[j].iColumn = pTerm->u.leftColumn;
     pIdxCons[j].iTermOffset = i;
     op = (u8)pTerm->eOperator & WO_ALL;
     if( op==WO_IN ) op = WO_EQ;
+    if( op==WO_MATCH ){
+      op = pTerm->eMatchOp;
+    }
     pIdxCons[j].op = op;
     /* The direct assignment in the previous line is possible only because
     ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
     ** following asserts verify this fact. */
     assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
     assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
     assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
     assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
     assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
     assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
@@ skipping 48 matching lines @@
     if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
       sqlite3ErrorMsg(pParse, 
           "table %s: xBestIndex returned an invalid plan", pTab->zName);
     }
   }
 
   return pParse->nErr;
 }
 #endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) */
 
-
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
 /*
 ** Estimate the location of a particular key among all keys in an
 ** index.  Store the results in aStat as follows:
 **
-**    aStat[0]      Est. number of rows less than pVal
-**    aStat[1]      Est. number of rows equal to pVal
+**    aStat[0]      Est. number of rows less than pRec
+**    aStat[1]      Est. number of rows equal to pRec
 **
-** Return SQLITE_OK on success.
+** Return the index of the sample that is the smallest sample that
+** is greater than or equal to pRec. Note that this index is not an index
+** into the aSample[] array - it is an index into a virtual set of samples
+** based on the contents of aSample[] and the number of fields in record 
+** pRec. 
 */
-static void whereKeyStats(
+static int whereKeyStats(
   Parse *pParse,              /* Database connection */
   Index *pIdx,                /* Index to consider domain of */
   UnpackedRecord *pRec,       /* Vector of values to consider */
   int roundUp,                /* Round up if true.  Round down if false */
   tRowcnt *aStat              /* OUT: stats written here */
 ){
   IndexSample *aSample = pIdx->aSample;
   int iCol;                   /* Index of required stats in anEq[] etc. */
+  int i;                      /* Index of first sample >= pRec */
+  int iSample;                /* Smallest sample larger than or equal to pRec */
   int iMin = 0;               /* Smallest sample not yet tested */
-  int i = pIdx->nSample;      /* Smallest sample larger than or equal to pRec */
   int iTest;                  /* Next sample to test */
   int res;                    /* Result of comparison operation */
+  int nField;                 /* Number of fields in pRec */
+  tRowcnt iLower = 0;         /* anLt[] + anEq[] of largest sample pRec is > */
 
 #ifndef SQLITE_DEBUG
   UNUSED_PARAMETER( pParse );
 #endif
   assert( pRec!=0 );
-  iCol = pRec->nField - 1;
   assert( pIdx->nSample>0 );
-  assert( pRec->nField>0 && iCol<pIdx->nSampleCol );
+  assert( pRec->nField>0 && pRec->nField<=pIdx->nSampleCol );
+
+  /* Do a binary search to find the first sample greater than or equal
+  ** to pRec. If pRec contains a single field, the set of samples to search
+  ** is simply the aSample[] array. If the samples in aSample[] contain more
+  ** than one fields, all fields following the first are ignored.
+  **
+  ** If pRec contains N fields, where N is more than one, then as well as the
+  ** samples in aSample[] (truncated to N fields), the search also has to
+  ** consider prefixes of those samples. For example, if the set of samples
+  ** in aSample is:
+  **
+  **     aSample[0] = (a, 5) 
+  **     aSample[1] = (a, 10) 
+  **     aSample[2] = (b, 5) 
+  **     aSample[3] = (c, 100) 
+  **     aSample[4] = (c, 105)
+  **
+  ** Then the search space should ideally be the samples above and the 
+  ** unique prefixes [a], [b] and [c]. But since that is hard to organize, 
+  ** the code actually searches this set:
+  **
+  **     0: (a) 
+  **     1: (a, 5) 
+  **     2: (a, 10) 
+  **     3: (a, 10) 
+  **     4: (b) 
+  **     5: (b, 5) 
+  **     6: (c) 
+  **     7: (c, 100) 
+  **     8: (c, 105)
+  **     9: (c, 105)
+  **
+  ** For each sample in the aSample[] array, N samples are present in the
+  ** effective sample array. In the above, samples 0 and 1 are based on 
+  ** sample aSample[0]. Samples 2 and 3 on aSample[1] etc.
+  **
+  ** Often, sample i of each block of N effective samples has (i+1) fields.
+  ** Except, each sample may be extended to ensure that it is greater than or
+  ** equal to the previous sample in the array. For example, in the above, 
+  ** sample 2 is the first sample of a block of N samples, so at first it 
+  ** appears that it should be 1 field in size. However, that would make it 
+  ** smaller than sample 1, so the binary search would not work. As a result, 
+  ** it is extended to two fields. The duplicates that this creates do not 
+  ** cause any problems.
+  */
+  nField = pRec->nField;
+  iCol = 0;
+  iSample = pIdx->nSample * nField;
   do{
-    iTest = (iMin+i)/2;
-    res = sqlite3VdbeRecordCompare(aSample[iTest].n, aSample[iTest].p, pRec);
+    int iSamp;                    /* Index in aSample[] of test sample */
+    int n;                        /* Number of fields in test sample */
+
+    iTest = (iMin+iSample)/2;
+    iSamp = iTest / nField;
+    if( iSamp>0 ){
+      /* The proposed effective sample is a prefix of sample aSample[iSamp].
+      ** Specifically, the shortest prefix of at least (1 + iTest%nField) 
+      ** fields that is greater than the previous effective sample.  */
+      for(n=(iTest % nField) + 1; n<nField; n++){
+        if( aSample[iSamp-1].anLt[n-1]!=aSample[iSamp].anLt[n-1] ) break;
+      }
+    }else{
+      n = iTest + 1;
+    }
+
+    pRec->nField = n;
+    res = sqlite3VdbeRecordCompare(aSample[iSamp].n, aSample[iSamp].p, pRec);
     if( res<0 ){
+      iLower = aSample[iSamp].anLt[n-1] + aSample[iSamp].anEq[n-1];
       iMin = iTest+1;
+    }else if( res==0 && n<nField ){
+      iLower = aSample[iSamp].anLt[n-1];
+      iMin = iTest+1;
+      res = -1;
     }else{
-      i = iTest;
+      iSample = iTest;
+      iCol = n-1;
     }
-  }while( res && iMin<i );
+  }while( res && iMin<iSample );
+  i = iSample / nField;
 
 #ifdef SQLITE_DEBUG
   /* The following assert statements check that the binary search code
   ** above found the right answer. This block serves no purpose other
   ** than to invoke the asserts.  */
-  if( res==0 ){
-    /* If (res==0) is true, then sample $i must be equal to pRec */
-    assert( i<pIdx->nSample );
-    assert( 0==sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)
-         || pParse->db->mallocFailed );
-  }else{
-    /* Otherwise, pRec must be smaller than sample $i and larger than
-    ** sample ($i-1).  */
-    assert( i==pIdx->nSample 
-         || sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)>0
-         || pParse->db->mallocFailed );
-    assert( i==0
-         || sqlite3VdbeRecordCompare(aSample[i-1].n, aSample[i-1].p, pRec)<0
-         || pParse->db->mallocFailed );
+  if( pParse->db->mallocFailed==0 ){
+    if( res==0 ){
+      /* If (res==0) is true, then pRec must be equal to sample i. */
+      assert( i<pIdx->nSample );
+      assert( iCol==nField-1 );
+      pRec->nField = nField;
+      assert( 0==sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec) 
+           || pParse->db->mallocFailed 
+      );
+    }else{
+      /* Unless i==pIdx->nSample, indicating that pRec is larger than
+      ** all samples in the aSample[] array, pRec must be smaller than the
+      ** (iCol+1) field prefix of sample i.  */
+      assert( i<=pIdx->nSample && i>=0 );
+      pRec->nField = iCol+1;
+      assert( i==pIdx->nSample 
+           || sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)>0
+           || pParse->db->mallocFailed );
+
+      /* if i==0 and iCol==0, then record pRec is smaller than all samples
+      ** in the aSample[] array. Otherwise, if (iCol>0) then pRec must
+      ** be greater than or equal to the (iCol) field prefix of sample i.
+      ** If (i>0), then pRec must also be greater than sample (i-1).  */
+      if( iCol>0 ){
+        pRec->nField = iCol;
+        assert( sqlite3VdbeRecordCompare(aSample[i].n, aSample[i].p, pRec)<=0
+             || pParse->db->mallocFailed );
+      }
+      if( i>0 ){
+        pRec->nField = nField;
+        assert( sqlite3VdbeRecordCompare(aSample[i-1].n, aSample[i-1].p, pRec)<0
+             || pParse->db->mallocFailed );
+      }
+    }
   }
 #endif /* ifdef SQLITE_DEBUG */
 
-  /* At this point, aSample[i] is the first sample that is greater than
-  ** or equal to pVal.  Or if i==pIdx->nSample, then all samples are less
-  ** than pVal.  If aSample[i]==pVal, then res==0.
-  */
   if( res==0 ){
+    /* Record pRec is equal to sample i */
+    assert( iCol==nField-1 );
     aStat[0] = aSample[i].anLt[iCol];
     aStat[1] = aSample[i].anEq[iCol];
   }else{
-    tRowcnt iLower, iUpper, iGap;
-    if( i==0 ){
-      iLower = 0;
-      iUpper = aSample[0].anLt[iCol];
+    /* At this point, the (iCol+1) field prefix of aSample[i] is the first 
+    ** sample that is greater than pRec. Or, if i==pIdx->nSample then pRec
+    ** is larger than all samples in the array. */
+    tRowcnt iUpper, iGap;
+    if( i>=pIdx->nSample ){
+      iUpper = sqlite3LogEstToInt(pIdx->aiRowLogEst[0]);
     }else{
-      i64 nRow0 = sqlite3LogEstToInt(pIdx->aiRowLogEst[0]);
-      iUpper = i>=pIdx->nSample ? nRow0 : aSample[i].anLt[iCol];
-      iLower = aSample[i-1].anEq[iCol] + aSample[i-1].anLt[iCol];
+      iUpper = aSample[i].anLt[iCol];
     }
-    aStat[1] = pIdx->aAvgEq[iCol];
+
     if( iLower>=iUpper ){
       iGap = 0;
     }else{
       iGap = iUpper - iLower;
     }
     if( roundUp ){
       iGap = (iGap*2)/3;
     }else{
       iGap = iGap/3;
     }
     aStat[0] = iLower + iGap;
+    aStat[1] = pIdx->aAvgEq[iCol];
   }
+
+  /* Restore the pRec->nField value before returning.  */
+  pRec->nField = nField;
+  return i;
 }
 #endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
 
 /*
 ** If it is not NULL, pTerm is a term that provides an upper or lower
 ** bound on a range scan. Without considering pTerm, it is estimated 
 ** that the scan will visit nNew rows. This function returns the number
 ** estimated to be visited after taking pTerm into account.
 **
 ** If the user explicitly specified a likelihood() value for this term,
 ** then the return value is the likelihood multiplied by the number of
 ** input rows. Otherwise, this function assumes that an "IS NOT NULL" term
 ** has a likelihood of 0.50, and any other term a likelihood of 0.25.
 */
 static LogEst whereRangeAdjust(WhereTerm *pTerm, LogEst nNew){
   LogEst nRet = nNew;
   if( pTerm ){
     if( pTerm->truthProb<=0 ){
       nRet += pTerm->truthProb;
     }else if( (pTerm->wtFlags & TERM_VNULL)==0 ){
       nRet -= 20;        assert( 20==sqlite3LogEst(4) );
     }
   }
   return nRet;
 }
 
+
+#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
+/*
+** Return the affinity for a single column of an index.
+*/
+static char sqlite3IndexColumnAffinity(sqlite3 *db, Index *pIdx, int iCol){
+  assert( iCol>=0 && iCol<pIdx->nColumn );
+  if( !pIdx->zColAff ){
+    if( sqlite3IndexAffinityStr(db, pIdx)==0 ) return SQLITE_AFF_BLOB;
+  }
+  return pIdx->zColAff[iCol];
+}
+#endif
+
+
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
 /* 
 ** This function is called to estimate the number of rows visited by a
 ** range-scan on a skip-scan index. For example:
 **
 **   CREATE INDEX i1 ON t1(a, b, c);
 **   SELECT * FROM t1 WHERE a=? AND c BETWEEN ? AND ?;
 **
 ** Value pLoop->nOut is currently set to the estimated number of rows 
 ** visited for scanning (a=? AND b=?). This function reduces that estimate 
@@ skipping 29 matching lines @@
   WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
   WhereLoop *pLoop,    /* Update the .nOut value of this loop */
   int *pbDone          /* Set to true if at least one expr. value extracted */
 ){
   Index *p = pLoop->u.btree.pIndex;
   int nEq = pLoop->u.btree.nEq;
   sqlite3 *db = pParse->db;
   int nLower = -1;
   int nUpper = p->nSample+1;
   int rc = SQLITE_OK;
-  int iCol = p->aiColumn[nEq];
-  u8 aff = iCol>=0 ? p->pTable->aCol[iCol].affinity : SQLITE_AFF_INTEGER;
+  u8 aff = sqlite3IndexColumnAffinity(db, p, nEq);
   CollSeq *pColl;
   
   sqlite3_value *p1 = 0;          /* Value extracted from pLower */
   sqlite3_value *p2 = 0;          /* Value extracted from pUpper */
   sqlite3_value *pVal = 0;        /* Value extracted from record */
 
   pColl = sqlite3LocateCollSeq(pParse, p->azColl[nEq]);
   if( pLower ){
     rc = sqlite3Stat4ValueFromExpr(pParse, pLower->pExpr->pRight, aff, &p1);
     nLower = 0;
@@ skipping 53 matching lines @@
 ** example, assuming that index p is on t1(a):
 **
 **   ... FROM t1 WHERE a > ? AND a < ? ...
 **                    |_____|   |_____|
 **                       |         |
 **                     pLower    pUpper
 **
 ** If either of the upper or lower bound is not present, then NULL is passed in
 ** place of the corresponding WhereTerm.
 **
-** The value in (pBuilder->pNew->u.btree.nEq) is the index of the index
+** The value in (pBuilder->pNew->u.btree.nEq) is the number of the index
 ** column subject to the range constraint. Or, equivalently, the number of
 ** equality constraints optimized by the proposed index scan. For example,
 ** assuming index p is on t1(a, b), and the SQL query is:
 **
 **   ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
 **
 ** then nEq is set to 1 (as the range restricted column, b, is the second 
 ** left-most column of the index). Or, if the query is:
 **
 **   ... FROM t1 WHERE a > ? AND a < ? ...
 **
 ** then nEq is set to 0.
 **
 ** When this function is called, *pnOut is set to the sqlite3LogEst() of the
 ** number of rows that the index scan is expected to visit without 
-** considering the range constraints. If nEq is 0, this is the number of 
+** considering the range constraints. If nEq is 0, then *pnOut is the number of 
 ** rows in the index. Assuming no error occurs, *pnOut is adjusted (reduced)
 ** to account for the range constraints pLower and pUpper.
 ** 
 ** In the absence of sqlite_stat4 ANALYZE data, or if such data cannot be
 ** used, a single range inequality reduces the search space by a factor of 4. 
 ** and a pair of constraints (x>? AND x<?) reduces the expected number of
 ** rows visited by a factor of 64.
 */
 static int whereRangeScanEst(
   Parse *pParse,       /* Parsing & code generating context */
   WhereLoopBuilder *pBuilder,
   WhereTerm *pLower,   /* Lower bound on the range. ex: "x>123" Might be NULL */
   WhereTerm *pUpper,   /* Upper bound on the range. ex: "x<455" Might be NULL */
   WhereLoop *pLoop     /* Modify the .nOut and maybe .rRun fields */
 ){
   int rc = SQLITE_OK;
   int nOut = pLoop->nOut;
   LogEst nNew;
 
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
   Index *p = pLoop->u.btree.pIndex;
   int nEq = pLoop->u.btree.nEq;
 
-  if( p->nSample>0
-   && nEq<p->nSampleCol
-   && OptimizationEnabled(pParse->db, SQLITE_Stat3) 
-  ){
+  if( p->nSample>0 && nEq<p->nSampleCol ){
     if( nEq==pBuilder->nRecValid ){
       UnpackedRecord *pRec = pBuilder->pRec;
       tRowcnt a[2];
       u8 aff;
 
       /* Variable iLower will be set to the estimate of the number of rows in 
       ** the index that are less than the lower bound of the range query. The
       ** lower bound being the concatenation of $P and $L, where $P is the
       ** key-prefix formed by the nEq values matched against the nEq left-most
       ** columns of the index, and $L is the value in pLower.
       **
       ** Or, if pLower is NULL or $L cannot be extracted from it (because it
       ** is not a simple variable or literal value), the lower bound of the
       ** range is $P. Due to a quirk in the way whereKeyStats() works, even
       ** if $L is available, whereKeyStats() is called for both ($P) and 
-      ** ($P:$L) and the larger of the two returned values used.
+      ** ($P:$L) and the larger of the two returned values is used.
       **
       ** Similarly, iUpper is to be set to the estimate of the number of rows
       ** less than the upper bound of the range query. Where the upper bound
       ** is either ($P) or ($P:$U). Again, even if $U is available, both values
       ** of iUpper are requested of whereKeyStats() and the smaller used.
+      **
+      ** The number of rows between the two bounds is then just iUpper-iLower.
       */
-      tRowcnt iLower;
-      tRowcnt iUpper;
+      tRowcnt iLower;     /* Rows less than the lower bound */
+      tRowcnt iUpper;     /* Rows less than the upper bound */
+      int iLwrIdx = -2;   /* aSample[] for the lower bound */
+      int iUprIdx = -1;   /* aSample[] for the upper bound */
 
       if( pRec ){
         testcase( pRec->nField!=pBuilder->nRecValid );
         pRec->nField = pBuilder->nRecValid;
       }
-      if( nEq==p->nKeyCol ){
-        aff = SQLITE_AFF_INTEGER;
-      }else{
-        aff = p->pTable->aCol[p->aiColumn[nEq]].affinity;
-      }
+      aff = sqlite3IndexColumnAffinity(pParse->db, p, nEq);
+      assert( nEq!=p->nKeyCol || aff==SQLITE_AFF_INTEGER );
       /* Determine iLower and iUpper using ($P) only. */
       if( nEq==0 ){
         iLower = 0;
-        iUpper = sqlite3LogEstToInt(p->aiRowLogEst[0]);
+        iUpper = p->nRowEst0;
       }else{
         /* Note: this call could be optimized away - since the same values must 
         ** have been requested when testing key $P in whereEqualScanEst().  */
         whereKeyStats(pParse, p, pRec, 0, a);
         iLower = a[0];
         iUpper = a[0] + a[1];
       }
 
       assert( pLower==0 || (pLower->eOperator & (WO_GT|WO_GE))!=0 );
       assert( pUpper==0 || (pUpper->eOperator & (WO_LT|WO_LE))!=0 );
       assert( p->aSortOrder!=0 );
       if( p->aSortOrder[nEq] ){
         /* The roles of pLower and pUpper are swapped for a DESC index */
         SWAP(WhereTerm*, pLower, pUpper);
       }
 
       /* If possible, improve on the iLower estimate using ($P:$L). */
       if( pLower ){
         int bOk;                    /* True if value is extracted from pExpr */
         Expr *pExpr = pLower->pExpr->pRight;
         rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
         if( rc==SQLITE_OK && bOk ){
           tRowcnt iNew;
-          whereKeyStats(pParse, p, pRec, 0, a);
+          iLwrIdx = whereKeyStats(pParse, p, pRec, 0, a);
           iNew = a[0] + ((pLower->eOperator & (WO_GT|WO_LE)) ? a[1] : 0);
           if( iNew>iLower ) iLower = iNew;
           nOut--;
           pLower = 0;
         }
       }
 
       /* If possible, improve on the iUpper estimate using ($P:$U). */
       if( pUpper ){
         int bOk;                    /* True if value is extracted from pExpr */
         Expr *pExpr = pUpper->pExpr->pRight;
         rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq, &bOk);
         if( rc==SQLITE_OK && bOk ){
           tRowcnt iNew;
-          whereKeyStats(pParse, p, pRec, 1, a);
+          iUprIdx = whereKeyStats(pParse, p, pRec, 1, a);
           iNew = a[0] + ((pUpper->eOperator & (WO_GT|WO_LE)) ? a[1] : 0);
           if( iNew<iUpper ) iUpper = iNew;
           nOut--;
           pUpper = 0;
         }
       }
 
       pBuilder->pRec = pRec;
       if( rc==SQLITE_OK ){
         if( iUpper>iLower ){
           nNew = sqlite3LogEst(iUpper - iLower);
+          /* TUNING:  If both iUpper and iLower are derived from the same
+          ** sample, then assume they are 4x more selective.  This brings
+          ** the estimated selectivity more in line with what it would be
+          ** if estimated without the use of STAT3/4 tables. */
+          if( iLwrIdx==iUprIdx ) nNew -= 20;  assert( 20==sqlite3LogEst(4) );
         }else{
           nNew = 10;        assert( 10==sqlite3LogEst(2) );
         }
         if( nNew<nOut ){
           nOut = nNew;
         }
         WHERETRACE(0x10, ("STAT4 range scan: %u..%u  est=%d\n",
                            (u32)iLower, (u32)iUpper, nOut));
       }
     }else{
       int bDone = 0;
       rc = whereRangeSkipScanEst(pParse, pLower, pUpper, pLoop, &bDone);
       if( bDone ) return rc;
     }
   }
 #else
   UNUSED_PARAMETER(pParse);
   UNUSED_PARAMETER(pBuilder);
   assert( pLower || pUpper );
 #endif
   assert( pUpper==0 || (pUpper->wtFlags & TERM_VNULL)==0 );
   nNew = whereRangeAdjust(pLower, nOut);
   nNew = whereRangeAdjust(pUpper, nNew);
 
-  /* TUNING: If there is both an upper and lower limit, assume the range is
+  /* TUNING: If there is both an upper and lower limit and neither limit
+  ** has an application-defined likelihood(), assume the range is
   ** reduced by an additional 75%. This means that, by default, an open-ended
   ** range query (e.g. col > ?) is assumed to match 1/4 of the rows in the
   ** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
   ** match 1/64 of the index. */ 
-  if( pLower && pUpper ) nNew -= 20;
+  if( pLower && pLower->truthProb>0 && pUpper && pUpper->truthProb>0 ){
+    nNew -= 20;
+  }
 
   nOut -= (pLower!=0) + (pUpper!=0);
   if( nNew<10 ) nNew = 10;
   if( nNew<nOut ) nOut = nNew;
 #if defined(WHERETRACE_ENABLED)
   if( pLoop->nOut>nOut ){
     WHERETRACE(0x10,("Range scan lowers nOut from %d to %d\n",
                     pLoop->nOut, nOut));
   }
 #endif
@@ skipping 45 matching lines @@
     return SQLITE_NOTFOUND;
   }
 
   /* This is an optimization only. The call to sqlite3Stat4ProbeSetValue()
   ** below would return the same value.  */
   if( nEq>=p->nColumn ){
     *pnRow = 1;
     return SQLITE_OK;
   }
 
-  aff = p->pTable->aCol[p->aiColumn[nEq-1]].affinity;
+  aff = sqlite3IndexColumnAffinity(pParse->db, p, nEq-1);
   rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq-1, &bOk);
   pBuilder->pRec = pRec;
   if( rc!=SQLITE_OK ) return rc;
   if( bOk==0 ) return SQLITE_NOTFOUND;
   pBuilder->nRecValid = nEq;
 
   whereKeyStats(pParse, p, pRec, 0, a);
   WHERETRACE(0x10,("equality scan regions: %d\n", (int)a[1]));
   *pnRow = a[1];
   
@@ skipping 43 matching lines @@
   if( rc==SQLITE_OK ){
     if( nRowEst > nRow0 ) nRowEst = nRow0;
     *pnRow = nRowEst;
     WHERETRACE(0x10,("IN row estimate: est=%d\n", nRowEst));
   }
   assert( pBuilder->nRecValid==nRecValid );
   return rc;
 }
 #endif /* SQLITE_ENABLE_STAT3_OR_STAT4 */
 
-/*
-** Disable a term in the WHERE clause.  Except, do not disable the term
-** if it controls a LEFT OUTER JOIN and it did not originate in the ON
-** or USING clause of that join.
-**
-** Consider the term t2.z='ok' in the following queries:
-**
-**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
-**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
-**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
-**
-** The t2.z='ok' is disabled in the in (2) because it originates
-** in the ON clause.  The term is disabled in (3) because it is not part
-** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
-**
-** Disabling a term causes that term to not be tested in the inner loop
-** of the join.  Disabling is an optimization.  When terms are satisfied
-** by indices, we disable them to prevent redundant tests in the inner
-** loop.  We would get the correct results if nothing were ever disabled,
-** but joins might run a little slower.  The trick is to disable as much
-** as we can without disabling too much.  If we disabled in (1), we'd get
-** the wrong answer.  See ticket #813.
-*/
-static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
-  if( pTerm
-      && (pTerm->wtFlags & TERM_CODED)==0
-      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
-      && (pLevel->notReady & pTerm->prereqAll)==0
-  ){
-    pTerm->wtFlags |= TERM_CODED;
-    if( pTerm->iParent>=0 ){
-      WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
-      if( (--pOther->nChild)==0 ){
-        disableTerm(pLevel, pOther);
-      }
-    }
-  }
-}
-
-/*
-** Code an OP_Affinity opcode to apply the column affinity string zAff
-** to the n registers starting at base. 
-**
-** As an optimization, SQLITE_AFF_NONE entries (which are no-ops) at the
-** beginning and end of zAff are ignored.  If all entries in zAff are
-** SQLITE_AFF_NONE, then no code gets generated.
-**
-** This routine makes its own copy of zAff so that the caller is free
-** to modify zAff after this routine returns.
-*/
-static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
-  Vdbe *v = pParse->pVdbe;
-  if( zAff==0 ){
-    assert( pParse->db->mallocFailed );
-    return;
-  }
-  assert( v!=0 );
-
-  /* Adjust base and n to skip over SQLITE_AFF_NONE entries at the beginning
-  ** and end of the affinity string.
-  */
-  while( n>0 && zAff[0]==SQLITE_AFF_NONE ){
-    n--;
-    base++;
-    zAff++;
-  }
-  while( n>1 && zAff[n-1]==SQLITE_AFF_NONE ){
-    n--;
-  }
-
-  /* Code the OP_Affinity opcode if there is anything left to do. */
-  if( n>0 ){
-    sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
-    sqlite3VdbeChangeP4(v, -1, zAff, n);
-    sqlite3ExprCacheAffinityChange(pParse, base, n);
-  }
-}
-
-
-/*
-** Generate code for a single equality term of the WHERE clause.  An equality
-** term can be either X=expr or X IN (...).   pTerm is the term to be 
-** coded.
-**
-** The current value for the constraint is left in register iReg.
-**
-** For a constraint of the form X=expr, the expression is evaluated and its
-** result is left on the stack.  For constraints of the form X IN (...)
-** this routine sets up a loop that will iterate over all values of X.
-*/
-static int codeEqualityTerm(
-  Parse *pParse,      /* The parsing context */
-  WhereTerm *pTerm,   /* The term of the WHERE clause to be coded */
-  WhereLevel *pLevel, /* The level of the FROM clause we are working on */
-  int iEq,            /* Index of the equality term within this level */
-  int bRev,           /* True for reverse-order IN operations */
-  int iTarget         /* Attempt to leave results in this register */
-){
-  Expr *pX = pTerm->pExpr;
-  Vdbe *v = pParse->pVdbe;
-  int iReg;                  /* Register holding results */
-
-  assert( iTarget>0 );
-  if( pX->op==TK_EQ ){
-    iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
-  }else if( pX->op==TK_ISNULL ){
-    iReg = iTarget;
-    sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
-#ifndef SQLITE_OMIT_SUBQUERY
-  }else{
-    int eType;
-    int iTab;
-    struct InLoop *pIn;
-    WhereLoop *pLoop = pLevel->pWLoop;
-
-    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0
-      && pLoop->u.btree.pIndex!=0
-      && pLoop->u.btree.pIndex->aSortOrder[iEq]
-    ){
-      testcase( iEq==0 );
-      testcase( bRev );
-      bRev = !bRev;
-    }
-    assert( pX->op==TK_IN );
-    iReg = iTarget;
-    eType = sqlite3FindInIndex(pParse, pX, IN_INDEX_LOOP, 0);
-    if( eType==IN_INDEX_INDEX_DESC ){
-      testcase( bRev );
-      bRev = !bRev;
-    }
-    iTab = pX->iTable;
-    sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iTab, 0);
-    VdbeCoverageIf(v, bRev);
-    VdbeCoverageIf(v, !bRev);
-    assert( (pLoop->wsFlags & WHERE_MULTI_OR)==0 );
-    pLoop->wsFlags |= WHERE_IN_ABLE;
-    if( pLevel->u.in.nIn==0 ){
-      pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
-    }
-    pLevel->u.in.nIn++;
-    pLevel->u.in.aInLoop =
-       sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
-                              sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
-    pIn = pLevel->u.in.aInLoop;
-    if( pIn ){
-      pIn += pLevel->u.in.nIn - 1;
-      pIn->iCur = iTab;
-      if( eType==IN_INDEX_ROWID ){
-        pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
-      }else{
-        pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
-      }
-      pIn->eEndLoopOp = bRev ? OP_PrevIfOpen : OP_NextIfOpen;
-      sqlite3VdbeAddOp1(v, OP_IsNull, iReg); VdbeCoverage(v);
-    }else{
-      pLevel->u.in.nIn = 0;
-    }
-#endif
-  }
-  disableTerm(pLevel, pTerm);
-  return iReg;
-}
-
-/*
-** Generate code that will evaluate all == and IN constraints for an
-** index scan.
-**
-** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
-** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
-** The index has as many as three equality constraints, but in this
-** example, the third "c" value is an inequality.  So only two 
-** constraints are coded.  This routine will generate code to evaluate
-** a==5 and b IN (1,2,3).  The current values for a and b will be stored
-** in consecutive registers and the index of the first register is returned.
-**
-** In the example above nEq==2.  But this subroutine works for any value
-** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
-** The only thing it does is allocate the pLevel->iMem memory cell and
-** compute the affinity string.
-**
-** The nExtraReg parameter is 0 or 1.  It is 0 if all WHERE clause constraints
-** are == or IN and are covered by the nEq.  nExtraReg is 1 if there is
-** an inequality constraint (such as the "c>=5 AND c<10" in the example) that
-** occurs after the nEq quality constraints.
-**
-** This routine allocates a range of nEq+nExtraReg memory cells and returns
-** the index of the first memory cell in that range. The code that
-** calls this routine will use that memory range to store keys for
-** start and termination conditions of the loop.
-** key value of the loop.  If one or more IN operators appear, then
-** this routine allocates an additional nEq memory cells for internal
-** use.
-**
-** Before returning, *pzAff is set to point to a buffer containing a
-** copy of the column affinity string of the index allocated using
-** sqlite3DbMalloc(). Except, entries in the copy of the string associated
-** with equality constraints that use NONE affinity are set to
-** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
-**
-**   CREATE TABLE t1(a TEXT PRIMARY KEY, b);
-**   SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
-**
-** In the example above, the index on t1(a) has TEXT affinity. But since
-** the right hand side of the equality constraint (t2.b) has NONE affinity,
-** no conversion should be attempted before using a t2.b value as part of
-** a key to search the index. Hence the first byte in the returned affinity
-** string in this example would be set to SQLITE_AFF_NONE.
-*/
-static int codeAllEqualityTerms(
-  Parse *pParse,        /* Parsing context */
-  WhereLevel *pLevel,   /* Which nested loop of the FROM we are coding */
-  int bRev,             /* Reverse the order of IN operators */
-  int nExtraReg,        /* Number of extra registers to allocate */
-  char **pzAff          /* OUT: Set to point to affinity string */
-){
-  u16 nEq;                      /* The number of == or IN constraints to code */
-  u16 nSkip;                    /* Number of left-most columns to skip */
-  Vdbe *v = pParse->pVdbe;      /* The vm under construction */
-  Index *pIdx;                  /* The index being used for this loop */
-  WhereTerm *pTerm;             /* A single constraint term */
-  WhereLoop *pLoop;             /* The WhereLoop object */
-  int j;                        /* Loop counter */
-  int regBase;                  /* Base register */
-  int nReg;                     /* Number of registers to allocate */
-  char *zAff;                   /* Affinity string to return */
-
-  /* This module is only called on query plans that use an index. */
-  pLoop = pLevel->pWLoop;
-  assert( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0 );
-  nEq = pLoop->u.btree.nEq;
-  nSkip = pLoop->u.btree.nSkip;
-  pIdx = pLoop->u.btree.pIndex;
-  assert( pIdx!=0 );
-
-  /* Figure out how many memory cells we will need then allocate them.
-  */
-  regBase = pParse->nMem + 1;
-  nReg = pLoop->u.btree.nEq + nExtraReg;
-  pParse->nMem += nReg;
-
-  zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
-  if( !zAff ){
-    pParse->db->mallocFailed = 1;
-  }
-
-  if( nSkip ){
-    int iIdxCur = pLevel->iIdxCur;
-    sqlite3VdbeAddOp1(v, (bRev?OP_Last:OP_Rewind), iIdxCur);
-    VdbeCoverageIf(v, bRev==0);
-    VdbeCoverageIf(v, bRev!=0);
-    VdbeComment((v, "begin skip-scan on %s", pIdx->zName));
-    j = sqlite3VdbeAddOp0(v, OP_Goto);
-    pLevel->addrSkip = sqlite3VdbeAddOp4Int(v, (bRev?OP_SeekLT:OP_SeekGT),
-                            iIdxCur, 0, regBase, nSkip);
-    VdbeCoverageIf(v, bRev==0);
-    VdbeCoverageIf(v, bRev!=0);
-    sqlite3VdbeJumpHere(v, j);
-    for(j=0; j<nSkip; j++){
-      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
-      assert( pIdx->aiColumn[j]>=0 );
-      VdbeComment((v, "%s", pIdx->pTable->aCol[pIdx->aiColumn[j]].zName));
-    }
-  }    
-
-  /* Evaluate the equality constraints
-  */
-  assert( zAff==0 || (int)strlen(zAff)>=nEq );
-  for(j=nSkip; j<nEq; j++){
-    int r1;
-    pTerm = pLoop->aLTerm[j];
-    assert( pTerm!=0 );
-    /* The following testcase is true for indices with redundant columns. 
-    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
-    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
-    testcase( pTerm->wtFlags & TERM_VIRTUAL );
-    r1 = codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, regBase+j);
-    if( r1!=regBase+j ){
-      if( nReg==1 ){
-        sqlite3ReleaseTempReg(pParse, regBase);
-        regBase = r1;
-      }else{
-        sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
-      }
-    }
-    testcase( pTerm->eOperator & WO_ISNULL );
-    testcase( pTerm->eOperator & WO_IN );
-    if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
-      Expr *pRight = pTerm->pExpr->pRight;
-      if( sqlite3ExprCanBeNull(pRight) ){
-        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
-        VdbeCoverage(v);
-      }
-      if( zAff ){
-        if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
-          zAff[j] = SQLITE_AFF_NONE;
-        }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
-          zAff[j] = SQLITE_AFF_NONE;
-        }
-      }
-    }
-  }
-  *pzAff = zAff;
-  return regBase;
-}
-
-#ifndef SQLITE_OMIT_EXPLAIN
-/*
-** This routine is a helper for explainIndexRange() below
-**
-** pStr holds the text of an expression that we are building up one term
-** at a time.  This routine adds a new term to the end of the expression.
-** Terms are separated by AND so add the "AND" text for second and subsequent
-** terms only.
-*/
-static void explainAppendTerm(
-  StrAccum *pStr,             /* The text expression being built */
-  int iTerm,                  /* Index of this term.  First is zero */
-  const char *zColumn,        /* Name of the column */
-  const char *zOp             /* Name of the operator */
-){
-  if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
-  sqlite3StrAccumAppendAll(pStr, zColumn);
-  sqlite3StrAccumAppend(pStr, zOp, 1);
-  sqlite3StrAccumAppend(pStr, "?", 1);
-}
-
-/*
-** Argument pLevel describes a strategy for scanning table pTab. This 
-** function appends text to pStr that describes the subset of table
-** rows scanned by the strategy in the form of an SQL expression.
-**
-** For example, if the query:
-**
-**   SELECT * FROM t1 WHERE a=1 AND b>2;
-**
-** is run and there is an index on (a, b), then this function returns a
-** string similar to:
-**
-**   "a=? AND b>?"
-*/
-static void explainIndexRange(StrAccum *pStr, WhereLoop *pLoop, Table *pTab){
-  Index *pIndex = pLoop->u.btree.pIndex;
-  u16 nEq = pLoop->u.btree.nEq;
-  u16 nSkip = pLoop->u.btree.nSkip;
-  int i, j;
-  Column *aCol = pTab->aCol;
-  i16 *aiColumn = pIndex->aiColumn;
-
-  if( nEq==0 && (pLoop->wsFlags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ) return;
-  sqlite3StrAccumAppend(pStr, " (", 2);
-  for(i=0; i<nEq; i++){
-    char *z = aiColumn[i] < 0 ? "rowid" : aCol[aiColumn[i]].zName;
-    if( i>=nSkip ){
-      explainAppendTerm(pStr, i, z, "=");
-    }else{
-      if( i ) sqlite3StrAccumAppend(pStr, " AND ", 5);
-      sqlite3XPrintf(pStr, 0, "ANY(%s)", z);
-    }
-  }
-
-  j = i;
-  if( pLoop->wsFlags&WHERE_BTM_LIMIT ){
-    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
-    explainAppendTerm(pStr, i++, z, ">");
-  }
-  if( pLoop->wsFlags&WHERE_TOP_LIMIT ){
-    char *z = aiColumn[j] < 0 ? "rowid" : aCol[aiColumn[j]].zName;
-    explainAppendTerm(pStr, i, z, "<");
-  }
-  sqlite3StrAccumAppend(pStr, ")", 1);
-}
-
-/*
-** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
-** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
-** record is added to the output to describe the table scan strategy in 
-** pLevel.
-*/
-static void explainOneScan(
-  Parse *pParse,                  /* Parse context */
-  SrcList *pTabList,              /* Table list this loop refers to */
-  WhereLevel *pLevel,             /* Scan to write OP_Explain opcode for */
-  int iLevel,                     /* Value for "level" column of output */
-  int iFrom,                      /* Value for "from" column of output */
-  u16 wctrlFlags                  /* Flags passed to sqlite3WhereBegin() */
-){
-#ifndef SQLITE_DEBUG
-  if( pParse->explain==2 )
-#endif
-  {
-    struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
-    Vdbe *v = pParse->pVdbe;      /* VM being constructed */
-    sqlite3 *db = pParse->db;     /* Database handle */
-    int iId = pParse->iSelectId;  /* Select id (left-most output column) */
-    int isSearch;                 /* True for a SEARCH. False for SCAN. */
-    WhereLoop *pLoop;             /* The controlling WhereLoop object */
-    u32 flags;                    /* Flags that describe this loop */
-    char *zMsg;                   /* Text to add to EQP output */
-    StrAccum str;                 /* EQP output string */
-    char zBuf[100];               /* Initial space for EQP output string */
-
-    pLoop = pLevel->pWLoop;
-    flags = pLoop->wsFlags;
-    if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return;
-
-    isSearch = (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
-            || ((flags&WHERE_VIRTUALTABLE)==0 && (pLoop->u.btree.nEq>0))
-            || (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
-
-    sqlite3StrAccumInit(&str, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
-    str.db = db;
-    sqlite3StrAccumAppendAll(&str, isSearch ? "SEARCH" : "SCAN");
-    if( pItem->pSelect ){
-      sqlite3XPrintf(&str, 0, " SUBQUERY %d", pItem->iSelectId);
-    }else{
-      sqlite3XPrintf(&str, 0, " TABLE %s", pItem->zName);
-    }
-
-    if( pItem->zAlias ){
-      sqlite3XPrintf(&str, 0, " AS %s", pItem->zAlias);
-    }
-    if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
-      const char *zFmt = 0;
-      Index *pIdx;
-
-      assert( pLoop->u.btree.pIndex!=0 );
-      pIdx = pLoop->u.btree.pIndex;
-      assert( !(flags&WHERE_AUTO_INDEX) || (flags&WHERE_IDX_ONLY) );
-      if( !HasRowid(pItem->pTab) && IsPrimaryKeyIndex(pIdx) ){
-        if( isSearch ){
-          zFmt = "PRIMARY KEY";
-        }
-      }else if( flags & WHERE_AUTO_INDEX ){
-        zFmt = "AUTOMATIC COVERING INDEX";
-      }else if( flags & WHERE_IDX_ONLY ){
-        zFmt = "COVERING INDEX %s";
-      }else{
-        zFmt = "INDEX %s";
-      }
-      if( zFmt ){
-        sqlite3StrAccumAppend(&str, " USING ", 7);
-        sqlite3XPrintf(&str, 0, zFmt, pIdx->zName);
-        explainIndexRange(&str, pLoop, pItem->pTab);
-      }
-    }else if( (flags & WHERE_IPK)!=0 && (flags & WHERE_CONSTRAINT)!=0 ){
-      const char *zRange;
-      if( flags&(WHERE_COLUMN_EQ|WHERE_COLUMN_IN) ){
-        zRange = "(rowid=?)";
-      }else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
-        zRange = "(rowid>? AND rowid<?)";
-      }else if( flags&WHERE_BTM_LIMIT ){
-        zRange = "(rowid>?)";
-      }else{
-        assert( flags&WHERE_TOP_LIMIT);
-        zRange = "(rowid<?)";
-      }
-      sqlite3StrAccumAppendAll(&str, " USING INTEGER PRIMARY KEY ");
-      sqlite3StrAccumAppendAll(&str, zRange);
-    }
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-    else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
-      sqlite3XPrintf(&str, 0, " VIRTUAL TABLE INDEX %d:%s",
-                  pLoop->u.vtab.idxNum, pLoop->u.vtab.idxStr);
-    }
-#endif
-#ifdef SQLITE_EXPLAIN_ESTIMATED_ROWS
-    if( pLoop->nOut>=10 ){
-      sqlite3XPrintf(&str, 0, " (~%llu rows)", sqlite3LogEstToInt(pLoop->nOut));
-    }else{
-      sqlite3StrAccumAppend(&str, " (~1 row)", 9);
-    }
-#endif
-    zMsg = sqlite3StrAccumFinish(&str);
-    sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg, P4_DYNAMIC);
-  }
-}
-#else
-# define explainOneScan(u,v,w,x,y,z)
-#endif /* SQLITE_OMIT_EXPLAIN */
-
-
-/*
-** Generate code for the start of the iLevel-th loop in the WHERE clause
-** implementation described by pWInfo.
-*/
-static Bitmask codeOneLoopStart(
-  WhereInfo *pWInfo,   /* Complete information about the WHERE clause */
-  int iLevel,          /* Which level of pWInfo->a[] should be coded */
-  Bitmask notReady     /* Which tables are currently available */
-){
-  int j, k;            /* Loop counters */
-  int iCur;            /* The VDBE cursor for the table */
-  int addrNxt;         /* Where to jump to continue with the next IN case */
-  int omitTable;       /* True if we use the index only */
-  int bRev;            /* True if we need to scan in reverse order */
-  WhereLevel *pLevel;  /* The where level to be coded */
-  WhereLoop *pLoop;    /* The WhereLoop object being coded */
-  WhereClause *pWC;    /* Decomposition of the entire WHERE clause */
-  WhereTerm *pTerm;               /* A WHERE clause term */
-  Parse *pParse;                  /* Parsing context */
-  sqlite3 *db;                    /* Database connection */
-  Vdbe *v;                        /* The prepared stmt under constructions */
-  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
-  int addrBrk;                    /* Jump here to break out of the loop */
-  int addrCont;                   /* Jump here to continue with next cycle */
-  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
-  int iReleaseReg = 0;      /* Temp register to free before returning */
-
-  pParse = pWInfo->pParse;
-  v = pParse->pVdbe;
-  pWC = &pWInfo->sWC;
-  db = pParse->db;
-  pLevel = &pWInfo->a[iLevel];
-  pLoop = pLevel->pWLoop;
-  pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
-  iCur = pTabItem->iCursor;
-  pLevel->notReady = notReady & ~getMask(&pWInfo->sMaskSet, iCur);
-  bRev = (pWInfo->revMask>>iLevel)&1;
-  omitTable = (pLoop->wsFlags & WHERE_IDX_ONLY)!=0 
-           && (pWInfo->wctrlFlags & WHERE_FORCE_TABLE)==0;
-  VdbeModuleComment((v, "Begin WHERE-loop%d: %s",iLevel,pTabItem->pTab->zName));
-
-  /* Create labels for the "break" and "continue" instructions
-  ** for the current loop.  Jump to addrBrk to break out of a loop.
-  ** Jump to cont to go immediately to the next iteration of the
-  ** loop.
-  **
-  ** When there is an IN operator, we also have a "addrNxt" label that
-  ** means to continue with the next IN value combination.  When
-  ** there are no IN operators in the constraints, the "addrNxt" label
-  ** is the same as "addrBrk".
-  */
-  addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
-  addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
-
-  /* If this is the right table of a LEFT OUTER JOIN, allocate and
-  ** initialize a memory cell that records if this table matches any
-  ** row of the left table of the join.
-  */
-  if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
-    pLevel->iLeftJoin = ++pParse->nMem;
-    sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
-    VdbeComment((v, "init LEFT JOIN no-match flag"));
-  }
-
-  /* Special case of a FROM clause subquery implemented as a co-routine */
-  if( pTabItem->viaCoroutine ){
-    int regYield = pTabItem->regReturn;
-    sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, pTabItem->addrFillSub);
-    pLevel->p2 =  sqlite3VdbeAddOp2(v, OP_Yield, regYield, addrBrk);
-    VdbeCoverage(v);
-    VdbeComment((v, "next row of \"%s\"", pTabItem->pTab->zName));
-    pLevel->op = OP_Goto;
-  }else
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-  if(  (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
-    /* Case 1:  The table is a virtual-table.  Use the VFilter and VNext
-    **          to access the data.
-    */
-    int iReg;   /* P3 Value for OP_VFilter */
-    int addrNotFound;
-    int nConstraint = pLoop->nLTerm;
-
-    sqlite3ExprCachePush(pParse);
-    iReg = sqlite3GetTempRange(pParse, nConstraint+2);
-    addrNotFound = pLevel->addrBrk;
-    for(j=0; j<nConstraint; j++){
-      int iTarget = iReg+j+2;
-      pTerm = pLoop->aLTerm[j];
-      if( pTerm==0 ) continue;
-      if( pTerm->eOperator & WO_IN ){
-        codeEqualityTerm(pParse, pTerm, pLevel, j, bRev, iTarget);
-        addrNotFound = pLevel->addrNxt;
-      }else{
-        sqlite3ExprCode(pParse, pTerm->pExpr->pRight, iTarget);
-      }
-    }
-    sqlite3VdbeAddOp2(v, OP_Integer, pLoop->u.vtab.idxNum, iReg);
-    sqlite3VdbeAddOp2(v, OP_Integer, nConstraint, iReg+1);
-    sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrNotFound, iReg,
-                      pLoop->u.vtab.idxStr,
-                      pLoop->u.vtab.needFree ? P4_MPRINTF : P4_STATIC);
-    VdbeCoverage(v);
-    pLoop->u.vtab.needFree = 0;
-    for(j=0; j<nConstraint && j<16; j++){
-      if( (pLoop->u.vtab.omitMask>>j)&1 ){
-        disableTerm(pLevel, pLoop->aLTerm[j]);
-      }
-    }
-    pLevel->op = OP_VNext;
-    pLevel->p1 = iCur;
-    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
-    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
-    sqlite3ExprCachePop(pParse);
-  }else
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-  if( (pLoop->wsFlags & WHERE_IPK)!=0
-   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
-  ){
-    /* Case 2:  We can directly reference a single row using an
-    **          equality comparison against the ROWID field.  Or
-    **          we reference multiple rows using a "rowid IN (...)"
-    **          construct.
-    */
-    assert( pLoop->u.btree.nEq==1 );
-    pTerm = pLoop->aLTerm[0];
-    assert( pTerm!=0 );
-    assert( pTerm->pExpr!=0 );
-    assert( omitTable==0 );
-    testcase( pTerm->wtFlags & TERM_VIRTUAL );
-    iReleaseReg = ++pParse->nMem;
-    iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, 0, bRev, iReleaseReg);
-    if( iRowidReg!=iReleaseReg ) sqlite3ReleaseTempReg(pParse, iReleaseReg);
-    addrNxt = pLevel->addrNxt;
-    sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt); VdbeCoverage(v);
-    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
-    VdbeCoverage(v);
-    sqlite3ExprCacheAffinityChange(pParse, iRowidReg, 1);
-    sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
-    VdbeComment((v, "pk"));
-    pLevel->op = OP_Noop;
-  }else if( (pLoop->wsFlags & WHERE_IPK)!=0
-         && (pLoop->wsFlags & WHERE_COLUMN_RANGE)!=0
-  ){
-    /* Case 3:  We have an inequality comparison against the ROWID field.
-    */
-    int testOp = OP_Noop;
-    int start;
-    int memEndValue = 0;
-    WhereTerm *pStart, *pEnd;
-
-    assert( omitTable==0 );
-    j = 0;
-    pStart = pEnd = 0;
-    if( pLoop->wsFlags & WHERE_BTM_LIMIT ) pStart = pLoop->aLTerm[j++];
-    if( pLoop->wsFlags & WHERE_TOP_LIMIT ) pEnd = pLoop->aLTerm[j++];
-    assert( pStart!=0 || pEnd!=0 );
-    if( bRev ){
-      pTerm = pStart;
-      pStart = pEnd;
-      pEnd = pTerm;
-    }
-    if( pStart ){
-      Expr *pX;             /* The expression that defines the start bound */
-      int r1, rTemp;        /* Registers for holding the start boundary */
-
-      /* The following constant maps TK_xx codes into corresponding 
-      ** seek opcodes.  It depends on a particular ordering of TK_xx
-      */
-      const u8 aMoveOp[] = {
-           /* TK_GT */  OP_SeekGT,
-           /* TK_LE */  OP_SeekLE,
-           /* TK_LT */  OP_SeekLT,
-           /* TK_GE */  OP_SeekGE
-      };
-      assert( TK_LE==TK_GT+1 );      /* Make sure the ordering.. */
-      assert( TK_LT==TK_GT+2 );      /*  ... of the TK_xx values... */
-      assert( TK_GE==TK_GT+3 );      /*  ... is correcct. */
-
-      assert( (pStart->wtFlags & TERM_VNULL)==0 );
-      testcase( pStart->wtFlags & TERM_VIRTUAL );
-      pX = pStart->pExpr;
-      assert( pX!=0 );
-      testcase( pStart->leftCursor!=iCur ); /* transitive constraints */
-      r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
-      sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
-      VdbeComment((v, "pk"));
-      VdbeCoverageIf(v, pX->op==TK_GT);
-      VdbeCoverageIf(v, pX->op==TK_LE);
-      VdbeCoverageIf(v, pX->op==TK_LT);
-      VdbeCoverageIf(v, pX->op==TK_GE);
-      sqlite3ExprCacheAffinityChange(pParse, r1, 1);
-      sqlite3ReleaseTempReg(pParse, rTemp);
-      disableTerm(pLevel, pStart);
-    }else{
-      sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
-      VdbeCoverageIf(v, bRev==0);
-      VdbeCoverageIf(v, bRev!=0);
-    }
-    if( pEnd ){
-      Expr *pX;
-      pX = pEnd->pExpr;
-      assert( pX!=0 );
-      assert( (pEnd->wtFlags & TERM_VNULL)==0 );
-      testcase( pEnd->leftCursor!=iCur ); /* Transitive constraints */
-      testcase( pEnd->wtFlags & TERM_VIRTUAL );
-      memEndValue = ++pParse->nMem;
-      sqlite3ExprCode(pParse, pX->pRight, memEndValue);
-      if( pX->op==TK_LT || pX->op==TK_GT ){
-        testOp = bRev ? OP_Le : OP_Ge;
-      }else{
-        testOp = bRev ? OP_Lt : OP_Gt;
-      }
-      disableTerm(pLevel, pEnd);
-    }
-    start = sqlite3VdbeCurrentAddr(v);
-    pLevel->op = bRev ? OP_Prev : OP_Next;
-    pLevel->p1 = iCur;
-    pLevel->p2 = start;
-    assert( pLevel->p5==0 );
-    if( testOp!=OP_Noop ){
-      iRowidReg = ++pParse->nMem;
-      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
-      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
-      sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
-      VdbeCoverageIf(v, testOp==OP_Le);
-      VdbeCoverageIf(v, testOp==OP_Lt);
-      VdbeCoverageIf(v, testOp==OP_Ge);
-      VdbeCoverageIf(v, testOp==OP_Gt);
-      sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
-    }
-  }else if( pLoop->wsFlags & WHERE_INDEXED ){
-    /* Case 4: A scan using an index.
-    **
-    **         The WHERE clause may contain zero or more equality 
-    **         terms ("==" or "IN" operators) that refer to the N
-    **         left-most columns of the index. It may also contain
-    **         inequality constraints (>, <, >= or <=) on the indexed
-    **         column that immediately follows the N equalities. Only 
-    **         the right-most column can be an inequality - the rest must
-    **         use the "==" and "IN" operators. For example, if the 
-    **         index is on (x,y,z), then the following clauses are all 
-    **         optimized:
-    **
-    **            x=5
-    **            x=5 AND y=10
-    **            x=5 AND y<10
-    **            x=5 AND y>5 AND y<10
-    **            x=5 AND y=5 AND z<=10
-    **
-    **         The z<10 term of the following cannot be used, only
-    **         the x=5 term:
-    **
-    **            x=5 AND z<10
-    **
-    **         N may be zero if there are inequality constraints.
-    **         If there are no inequality constraints, then N is at
-    **         least one.
-    **
-    **         This case is also used when there are no WHERE clause
-    **         constraints but an index is selected anyway, in order
-    **         to force the output order to conform to an ORDER BY.
-    */  
-    static const u8 aStartOp[] = {
-      0,
-      0,
-      OP_Rewind,           /* 2: (!start_constraints && startEq &&  !bRev) */
-      OP_Last,             /* 3: (!start_constraints && startEq &&   bRev) */
-      OP_SeekGT,           /* 4: (start_constraints  && !startEq && !bRev) */
-      OP_SeekLT,           /* 5: (start_constraints  && !startEq &&  bRev) */
-      OP_SeekGE,           /* 6: (start_constraints  &&  startEq && !bRev) */
-      OP_SeekLE            /* 7: (start_constraints  &&  startEq &&  bRev) */
-    };
-    static const u8 aEndOp[] = {
-      OP_IdxGE,            /* 0: (end_constraints && !bRev && !endEq) */
-      OP_IdxGT,            /* 1: (end_constraints && !bRev &&  endEq) */
-      OP_IdxLE,            /* 2: (end_constraints &&  bRev && !endEq) */
-      OP_IdxLT,            /* 3: (end_constraints &&  bRev &&  endEq) */
-    };
-    u16 nEq = pLoop->u.btree.nEq;     /* Number of == or IN terms */
-    int regBase;                 /* Base register holding constraint values */
-    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
-    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
-    int startEq;                 /* True if range start uses ==, >= or <= */
-    int endEq;                   /* True if range end uses ==, >= or <= */
-    int start_constraints;       /* Start of range is constrained */
-    int nConstraint;             /* Number of constraint terms */
-    Index *pIdx;                 /* The index we will be using */
-    int iIdxCur;                 /* The VDBE cursor for the index */
-    int nExtraReg = 0;           /* Number of extra registers needed */
-    int op;                      /* Instruction opcode */
-    char *zStartAff;             /* Affinity for start of range constraint */
-    char cEndAff = 0;            /* Affinity for end of range constraint */
-    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
-    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */
-
-    pIdx = pLoop->u.btree.pIndex;
-    iIdxCur = pLevel->iIdxCur;
-    assert( nEq>=pLoop->u.btree.nSkip );
-
-    /* If this loop satisfies a sort order (pOrderBy) request that 
-    ** was passed to this function to implement a "SELECT min(x) ..." 
-    ** query, then the caller will only allow the loop to run for
-    ** a single iteration. This means that the first row returned
-    ** should not have a NULL value stored in 'x'. If column 'x' is
-    ** the first one after the nEq equality constraints in the index,
-    ** this requires some special handling.
-    */
-    assert( pWInfo->pOrderBy==0
-         || pWInfo->pOrderBy->nExpr==1
-         || (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0 );
-    if( (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)!=0
-     && pWInfo->nOBSat>0
-     && (pIdx->nKeyCol>nEq)
-    ){
-      assert( pLoop->u.btree.nSkip==0 );
-      bSeekPastNull = 1;
-      nExtraReg = 1;
-    }
-
-    /* Find any inequality constraint terms for the start and end 
-    ** of the range. 
-    */
-    j = nEq;
-    if( pLoop->wsFlags & WHERE_BTM_LIMIT ){
-      pRangeStart = pLoop->aLTerm[j++];
-      nExtraReg = 1;
-    }
-    if( pLoop->wsFlags & WHERE_TOP_LIMIT ){
-      pRangeEnd = pLoop->aLTerm[j++];
-      nExtraReg = 1;
-      if( pRangeStart==0
-       && (j = pIdx->aiColumn[nEq])>=0 
-       && pIdx->pTable->aCol[j].notNull==0
-      ){
-        bSeekPastNull = 1;
-      }
-    }
-    assert( pRangeEnd==0 || (pRangeEnd->wtFlags & TERM_VNULL)==0 );
-
-    /* Generate code to evaluate all constraint terms using == or IN
-    ** and store the values of those terms in an array of registers
-    ** starting at regBase.
-    */
-    regBase = codeAllEqualityTerms(pParse,pLevel,bRev,nExtraReg,&zStartAff);
-    assert( zStartAff==0 || sqlite3Strlen30(zStartAff)>=nEq );
-    if( zStartAff ) cEndAff = zStartAff[nEq];
-    addrNxt = pLevel->addrNxt;
-
-    /* If we are doing a reverse order scan on an ascending index, or
-    ** a forward order scan on a descending index, interchange the 
-    ** start and end terms (pRangeStart and pRangeEnd).
-    */
-    if( (nEq<pIdx->nKeyCol && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC))
-     || (bRev && pIdx->nKeyCol==nEq)
-    ){
-      SWAP(WhereTerm *, pRangeEnd, pRangeStart);
-      SWAP(u8, bSeekPastNull, bStopAtNull);
-    }
-
-    testcase( pRangeStart && (pRangeStart->eOperator & WO_LE)!=0 );
-    testcase( pRangeStart && (pRangeStart->eOperator & WO_GE)!=0 );
-    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_LE)!=0 );
-    testcase( pRangeEnd && (pRangeEnd->eOperator & WO_GE)!=0 );
-    startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
-    endEq =   !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
-    start_constraints = pRangeStart || nEq>0;
-
-    /* Seek the index cursor to the start of the range. */
-    nConstraint = nEq;
-    if( pRangeStart ){
-      Expr *pRight = pRangeStart->pExpr->pRight;
-      sqlite3ExprCode(pParse, pRight, regBase+nEq);
-      if( (pRangeStart->wtFlags & TERM_VNULL)==0
-       && sqlite3ExprCanBeNull(pRight)
-      ){
-        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
-        VdbeCoverage(v);
-      }
-      if( zStartAff ){
-        if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
-          /* Since the comparison is to be performed with no conversions
-          ** applied to the operands, set the affinity to apply to pRight to 
-          ** SQLITE_AFF_NONE.  */
-          zStartAff[nEq] = SQLITE_AFF_NONE;
-        }
-        if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
-          zStartAff[nEq] = SQLITE_AFF_NONE;
-        }
-      }  
-      nConstraint++;
-      testcase( pRangeStart->wtFlags & TERM_VIRTUAL );
-    }else if( bSeekPastNull ){
-      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
-      nConstraint++;
-      startEq = 0;
-      start_constraints = 1;
-    }
-    codeApplyAffinity(pParse, regBase, nConstraint - bSeekPastNull, zStartAff);
-    op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
-    assert( op!=0 );
-    sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
-    VdbeCoverage(v);
-    VdbeCoverageIf(v, op==OP_Rewind);  testcase( op==OP_Rewind );
-    VdbeCoverageIf(v, op==OP_Last);    testcase( op==OP_Last );
-    VdbeCoverageIf(v, op==OP_SeekGT);  testcase( op==OP_SeekGT );
-    VdbeCoverageIf(v, op==OP_SeekGE);  testcase( op==OP_SeekGE );
-    VdbeCoverageIf(v, op==OP_SeekLE);  testcase( op==OP_SeekLE );
-    VdbeCoverageIf(v, op==OP_SeekLT);  testcase( op==OP_SeekLT );
-
-    /* Load the value for the inequality constraint at the end of the
-    ** range (if any).
-    */
-    nConstraint = nEq;
-    if( pRangeEnd ){
-      Expr *pRight = pRangeEnd->pExpr->pRight;
-      sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
-      sqlite3ExprCode(pParse, pRight, regBase+nEq);
-      if( (pRangeEnd->wtFlags & TERM_VNULL)==0
-       && sqlite3ExprCanBeNull(pRight)
-      ){
-        sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
-        VdbeCoverage(v);
-      }
-      if( sqlite3CompareAffinity(pRight, cEndAff)!=SQLITE_AFF_NONE
-       && !sqlite3ExprNeedsNoAffinityChange(pRight, cEndAff)
-      ){
-        codeApplyAffinity(pParse, regBase+nEq, 1, &cEndAff);
-      }
-      nConstraint++;
-      testcase( pRangeEnd->wtFlags & TERM_VIRTUAL );
-    }else if( bStopAtNull ){
-      sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
-      endEq = 0;
-      nConstraint++;
-    }
-    sqlite3DbFree(db, zStartAff);
-
-    /* Top of the loop body */
-    pLevel->p2 = sqlite3VdbeCurrentAddr(v);
-
-    /* Check if the index cursor is past the end of the range. */
-    if( nConstraint ){
-      op = aEndOp[bRev*2 + endEq];
-      sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
-      testcase( op==OP_IdxGT );  VdbeCoverageIf(v, op==OP_IdxGT );
-      testcase( op==OP_IdxGE );  VdbeCoverageIf(v, op==OP_IdxGE );
-      testcase( op==OP_IdxLT );  VdbeCoverageIf(v, op==OP_IdxLT );
-      testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
-    }
-
-    /* Seek the table cursor, if required */
-    disableTerm(pLevel, pRangeStart);
-    disableTerm(pLevel, pRangeEnd);
-    if( omitTable ){
-      /* pIdx is a covering index.  No need to access the main table. */
-    }else if( HasRowid(pIdx->pTable) ){
-      iRowidReg = ++pParse->nMem;
-      sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
-      sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
-      sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg);  /* Deferred seek */
-    }else if( iCur!=iIdxCur ){
-      Index *pPk = sqlite3PrimaryKeyIndex(pIdx->pTable);
-      iRowidReg = sqlite3GetTempRange(pParse, pPk->nKeyCol);
-      for(j=0; j<pPk->nKeyCol; j++){
-        k = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[j]);
-        sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, k, iRowidReg+j);
-      }
-      sqlite3VdbeAddOp4Int(v, OP_NotFound, iCur, addrCont,
-                           iRowidReg, pPk->nKeyCol); VdbeCoverage(v);
-    }
-
-    /* Record the instruction used to terminate the loop. Disable 
-    ** WHERE clause terms made redundant by the index range scan.
-    */
-    if( pLoop->wsFlags & WHERE_ONEROW ){
-      pLevel->op = OP_Noop;
-    }else if( bRev ){
-      pLevel->op = OP_Prev;
-    }else{
-      pLevel->op = OP_Next;
-    }
-    pLevel->p1 = iIdxCur;
-    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
-    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
-      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
-    }else{
-      assert( pLevel->p5==0 );
-    }
-  }else
-
-#ifndef SQLITE_OMIT_OR_OPTIMIZATION
-  if( pLoop->wsFlags & WHERE_MULTI_OR ){
-    /* Case 5:  Two or more separately indexed terms connected by OR
-    **
-    ** Example:
-    **
-    **   CREATE TABLE t1(a,b,c,d);
-    **   CREATE INDEX i1 ON t1(a);
-    **   CREATE INDEX i2 ON t1(b);
-    **   CREATE INDEX i3 ON t1(c);
-    **
-    **   SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
-    **
-    ** In the example, there are three indexed terms connected by OR.
-    ** The top of the loop looks like this:
-    **
-    **          Null       1                # Zero the rowset in reg 1
-    **
-    ** Then, for each indexed term, the following. The arguments to
-    ** RowSetTest are such that the rowid of the current row is inserted
-    ** into the RowSet. If it is already present, control skips the
-    ** Gosub opcode and jumps straight to the code generated by WhereEnd().
-    **
-    **        sqlite3WhereBegin(<term>)
-    **          RowSetTest                  # Insert rowid into rowset
-    **          Gosub      2 A
-    **        sqlite3WhereEnd()
-    **
-    ** Following the above, code to terminate the loop. Label A, the target
-    ** of the Gosub above, jumps to the instruction right after the Goto.
-    **
-    **          Null       1                # Zero the rowset in reg 1
-    **          Goto       B                # The loop is finished.
-    **
-    **       A: <loop body>                 # Return data, whatever.
-    **
-    **          Return     2                # Jump back to the Gosub
-    **
-    **       B: <after the loop>
-    **
-    ** Added 2014-05-26: If the table is a WITHOUT ROWID table, then
-    ** use an ephemeral index instead of a RowSet to record the primary
-    ** keys of the rows we have already seen.
-    **
-    */
-    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
-    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
-    Index *pCov = 0;             /* Potential covering index (or NULL) */
-    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */
-
-    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
-    int regRowset = 0;                        /* Register for RowSet object */
-    int regRowid = 0;                         /* Register holding rowid */
-    int iLoopBody = sqlite3VdbeMakeLabel(v);  /* Start of loop body */
-    int iRetInit;                             /* Address of regReturn init */
-    int untestedTerms = 0;             /* Some terms not completely tested */
-    int ii;                            /* Loop counter */
-    u16 wctrlFlags;                    /* Flags for sub-WHERE clause */
-    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
-    Table *pTab = pTabItem->pTab;
-   
-    pTerm = pLoop->aLTerm[0];
-    assert( pTerm!=0 );
-    assert( pTerm->eOperator & WO_OR );
-    assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
-    pOrWc = &pTerm->u.pOrInfo->wc;
-    pLevel->op = OP_Return;
-    pLevel->p1 = regReturn;
-
-    /* Set up a new SrcList in pOrTab containing the table being scanned
-    ** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
-    ** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
-    */
-    if( pWInfo->nLevel>1 ){
-      int nNotReady;                 /* The number of notReady tables */
-      struct SrcList_item *origSrc;     /* Original list of tables */
-      nNotReady = pWInfo->nLevel - iLevel - 1;
-      pOrTab = sqlite3StackAllocRaw(db,
-                            sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
-      if( pOrTab==0 ) return notReady;
-      pOrTab->nAlloc = (u8)(nNotReady + 1);
-      pOrTab->nSrc = pOrTab->nAlloc;
-      memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
-      origSrc = pWInfo->pTabList->a;
-      for(k=1; k<=nNotReady; k++){
-        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
-      }
-    }else{
-      pOrTab = pWInfo->pTabList;
-    }
-
-    /* Initialize the rowset register to contain NULL. An SQL NULL is 
-    ** equivalent to an empty rowset.  Or, create an ephemeral index
-    ** capable of holding primary keys in the case of a WITHOUT ROWID.
-    **
-    ** Also initialize regReturn to contain the address of the instruction 
-    ** immediately following the OP_Return at the bottom of the loop. This
-    ** is required in a few obscure LEFT JOIN cases where control jumps
-    ** over the top of the loop into the body of it. In this case the 
-    ** correct response for the end-of-loop code (the OP_Return) is to 
-    ** fall through to the next instruction, just as an OP_Next does if
-    ** called on an uninitialized cursor.
-    */
-    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
-      if( HasRowid(pTab) ){
-        regRowset = ++pParse->nMem;
-        sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
-      }else{
-        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
-        regRowset = pParse->nTab++;
-        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, regRowset, pPk->nKeyCol);
-        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
-      }
-      regRowid = ++pParse->nMem;
-    }
-    iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
-
-    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
-    ** Then for every term xN, evaluate as the subexpression: xN AND z
-    ** That way, terms in y that are factored into the disjunction will
-    ** be picked up by the recursive calls to sqlite3WhereBegin() below.
-    **
-    ** Actually, each subexpression is converted to "xN AND w" where w is
-    ** the "interesting" terms of z - terms that did not originate in the
-    ** ON or USING clause of a LEFT JOIN, and terms that are usable as 
-    ** indices.
-    **
-    ** This optimization also only applies if the (x1 OR x2 OR ...) term
-    ** is not contained in the ON clause of a LEFT JOIN.
-    ** See ticket http://www.sqlite.org/src/info/f2369304e4
-    */
-    if( pWC->nTerm>1 ){
-      int iTerm;
-      for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
-        Expr *pExpr = pWC->a[iTerm].pExpr;
-        if( &pWC->a[iTerm] == pTerm ) continue;
-        if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
-        testcase( pWC->a[iTerm].wtFlags & TERM_ORINFO );
-        testcase( pWC->a[iTerm].wtFlags & TERM_VIRTUAL );
-        if( pWC->a[iTerm].wtFlags & (TERM_ORINFO|TERM_VIRTUAL) ) continue;
-        if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
-        pExpr = sqlite3ExprDup(db, pExpr, 0);
-        pAndExpr = sqlite3ExprAnd(db, pAndExpr, pExpr);
-      }
-      if( pAndExpr ){
-        pAndExpr = sqlite3PExpr(pParse, TK_AND, 0, pAndExpr, 0);
-      }
-    }
-
-    /* Run a separate WHERE clause for each term of the OR clause.  After
-    ** eliminating duplicates from other WHERE clauses, the action for each
-    ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
-    */
-    wctrlFlags =  WHERE_OMIT_OPEN_CLOSE
-                | WHERE_FORCE_TABLE
-                | WHERE_ONETABLE_ONLY;
-    for(ii=0; ii<pOrWc->nTerm; ii++){
-      WhereTerm *pOrTerm = &pOrWc->a[ii];
-      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
-        WhereInfo *pSubWInfo;           /* Info for single OR-term scan */
-        Expr *pOrExpr = pOrTerm->pExpr; /* Current OR clause term */
-        int j1 = 0;                     /* Address of jump operation */
-        if( pAndExpr && !ExprHasProperty(pOrExpr, EP_FromJoin) ){
-          pAndExpr->pLeft = pOrExpr;
-          pOrExpr = pAndExpr;
-        }
-        /* Loop through table entries that match term pOrTerm. */
-        WHERETRACE(0xffff, ("Subplan for OR-clause:\n"));
-        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
-                                      wctrlFlags, iCovCur);
-        assert( pSubWInfo || pParse->nErr || db->mallocFailed );
-        if( pSubWInfo ){
-          WhereLoop *pSubLoop;
-          explainOneScan(
-              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
-          );
-          /* This is the sub-WHERE clause body.  First skip over
-          ** duplicate rows from prior sub-WHERE clauses, and record the
-          ** rowid (or PRIMARY KEY) for the current row so that the same
-          ** row will be skipped in subsequent sub-WHERE clauses.
-          */
-          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
-            int r;
-            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
-            if( HasRowid(pTab) ){
-              r = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, regRowid, 0);
-              j1 = sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset, 0, r,iSet);
-              VdbeCoverage(v);
-            }else{
-              Index *pPk = sqlite3PrimaryKeyIndex(pTab);
-              int nPk = pPk->nKeyCol;
-              int iPk;
-
-              /* Read the PK into an array of temp registers. */
-              r = sqlite3GetTempRange(pParse, nPk);
-              for(iPk=0; iPk<nPk; iPk++){
-                int iCol = pPk->aiColumn[iPk];
-                sqlite3ExprCodeGetColumn(pParse, pTab, iCol, iCur, r+iPk, 0);
-              }
-
-              /* Check if the temp table already contains this key. If so,
-              ** the row has already been included in the result set and
-              ** can be ignored (by jumping past the Gosub below). Otherwise,
-              ** insert the key into the temp table and proceed with processing
-              ** the row.
-              **
-              ** Use some of the same optimizations as OP_RowSetTest: If iSet
-              ** is zero, assume that the key cannot already be present in
-              ** the temp table. And if iSet is -1, assume that there is no 
-              ** need to insert the key into the temp table, as it will never 
-              ** be tested for.  */ 
-              if( iSet ){
-                j1 = sqlite3VdbeAddOp4Int(v, OP_Found, regRowset, 0, r, nPk);
-                VdbeCoverage(v);
-              }
-              if( iSet>=0 ){
-                sqlite3VdbeAddOp3(v, OP_MakeRecord, r, nPk, regRowid);
-                sqlite3VdbeAddOp3(v, OP_IdxInsert, regRowset, regRowid, 0);
-                if( iSet ) sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
-              }
-
-              /* Release the array of temp registers */
-              sqlite3ReleaseTempRange(pParse, r, nPk);
-            }
-          }
-
-          /* Invoke the main loop body as a subroutine */
-          sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
-
-          /* Jump here (skipping the main loop body subroutine) if the
-          ** current sub-WHERE row is a duplicate from prior sub-WHEREs. */
-          if( j1 ) sqlite3VdbeJumpHere(v, j1);
-
-          /* The pSubWInfo->untestedTerms flag means that this OR term
-          ** contained one or more AND term from a notReady table.  The
-          ** terms from the notReady table could not be tested and will
-          ** need to be tested later.
-          */
-          if( pSubWInfo->untestedTerms ) untestedTerms = 1;
-
-          /* If all of the OR-connected terms are optimized using the same
-          ** index, and the index is opened using the same cursor number
-          ** by each call to sqlite3WhereBegin() made by this loop, it may
-          ** be possible to use that index as a covering index.
-          **
-          ** If the call to sqlite3WhereBegin() above resulted in a scan that
-          ** uses an index, and this is either the first OR-connected term
-          ** processed or the index is the same as that used by all previous
-          ** terms, set pCov to the candidate covering index. Otherwise, set 
-          ** pCov to NULL to indicate that no candidate covering index will 
-          ** be available.
-          */
-          pSubLoop = pSubWInfo->a[0].pWLoop;
-          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
-          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
-           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
-           && (HasRowid(pTab) || !IsPrimaryKeyIndex(pSubLoop->u.btree.pIndex))
-          ){
-            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
-            pCov = pSubLoop->u.btree.pIndex;
-            wctrlFlags |= WHERE_REOPEN_IDX;
-          }else{
-            pCov = 0;
-          }
-
-          /* Finish the loop through table entries that match term pOrTerm. */
-          sqlite3WhereEnd(pSubWInfo);
-        }
-      }
-    }
-    pLevel->u.pCovidx = pCov;
-    if( pCov ) pLevel->iIdxCur = iCovCur;
-    if( pAndExpr ){
-      pAndExpr->pLeft = 0;
-      sqlite3ExprDelete(db, pAndExpr);
-    }
-    sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
-    sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
-    sqlite3VdbeResolveLabel(v, iLoopBody);
-
-    if( pWInfo->nLevel>1 ) sqlite3StackFree(db, pOrTab);
-    if( !untestedTerms ) disableTerm(pLevel, pTerm);
-  }else
-#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
-
-  {
-    /* Case 6:  There is no usable index.  We must do a complete
-    **          scan of the entire table.
-    */
-    static const u8 aStep[] = { OP_Next, OP_Prev };
-    static const u8 aStart[] = { OP_Rewind, OP_Last };
-    assert( bRev==0 || bRev==1 );
-    if( pTabItem->isRecursive ){
-      /* Tables marked isRecursive have only a single row that is stored in
-      ** a pseudo-cursor.  No need to Rewind or Next such cursors. */
-      pLevel->op = OP_Noop;
-    }else{
-      pLevel->op = aStep[bRev];
-      pLevel->p1 = iCur;
-      pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
-      VdbeCoverageIf(v, bRev==0);
-      VdbeCoverageIf(v, bRev!=0);
-      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
-    }
-  }
-
-  /* Insert code to test every subexpression that can be completely
-  ** computed using the current set of tables.
-  */
-  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
-    Expr *pE;
-    testcase( pTerm->wtFlags & TERM_VIRTUAL );
-    testcase( pTerm->wtFlags & TERM_CODED );
-    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-    if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
-      testcase( pWInfo->untestedTerms==0
-               && (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
-      pWInfo->untestedTerms = 1;
-      continue;
-    }
-    pE = pTerm->pExpr;
-    assert( pE!=0 );
-    if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
-      continue;
-    }
-    sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
-    pTerm->wtFlags |= TERM_CODED;
-  }
-
-  /* Insert code to test for implied constraints based on transitivity
-  ** of the "==" operator.
-  **
-  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
-  ** and we are coding the t1 loop and the t2 loop has not yet coded,
-  ** then we cannot use the "t1.a=t2.b" constraint, but we can code
-  ** the implied "t1.a=123" constraint.
-  */
-  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
-    Expr *pE, *pEAlt;
-    WhereTerm *pAlt;
-    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-    if( pTerm->eOperator!=(WO_EQUIV|WO_EQ) ) continue;
-    if( pTerm->leftCursor!=iCur ) continue;
-    if( pLevel->iLeftJoin ) continue;
-    pE = pTerm->pExpr;
-    assert( !ExprHasProperty(pE, EP_FromJoin) );
-    assert( (pTerm->prereqRight & pLevel->notReady)!=0 );
-    pAlt = findTerm(pWC, iCur, pTerm->u.leftColumn, notReady, WO_EQ|WO_IN, 0);
-    if( pAlt==0 ) continue;
-    if( pAlt->wtFlags & (TERM_CODED) ) continue;
-    testcase( pAlt->eOperator & WO_EQ );
-    testcase( pAlt->eOperator & WO_IN );
-    VdbeModuleComment((v, "begin transitive constraint"));
-    pEAlt = sqlite3StackAllocRaw(db, sizeof(*pEAlt));
-    if( pEAlt ){
-      *pEAlt = *pAlt->pExpr;
-      pEAlt->pLeft = pE->pLeft;
-      sqlite3ExprIfFalse(pParse, pEAlt, addrCont, SQLITE_JUMPIFNULL);
-      sqlite3StackFree(db, pEAlt);
-    }
-  }
-
-  /* For a LEFT OUTER JOIN, generate code that will record the fact that
-  ** at least one row of the right table has matched the left table.  
-  */
-  if( pLevel->iLeftJoin ){
-    pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
-    sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
-    VdbeComment((v, "record LEFT JOIN hit"));
-    sqlite3ExprCacheClear(pParse);
-    for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
-      testcase( pTerm->wtFlags & TERM_VIRTUAL );
-      testcase( pTerm->wtFlags & TERM_CODED );
-      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
-      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
-        assert( pWInfo->untestedTerms );
-        continue;
-      }
-      assert( pTerm->pExpr );
-      sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
-      pTerm->wtFlags |= TERM_CODED;
-    }
-  }
-
-  return pLevel->notReady;
-}
 
 #ifdef WHERETRACE_ENABLED
 /*
 ** Print the content of a WhereTerm object
 */
 static void whereTermPrint(WhereTerm *pTerm, int iTerm){
   if( pTerm==0 ){
     sqlite3DebugPrintf("TERM-%-3d NULL\n", iTerm);
   }else{
     char zType[4];
     memcpy(zType, "...", 4);
     if( pTerm->wtFlags & TERM_VIRTUAL ) zType[0] = 'V';
     if( pTerm->eOperator & WO_EQUIV  ) zType[1] = 'E';
     if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) zType[2] = 'L';
-    sqlite3DebugPrintf("TERM-%-3d %p %s cursor=%-3d prob=%-3d op=0x%03x\n",
-                       iTerm, pTerm, zType, pTerm->leftCursor, pTerm->truthProb,
-                       pTerm->eOperator);
+    sqlite3DebugPrintf(
+       "TERM-%-3d %p %s cursor=%-3d prob=%-3d op=0x%03x wtFlags=0x%04x\n",
+       iTerm, pTerm, zType, pTerm->leftCursor, pTerm->truthProb,
+       pTerm->eOperator, pTerm->wtFlags);
     sqlite3TreeViewExpr(0, pTerm->pExpr, 0);
   }
 }
 #endif
 
 #ifdef WHERETRACE_ENABLED
 /*
 ** Print a WhereLoop object for debugging purposes
 */
 static void whereLoopPrint(WhereLoop *p, WhereClause *pWC){
@@ skipping 22 matching lines @@
     if( p->u.vtab.idxStr ){
       z = sqlite3_mprintf("(%d,\"%s\",%x)",
                 p->u.vtab.idxNum, p->u.vtab.idxStr, p->u.vtab.omitMask);
     }else{
       z = sqlite3_mprintf("(%d,%x)", p->u.vtab.idxNum, p->u.vtab.omitMask);
     }
     sqlite3DebugPrintf(" %-19s", z);
     sqlite3_free(z);
   }
   if( p->wsFlags & WHERE_SKIPSCAN ){
-    sqlite3DebugPrintf(" f %05x %d-%d", p->wsFlags, p->nLTerm,p->u.btree.nSkip);
+    sqlite3DebugPrintf(" f %05x %d-%d", p->wsFlags, p->nLTerm,p->nSkip);
   }else{
     sqlite3DebugPrintf(" f %05x N %d", p->wsFlags, p->nLTerm);
   }
   sqlite3DebugPrintf(" cost %d,%d,%d\n", p->rSetup, p->rRun, p->nOut);
   if( p->nLTerm && (sqlite3WhereTrace & 0x100)!=0 ){
     int i;
     for(i=0; i<p->nLTerm; i++){
       whereTermPrint(p->aLTerm[i], i);
     }
   }
@@ skipping 15 matching lines @@
 ** Clear the WhereLoop.u union.  Leave WhereLoop.pLTerm intact.
 */
 static void whereLoopClearUnion(sqlite3 *db, WhereLoop *p){
   if( p->wsFlags & (WHERE_VIRTUALTABLE|WHERE_AUTO_INDEX) ){
     if( (p->wsFlags & WHERE_VIRTUALTABLE)!=0 && p->u.vtab.needFree ){
       sqlite3_free(p->u.vtab.idxStr);
       p->u.vtab.needFree = 0;
       p->u.vtab.idxStr = 0;
     }else if( (p->wsFlags & WHERE_AUTO_INDEX)!=0 && p->u.btree.pIndex!=0 ){
       sqlite3DbFree(db, p->u.btree.pIndex->zColAff);
-      sqlite3KeyInfoUnref(p->u.btree.pIndex->pKeyInfo);
       sqlite3DbFree(db, p->u.btree.pIndex);
       p->u.btree.pIndex = 0;
     }
   }
 }
 
 /*
 ** Deallocate internal memory used by a WhereLoop object
 */
 static void whereLoopClear(sqlite3 *db, WhereLoop *p){
@@ skipping 43 matching lines @@
 static void whereLoopDelete(sqlite3 *db, WhereLoop *p){
   whereLoopClear(db, p);
   sqlite3DbFree(db, p);
 }
 
 /*
 ** Free a WhereInfo structure
 */
 static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
   if( ALWAYS(pWInfo) ){
-    whereClauseClear(&pWInfo->sWC);
+    int i;
+    for(i=0; i<pWInfo->nLevel; i++){
+      WhereLevel *pLevel = &pWInfo->a[i];
+      if( pLevel->pWLoop && (pLevel->pWLoop->wsFlags & WHERE_IN_ABLE) ){
+        sqlite3DbFree(db, pLevel->u.in.aInLoop);
+      }
+    }
+    sqlite3WhereClauseClear(&pWInfo->sWC);
     while( pWInfo->pLoops ){
       WhereLoop *p = pWInfo->pLoops;
       pWInfo->pLoops = p->pNextLoop;
       whereLoopDelete(db, p);
     }
     sqlite3DbFree(db, pWInfo);
   }
 }
 
 /*
-** Return TRUE if both of the following are true:
+** Return TRUE if all of the following are true:
 **
 **   (1)  X has the same or lower cost that Y
 **   (2)  X is a proper subset of Y
+**   (3)  X skips at least as many columns as Y
 **
 ** By "proper subset" we mean that X uses fewer WHERE clause terms
 ** than Y and that every WHERE clause term used by X is also used
 ** by Y.
 **
 ** If X is a proper subset of Y then Y is a better choice and ought
 ** to have a lower cost.  This routine returns TRUE when that cost 
-** relationship is inverted and needs to be adjusted.
+** relationship is inverted and needs to be adjusted.  The third rule
+** was added because if X uses skip-scan less than Y it still might
+** deserve a lower cost even if it is a proper subset of Y.
 */
 static int whereLoopCheaperProperSubset(
   const WhereLoop *pX,       /* First WhereLoop to compare */
   const WhereLoop *pY        /* Compare against this WhereLoop */
 ){
   int i, j;
-  if( pX->nLTerm >= pY->nLTerm ) return 0; /* X is not a subset of Y */
+  if( pX->nLTerm-pX->nSkip >= pY->nLTerm-pY->nSkip ){
+    return 0; /* X is not a subset of Y */
+  }
+  if( pY->nSkip > pX->nSkip ) return 0;
   if( pX->rRun >= pY->rRun ){
     if( pX->rRun > pY->rRun ) return 0;    /* X costs more than Y */
     if( pX->nOut > pY->nOut ) return 0;    /* X costs more than Y */
   }
   for(i=pX->nLTerm-1; i>=0; i--){
+    if( pX->aLTerm[i]==0 ) continue;
     for(j=pY->nLTerm-1; j>=0; j--){
       if( pY->aLTerm[j]==pX->aLTerm[i] ) break;
     }
     if( j<0 ) return 0;  /* X not a subset of Y since term X[i] not used by Y */
   }
   return 1;  /* All conditions meet */
 }
 
 /*
 ** Try to adjust the cost of WhereLoop pTemplate upwards or downwards so
 ** that:
 **
 **   (1) pTemplate costs less than any other WhereLoops that are a proper
 **       subset of pTemplate
 **
 **   (2) pTemplate costs more than any other WhereLoops for which pTemplate
 **       is a proper subset.
 **
 ** To say "WhereLoop X is a proper subset of Y" means that X uses fewer
 ** WHERE clause terms than Y and that every WHERE clause term used by X is
 ** also used by Y.
-**
-** This adjustment is omitted for SKIPSCAN loops.  In a SKIPSCAN loop, the
-** WhereLoop.nLTerm field is not an accurate measure of the number of WHERE
-** clause terms covered, since some of the first nLTerm entries in aLTerm[]
-** will be NULL (because they are skipped).  That makes it more difficult
-** to compare the loops.  We could add extra code to do the comparison, and
-** perhaps we will someday.  But SKIPSCAN is sufficiently uncommon, and this
-** adjustment is sufficient minor, that it is very difficult to construct
-** a test case where the extra code would improve the query plan.  Better
-** to avoid the added complexity and just omit cost adjustments to SKIPSCAN
-** loops.
 */
 static void whereLoopAdjustCost(const WhereLoop *p, WhereLoop *pTemplate){
   if( (pTemplate->wsFlags & WHERE_INDEXED)==0 ) return;
-  if( (pTemplate->wsFlags & WHERE_SKIPSCAN)!=0 ) return;
   for(; p; p=p->pNextLoop){
     if( p->iTab!=pTemplate->iTab ) continue;
     if( (p->wsFlags & WHERE_INDEXED)==0 ) continue;
-    if( (p->wsFlags & WHERE_SKIPSCAN)!=0 ) continue;
     if( whereLoopCheaperProperSubset(p, pTemplate) ){
       /* Adjust pTemplate cost downward so that it is cheaper than its 
-      ** subset p */
+      ** subset p. */
+      WHERETRACE(0x80,("subset cost adjustment %d,%d to %d,%d\n",
+                       pTemplate->rRun, pTemplate->nOut, p->rRun, p->nOut-1));
       pTemplate->rRun = p->rRun;
       pTemplate->nOut = p->nOut - 1;
     }else if( whereLoopCheaperProperSubset(pTemplate, p) ){
       /* Adjust pTemplate cost upward so that it is costlier than p since
       ** pTemplate is a proper subset of p */
+      WHERETRACE(0x80,("subset cost adjustment %d,%d to %d,%d\n",
+                       pTemplate->rRun, pTemplate->nOut, p->rRun, p->nOut+1));
       pTemplate->rRun = p->rRun;
       pTemplate->nOut = p->nOut + 1;
     }
   }
 }
 
 /*
 ** Search the list of WhereLoops in *ppPrev looking for one that can be
 ** supplanted by pTemplate.
 **
@@ skipping 24 matching lines @@
     assert( p->rSetup==0 || pTemplate->rSetup==0 
                  || p->rSetup==pTemplate->rSetup );
 
     /* whereLoopAddBtree() always generates and inserts the automatic index
     ** case first.  Hence compatible candidate WhereLoops never have a larger
     ** rSetup. Call this SETUP-INVARIANT */
     assert( p->rSetup>=pTemplate->rSetup );
 
     /* Any loop using an appliation-defined index (or PRIMARY KEY or
     ** UNIQUE constraint) with one or more == constraints is better
-    ** than an automatic index. */
+    ** than an automatic index. Unless it is a skip-scan. */
     if( (p->wsFlags & WHERE_AUTO_INDEX)!=0
+     && (pTemplate->nSkip)==0
      && (pTemplate->wsFlags & WHERE_INDEXED)!=0
      && (pTemplate->wsFlags & WHERE_COLUMN_EQ)!=0
      && (p->prereq & pTemplate->prereq)==pTemplate->prereq
     ){
       break;
     }
 
     /* If existing WhereLoop p is better than pTemplate, pTemplate can be
     ** discarded.  WhereLoop p is better if:
     **   (1)  p has no more dependencies than pTemplate, and
@@ skipping 49 matching lines @@
 */
 static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
   WhereLoop **ppPrev, *p;
   WhereInfo *pWInfo = pBuilder->pWInfo;
   sqlite3 *db = pWInfo->pParse->db;
 
   /* If pBuilder->pOrSet is defined, then only keep track of the costs
   ** and prereqs.
   */
   if( pBuilder->pOrSet!=0 ){
+    if( pTemplate->nLTerm ){
 #if WHERETRACE_ENABLED
-    u16 n = pBuilder->pOrSet->n;
-    int x =
+      u16 n = pBuilder->pOrSet->n;
+      int x =
 #endif
-    whereOrInsert(pBuilder->pOrSet, pTemplate->prereq, pTemplate->rRun,
+      whereOrInsert(pBuilder->pOrSet, pTemplate->prereq, pTemplate->rRun,
                                     pTemplate->nOut);
 #if WHERETRACE_ENABLED /* 0x8 */
-    if( sqlite3WhereTrace & 0x8 ){
-      sqlite3DebugPrintf(x?"   or-%d:  ":"   or-X:  ", n);
-      whereLoopPrint(pTemplate, pBuilder->pWC);
+      if( sqlite3WhereTrace & 0x8 ){
+        sqlite3DebugPrintf(x?"   or-%d:  ":"   or-X:  ", n);
+        whereLoopPrint(pTemplate, pBuilder->pWC);
+      }
+#endif
     }
-#endif
     return SQLITE_OK;
   }
 
   /* Look for an existing WhereLoop to replace with pTemplate
   */
   whereLoopAdjustCost(pWInfo->pLoops, pTemplate);
   ppPrev = whereLoopFindLesser(&pWInfo->pLoops, pTemplate);
 
   if( ppPrev==0 ){
     /* There already exists a WhereLoop on the list that is better
@@ skipping 57 matching lines @@
       p->u.btree.pIndex = 0;
     }
   }
   return SQLITE_OK;
 }
 
 /*
 ** Adjust the WhereLoop.nOut value downward to account for terms of the
 ** WHERE clause that reference the loop but which are not used by an
 ** index.
+*
+** For every WHERE clause term that is not used by the index
+** and which has a truth probability assigned by one of the likelihood(),
+** likely(), or unlikely() SQL functions, reduce the estimated number
+** of output rows by the probability specified.
 **
-** In the current implementation, the first extra WHERE clause term reduces
-** the number of output rows by a factor of 10 and each additional term
-** reduces the number of output rows by sqrt(2).
+** TUNING:  For every WHERE clause term that is not used by the index
+** and which does not have an assigned truth probability, heuristics
+** described below are used to try to estimate the truth probability.
+** TODO --> Perhaps this is something that could be improved by better
+** table statistics.
+**
+** Heuristic 1:  Estimate the truth probability as 93.75%.  The 93.75%
+** value corresponds to -1 in LogEst notation, so this means decrement
+** the WhereLoop.nOut field for every such WHERE clause term.
+**
+** Heuristic 2:  If there exists one or more WHERE clause terms of the
+** form "x==EXPR" and EXPR is not a constant 0 or 1, then make sure the
+** final output row estimate is no greater than 1/4 of the total number
+** of rows in the table.  In other words, assume that x==EXPR will filter
+** out at least 3 out of 4 rows.  If EXPR is -1 or 0 or 1, then maybe the
+** "x" column is boolean or else -1 or 0 or 1 is a common default value
+** on the "x" column and so in that case only cap the output row estimate
+** at 1/2 instead of 1/4.
 */
 static void whereLoopOutputAdjust(
   WhereClause *pWC,      /* The WHERE clause */
   WhereLoop *pLoop,      /* The loop to adjust downward */
   LogEst nRow            /* Number of rows in the entire table */
 ){
   WhereTerm *pTerm, *pX;
   Bitmask notAllowed = ~(pLoop->prereq|pLoop->maskSelf);
-  int i, j;
-  int nEq = 0;    /* Number of = constraints not within likely()/unlikely() */
+  int i, j, k;
+  LogEst iReduce = 0;    /* pLoop->nOut should not exceed nRow-iReduce */
 
+  assert( (pLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
   for(i=pWC->nTerm, pTerm=pWC->a; i>0; i--, pTerm++){
     if( (pTerm->wtFlags & TERM_VIRTUAL)!=0 ) break;
     if( (pTerm->prereqAll & pLoop->maskSelf)==0 ) continue;
     if( (pTerm->prereqAll & notAllowed)!=0 ) continue;
     for(j=pLoop->nLTerm-1; j>=0; j--){
       pX = pLoop->aLTerm[j];
       if( pX==0 ) continue;
       if( pX==pTerm ) break;
       if( pX->iParent>=0 && (&pWC->a[pX->iParent])==pTerm ) break;
     }
     if( j<0 ){
       if( pTerm->truthProb<=0 ){
+        /* If a truth probability is specified using the likelihood() hints,
+        ** then use the probability provided by the application. */
         pLoop->nOut += pTerm->truthProb;
       }else{
+        /* In the absence of explicit truth probabilities, use heuristics to
+        ** guess a reasonable truth probability. */
         pLoop->nOut--;
-        if( pTerm->eOperator&WO_EQ ) nEq++;
+        if( pTerm->eOperator&(WO_EQ|WO_IS) ){
+          Expr *pRight = pTerm->pExpr->pRight;
+          testcase( pTerm->pExpr->op==TK_IS );
+          if( sqlite3ExprIsInteger(pRight, &k) && k>=(-1) && k<=1 ){
+            k = 10;
+          }else{
+            k = 20;
+          }
+          if( iReduce<k ) iReduce = k;
+        }
       }
     }
   }
-  /* TUNING:  If there is at least one equality constraint in the WHERE
-  ** clause that does not have a likelihood() explicitly assigned to it
-  ** then do not let the estimated number of output rows exceed half 
-  ** the number of rows in the table. */
-  if( nEq && pLoop->nOut>nRow-10 ){
-    pLoop->nOut = nRow - 10;
-  }
+  if( pLoop->nOut > nRow-iReduce )  pLoop->nOut = nRow - iReduce;
 }
 
 /*
 ** Adjust the cost C by the costMult facter T.  This only occurs if
 ** compiled with -DSQLITE_ENABLE_COSTMULT
 */
 #ifdef SQLITE_ENABLE_COSTMULT
 # define ApplyCostMultiplier(C,T)  C += T
 #else
 # define ApplyCostMultiplier(C,T)
@@ skipping 20 matching lines @@
   WhereInfo *pWInfo = pBuilder->pWInfo;  /* WHERE analyse context */
   Parse *pParse = pWInfo->pParse;        /* Parsing context */
   sqlite3 *db = pParse->db;       /* Database connection malloc context */
   WhereLoop *pNew;                /* Template WhereLoop under construction */
   WhereTerm *pTerm;               /* A WhereTerm under consideration */
   int opMask;                     /* Valid operators for constraints */
   WhereScan scan;                 /* Iterator for WHERE terms */
   Bitmask saved_prereq;           /* Original value of pNew->prereq */
   u16 saved_nLTerm;               /* Original value of pNew->nLTerm */
   u16 saved_nEq;                  /* Original value of pNew->u.btree.nEq */
-  u16 saved_nSkip;                /* Original value of pNew->u.btree.nSkip */
+  u16 saved_nSkip;                /* Original value of pNew->nSkip */
   u32 saved_wsFlags;              /* Original value of pNew->wsFlags */
   LogEst saved_nOut;              /* Original value of pNew->nOut */
-  int iCol;                       /* Index of the column in the table */
   int rc = SQLITE_OK;             /* Return code */
   LogEst rSize;                   /* Number of rows in the table */
   LogEst rLogSize;                /* Logarithm of table size */
   WhereTerm *pTop = 0, *pBtm = 0; /* Top and bottom range constraints */
 
   pNew = pBuilder->pNew;
   if( db->mallocFailed ) return SQLITE_NOMEM;
 
   assert( (pNew->wsFlags & WHERE_VIRTUALTABLE)==0 );
   assert( (pNew->wsFlags & WHERE_TOP_LIMIT)==0 );
   if( pNew->wsFlags & WHERE_BTM_LIMIT ){
     opMask = WO_LT|WO_LE;
-  }else if( pProbe->tnum<=0 || (pSrc->jointype & JT_LEFT)!=0 ){
+  }else if( /*pProbe->tnum<=0 ||*/ (pSrc->fg.jointype & JT_LEFT)!=0 ){
     opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE;
   }else{
-    opMask = WO_EQ|WO_IN|WO_ISNULL|WO_GT|WO_GE|WO_LT|WO_LE;
+    opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE|WO_ISNULL|WO_IS;
   }
   if( pProbe->bUnordered ) opMask &= ~(WO_GT|WO_GE|WO_LT|WO_LE);
 
   assert( pNew->u.btree.nEq<pProbe->nColumn );
-  iCol = pProbe->aiColumn[pNew->u.btree.nEq];
 
-  pTerm = whereScanInit(&scan, pBuilder->pWC, pSrc->iCursor, iCol,
-                        opMask, pProbe);
   saved_nEq = pNew->u.btree.nEq;
-  saved_nSkip = pNew->u.btree.nSkip;
+  saved_nSkip = pNew->nSkip;
   saved_nLTerm = pNew->nLTerm;
   saved_wsFlags = pNew->wsFlags;
   saved_prereq = pNew->prereq;
   saved_nOut = pNew->nOut;
+  pTerm = whereScanInit(&scan, pBuilder->pWC, pSrc->iCursor, saved_nEq,
+                        opMask, pProbe);
   pNew->rSetup = 0;
   rSize = pProbe->aiRowLogEst[0];
   rLogSize = estLog(rSize);
-
-  /* Consider using a skip-scan if there are no WHERE clause constraints
-  ** available for the left-most terms of the index, and if the average
-  ** number of repeats in the left-most terms is at least 18. 
-  **
-  ** The magic number 18 is selected on the basis that scanning 17 rows
-  ** is almost always quicker than an index seek (even though if the index
-  ** contains fewer than 2^17 rows we assume otherwise in other parts of
-  ** the code). And, even if it is not, it should not be too much slower. 
-  ** On the other hand, the extra seeks could end up being significantly
-  ** more expensive.  */
-  assert( 42==sqlite3LogEst(18) );
-  if( saved_nEq==saved_nSkip
-   && saved_nEq+1<pProbe->nKeyCol
-   && pProbe->aiRowLogEst[saved_nEq+1]>=42  /* TUNING: Minimum for skip-scan */
-   && (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
-  ){
-    LogEst nIter;
-    pNew->u.btree.nEq++;
-    pNew->u.btree.nSkip++;
-    pNew->aLTerm[pNew->nLTerm++] = 0;
-    pNew->wsFlags |= WHERE_SKIPSCAN;
-    nIter = pProbe->aiRowLogEst[saved_nEq] - pProbe->aiRowLogEst[saved_nEq+1];
-    if( pTerm ){
-      /* TUNING:  When estimating skip-scan for a term that is also indexable,
-      ** multiply the cost of the skip-scan by 2.0, to make it a little less
-      ** desirable than the regular index lookup. */
-      nIter += 10;  assert( 10==sqlite3LogEst(2) );
-    }
-    pNew->nOut -= nIter;
-    /* TUNING:  Because uncertainties in the estimates for skip-scan queries,
-    ** add a 1.375 fudge factor to make skip-scan slightly less likely. */
-    nIter += 5;
-    whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nIter + nInMul);
-    pNew->nOut = saved_nOut;
-    pNew->u.btree.nEq = saved_nEq;
-    pNew->u.btree.nSkip = saved_nSkip;
-  }
   for(; rc==SQLITE_OK && pTerm!=0; pTerm = whereScanNext(&scan)){
     u16 eOp = pTerm->eOperator;   /* Shorthand for pTerm->eOperator */
     LogEst rCostIdx;
     LogEst nOutUnadjusted;        /* nOut before IN() and WHERE adjustments */
     int nIn = 0;
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
     int nRecValid = pBuilder->nRecValid;
 #endif
     if( (eOp==WO_ISNULL || (pTerm->wtFlags&TERM_VNULL)!=0)
-     && (iCol<0 || pSrc->pTab->aCol[iCol].notNull)
+     && indexColumnNotNull(pProbe, saved_nEq)
     ){
       continue; /* ignore IS [NOT] NULL constraints on NOT NULL columns */
     }
     if( pTerm->prereqRight & pNew->maskSelf ) continue;
 
+    /* Do not allow the upper bound of a LIKE optimization range constraint
+    ** to mix with a lower range bound from some other source */
+    if( pTerm->wtFlags & TERM_LIKEOPT && pTerm->eOperator==WO_LT ) continue;
+
     pNew->wsFlags = saved_wsFlags;
     pNew->u.btree.nEq = saved_nEq;
     pNew->nLTerm = saved_nLTerm;
     if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
     pNew->aLTerm[pNew->nLTerm++] = pTerm;
     pNew->prereq = (saved_prereq | pTerm->prereqRight) & ~pNew->maskSelf;
 
     assert( nInMul==0
         || (pNew->wsFlags & WHERE_COLUMN_NULL)!=0 
         || (pNew->wsFlags & WHERE_COLUMN_IN)!=0 
         || (pNew->wsFlags & WHERE_SKIPSCAN)!=0 
     );
 
     if( eOp & WO_IN ){
       Expr *pExpr = pTerm->pExpr;
       pNew->wsFlags |= WHERE_COLUMN_IN;
       if( ExprHasProperty(pExpr, EP_xIsSelect) ){
         /* "x IN (SELECT ...)":  TUNING: the SELECT returns 25 rows */
         nIn = 46;  assert( 46==sqlite3LogEst(25) );
       }else if( ALWAYS(pExpr->x.pList && pExpr->x.pList->nExpr) ){
         /* "x IN (value, value, ...)" */
         nIn = sqlite3LogEst(pExpr->x.pList->nExpr);
       }
       assert( nIn>0 );  /* RHS always has 2 or more terms...  The parser
                         ** changes "x IN (?)" into "x=?". */
 
-    }else if( eOp & (WO_EQ) ){
+    }else if( eOp & (WO_EQ|WO_IS) ){
+      int iCol = pProbe->aiColumn[saved_nEq];
       pNew->wsFlags |= WHERE_COLUMN_EQ;
-      if( iCol<0 || (nInMul==0 && pNew->u.btree.nEq==pProbe->nKeyCol-1) ){
-        if( iCol>=0 && !IsUniqueIndex(pProbe) ){
+      assert( saved_nEq==pNew->u.btree.nEq );
+      if( iCol==XN_ROWID 
+       || (iCol>0 && nInMul==0 && saved_nEq==pProbe->nKeyCol-1)
+      ){
+        if( iCol>=0 && pProbe->uniqNotNull==0 ){
           pNew->wsFlags |= WHERE_UNQ_WANTED;
         }else{
           pNew->wsFlags |= WHERE_ONEROW;
         }
       }
     }else if( eOp & WO_ISNULL ){
       pNew->wsFlags |= WHERE_COLUMN_NULL;
     }else if( eOp & (WO_GT|WO_GE) ){
       testcase( eOp & WO_GT );
       testcase( eOp & WO_GE );
       pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_BTM_LIMIT;
       pBtm = pTerm;
       pTop = 0;
+      if( pTerm->wtFlags & TERM_LIKEOPT ){
+        /* Range contraints that come from the LIKE optimization are
+        ** always used in pairs. */
+        pTop = &pTerm[1];
+        assert( (pTop-(pTerm->pWC->a))<pTerm->pWC->nTerm );
+        assert( pTop->wtFlags & TERM_LIKEOPT );
+        assert( pTop->eOperator==WO_LT );
+        if( whereLoopResize(db, pNew, pNew->nLTerm+1) ) break; /* OOM */
+        pNew->aLTerm[pNew->nLTerm++] = pTop;
+        pNew->wsFlags |= WHERE_TOP_LIMIT;
+      }
     }else{
       assert( eOp & (WO_LT|WO_LE) );
       testcase( eOp & WO_LT );
       testcase( eOp & WO_LE );
       pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_TOP_LIMIT;
       pTop = pTerm;
       pBtm = (pNew->wsFlags & WHERE_BTM_LIMIT)!=0 ?
                      pNew->aLTerm[pNew->nLTerm-2] : 0;
     }
 
     /* At this point pNew->nOut is set to the number of rows expected to
     ** be visited by the index scan before considering term pTerm, or the
     ** values of nIn and nInMul. In other words, assuming that all 
     ** "x IN(...)" terms are replaced with "x = ?". This block updates
     ** the value of pNew->nOut to account for pTerm (but not nIn/nInMul).  */
     assert( pNew->nOut==saved_nOut );
     if( pNew->wsFlags & WHERE_COLUMN_RANGE ){
       /* Adjust nOut using stat3/stat4 data. Or, if there is no stat3/stat4
       ** data, using some other estimate.  */
       whereRangeScanEst(pParse, pBuilder, pBtm, pTop, pNew);
     }else{
       int nEq = ++pNew->u.btree.nEq;
-      assert( eOp & (WO_ISNULL|WO_EQ|WO_IN) );
+      assert( eOp & (WO_ISNULL|WO_EQ|WO_IN|WO_IS) );
 
       assert( pNew->nOut==saved_nOut );
-      if( pTerm->truthProb<=0 && iCol>=0 ){
+      if( pTerm->truthProb<=0 && pProbe->aiColumn[saved_nEq]>=0 ){
         assert( (eOp & WO_IN) || nIn==0 );
         testcase( eOp & WO_IN );
         pNew->nOut += pTerm->truthProb;
         pNew->nOut -= nIn;
       }else{
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
         tRowcnt nOut = 0;
         if( nInMul==0 
          && pProbe->nSample 
          && pNew->u.btree.nEq<=pProbe->nSampleCol
-         && OptimizationEnabled(db, SQLITE_Stat3) 
          && ((eOp & WO_IN)==0 || !ExprHasProperty(pTerm->pExpr, EP_xIsSelect))
         ){
           Expr *pExpr = pTerm->pExpr;
-          if( (eOp & (WO_EQ|WO_ISNULL))!=0 ){
+          if( (eOp & (WO_EQ|WO_ISNULL|WO_IS))!=0 ){
             testcase( eOp & WO_EQ );
+            testcase( eOp & WO_IS );
             testcase( eOp & WO_ISNULL );
             rc = whereEqualScanEst(pParse, pBuilder, pExpr->pRight, &nOut);
           }else{
             rc = whereInScanEst(pParse, pBuilder, pExpr->x.pList, &nOut);
           }
           if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
           if( rc!=SQLITE_OK ) break;          /* Jump out of the pTerm loop */
           if( nOut ){
             pNew->nOut = sqlite3LogEst(nOut);
             if( pNew->nOut>saved_nOut ) pNew->nOut = saved_nOut;
@@ skipping 42 matching lines @@
     ){
       whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nInMul+nIn);
     }
     pNew->nOut = saved_nOut;
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
     pBuilder->nRecValid = nRecValid;
 #endif
   }
   pNew->prereq = saved_prereq;
   pNew->u.btree.nEq = saved_nEq;
-  pNew->u.btree.nSkip = saved_nSkip;
+  pNew->nSkip = saved_nSkip;
   pNew->wsFlags = saved_wsFlags;
   pNew->nOut = saved_nOut;
   pNew->nLTerm = saved_nLTerm;
+
+  /* Consider using a skip-scan if there are no WHERE clause constraints
+  ** available for the left-most terms of the index, and if the average
+  ** number of repeats in the left-most terms is at least 18. 
+  **
+  ** The magic number 18 is selected on the basis that scanning 17 rows
+  ** is almost always quicker than an index seek (even though if the index
+  ** contains fewer than 2^17 rows we assume otherwise in other parts of
+  ** the code). And, even if it is not, it should not be too much slower. 
+  ** On the other hand, the extra seeks could end up being significantly
+  ** more expensive.  */
+  assert( 42==sqlite3LogEst(18) );
+  if( saved_nEq==saved_nSkip
+   && saved_nEq+1<pProbe->nKeyCol
+   && pProbe->noSkipScan==0
+   && pProbe->aiRowLogEst[saved_nEq+1]>=42  /* TUNING: Minimum for skip-scan */
+   && (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
+  ){
+    LogEst nIter;
+    pNew->u.btree.nEq++;
+    pNew->nSkip++;
+    pNew->aLTerm[pNew->nLTerm++] = 0;
+    pNew->wsFlags |= WHERE_SKIPSCAN;
+    nIter = pProbe->aiRowLogEst[saved_nEq] - pProbe->aiRowLogEst[saved_nEq+1];
+    pNew->nOut -= nIter;
+    /* TUNING:  Because uncertainties in the estimates for skip-scan queries,
+    ** add a 1.375 fudge factor to make skip-scan slightly less likely. */
+    nIter += 5;
+    whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nIter + nInMul);
+    pNew->nOut = saved_nOut;
+    pNew->u.btree.nEq = saved_nEq;
+    pNew->nSkip = saved_nSkip;
+    pNew->wsFlags = saved_wsFlags;
+  }
+
   return rc;
 }
 
 /*
 ** Return True if it is possible that pIndex might be useful in
 ** implementing the ORDER BY clause in pBuilder.
 **
 ** Return False if pBuilder does not contain an ORDER BY clause or
 ** if there is no way for pIndex to be useful in implementing that
 ** ORDER BY clause.
 */
 static int indexMightHelpWithOrderBy(
   WhereLoopBuilder *pBuilder,
   Index *pIndex,
   int iCursor
 ){
   ExprList *pOB;
+  ExprList *aColExpr;
   int ii, jj;
 
   if( pIndex->bUnordered ) return 0;
   if( (pOB = pBuilder->pWInfo->pOrderBy)==0 ) return 0;
   for(ii=0; ii<pOB->nExpr; ii++){
     Expr *pExpr = sqlite3ExprSkipCollate(pOB->a[ii].pExpr);
-    if( pExpr->op!=TK_COLUMN ) return 0;
-    if( pExpr->iTable==iCursor ){
+    if( pExpr->op==TK_COLUMN && pExpr->iTable==iCursor ){
       if( pExpr->iColumn<0 ) return 1;
       for(jj=0; jj<pIndex->nKeyCol; jj++){
         if( pExpr->iColumn==pIndex->aiColumn[jj] ) return 1;
       }
+    }else if( (aColExpr = pIndex->aColExpr)!=0 ){
+      for(jj=0; jj<pIndex->nKeyCol; jj++){
+        if( pIndex->aiColumn[jj]!=XN_EXPR ) continue;
+        if( sqlite3ExprCompare(pExpr,aColExpr->a[jj].pExpr,iCursor)==0 ){
+          return 1;
+        }
+      }
     }
   }
   return 0;
 }
 
 /*
 ** Return a bitmask where 1s indicate that the corresponding column of
 ** the table is used by an index.  Only the first 63 columns are considered.
 */
 static Bitmask columnsInIndex(Index *pIdx){
   Bitmask m = 0;
   int j;
   for(j=pIdx->nColumn-1; j>=0; j--){
     int x = pIdx->aiColumn[j];
     if( x>=0 ){
       testcase( x==BMS-1 );
       testcase( x==BMS-2 );
       if( x<BMS-1 ) m |= MASKBIT(x);
     }
   }
   return m;
 }
 
 /* Check to see if a partial index with pPartIndexWhere can be used
 ** in the current query.  Return true if it can be and false if not.
 */
 static int whereUsablePartialIndex(int iTab, WhereClause *pWC, Expr *pWhere){
   int i;
   WhereTerm *pTerm;
+  while( pWhere->op==TK_AND ){
+    if( !whereUsablePartialIndex(iTab,pWC,pWhere->pLeft) ) return 0;
+    pWhere = pWhere->pRight;
+  }
   for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
-    if( sqlite3ExprImpliesExpr(pTerm->pExpr, pWhere, iTab) ) return 1;
+    Expr *pExpr = pTerm->pExpr;
+    if( sqlite3ExprImpliesExpr(pExpr, pWhere, iTab) 
+     && (!ExprHasProperty(pExpr, EP_FromJoin) || pExpr->iRightJoinTable==iTab)
+    ){
+      return 1;
+    }
   }
   return 0;
 }
 
 /*
 ** Add all WhereLoop objects for a single table of the join where the table
 ** is idenfied by pBuilder->pNew->iTab.  That table is guaranteed to be
 ** a b-tree table, not a virtual table.
 **
 ** The costs (WhereLoop.rRun) of the b-tree loops added by this function
@@ skipping 48 matching lines @@
   Table *pTab;                /* Table being queried */
   
   pNew = pBuilder->pNew;
   pWInfo = pBuilder->pWInfo;
   pTabList = pWInfo->pTabList;
   pSrc = pTabList->a + pNew->iTab;
   pTab = pSrc->pTab;
   pWC = pBuilder->pWC;
   assert( !IsVirtual(pSrc->pTab) );
 
-  if( pSrc->pIndex ){
+  if( pSrc->pIBIndex ){
     /* An INDEXED BY clause specifies a particular index to use */
-    pProbe = pSrc->pIndex;
+    pProbe = pSrc->pIBIndex;
   }else if( !HasRowid(pTab) ){
     pProbe = pTab->pIndex;
   }else{
     /* There is no INDEXED BY clause.  Create a fake Index object in local
     ** variable sPk to represent the rowid primary key index.  Make this
     ** fake index the first in a chain of Index objects with all of the real
     ** indices to follow */
     Index *pFirst;                  /* First of real indices on the table */
     memset(&sPk, 0, sizeof(Index));
     sPk.nKeyCol = 1;
     sPk.nColumn = 1;
     sPk.aiColumn = &aiColumnPk;
     sPk.aiRowLogEst = aiRowEstPk;
     sPk.onError = OE_Replace;
     sPk.pTable = pTab;
     sPk.szIdxRow = pTab->szTabRow;
     aiRowEstPk[0] = pTab->nRowLogEst;
     aiRowEstPk[1] = 0;
     pFirst = pSrc->pTab->pIndex;
-    if( pSrc->notIndexed==0 ){
+    if( pSrc->fg.notIndexed==0 ){
       /* The real indices of the table are only considered if the
       ** NOT INDEXED qualifier is omitted from the FROM clause */
       sPk.pNext = pFirst;
     }
     pProbe = &sPk;
   }
   rSize = pTab->nRowLogEst;
   rLogSize = estLog(rSize);
 
 #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
   /* Automatic indexes */
-  if( !pBuilder->pOrSet
+  if( !pBuilder->pOrSet      /* Not part of an OR optimization */
+   && (pWInfo->wctrlFlags & WHERE_NO_AUTOINDEX)==0
    && (pWInfo->pParse->db->flags & SQLITE_AutoIndex)!=0
-   && pSrc->pIndex==0
-   && !pSrc->viaCoroutine
-   && !pSrc->notIndexed
-   && HasRowid(pTab)
-   && !pSrc->isCorrelated
-   && !pSrc->isRecursive
+   && pSrc->pIBIndex==0      /* Has no INDEXED BY clause */
+   && !pSrc->fg.notIndexed   /* Has no NOT INDEXED clause */
+   && HasRowid(pTab)         /* Not WITHOUT ROWID table. (FIXME: Why not?) */
+   && !pSrc->fg.isCorrelated /* Not a correlated subquery */
+   && !pSrc->fg.isRecursive  /* Not a recursive common table expression. */
   ){
     /* Generate auto-index WhereLoops */
     WhereTerm *pTerm;
     WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
     for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
       if( pTerm->prereqRight & pNew->maskSelf ) continue;
       if( termCanDriveIndex(pTerm, pSrc, 0) ){
         pNew->u.btree.nEq = 1;
-        pNew->u.btree.nSkip = 0;
+        pNew->nSkip = 0;
         pNew->u.btree.pIndex = 0;
         pNew->nLTerm = 1;
         pNew->aLTerm[0] = pTerm;
         /* TUNING: One-time cost for computing the automatic index is
         ** estimated to be X*N*log2(N) where N is the number of rows in
         ** the table being indexed and where X is 7 (LogEst=28) for normal
         ** tables or 1.375 (LogEst=4) for views and subqueries.  The value
         ** of X is smaller for views and subqueries so that the query planner
         ** will be more aggressive about generating automatic indexes for
         ** those objects, since there is no opportunity to add schema
@@ skipping 20 matching lines @@
   /* Loop over all indices
   */
   for(; rc==SQLITE_OK && pProbe; pProbe=pProbe->pNext, iSortIdx++){
     if( pProbe->pPartIdxWhere!=0
      && !whereUsablePartialIndex(pSrc->iCursor, pWC, pProbe->pPartIdxWhere) ){
       testcase( pNew->iTab!=pSrc->iCursor );  /* See ticket [98d973b8f5] */
       continue;  /* Partial index inappropriate for this query */
     }
     rSize = pProbe->aiRowLogEst[0];
     pNew->u.btree.nEq = 0;
-    pNew->u.btree.nSkip = 0;
+    pNew->nSkip = 0;
     pNew->nLTerm = 0;
     pNew->iSortIdx = 0;
     pNew->rSetup = 0;
     pNew->prereq = mExtra;
     pNew->nOut = rSize;
     pNew->u.btree.pIndex = pProbe;
     b = indexMightHelpWithOrderBy(pBuilder, pProbe, pSrc->iCursor);
     /* The ONEPASS_DESIRED flags never occurs together with ORDER BY */
     assert( (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || b==0 );
     if( pProbe->tnum<=0 ){
@@ skipping 50 matching lines @@
 
     rc = whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, 0);
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
     sqlite3Stat4ProbeFree(pBuilder->pRec);
     pBuilder->nRecValid = 0;
     pBuilder->pRec = 0;
 #endif
 
     /* If there was an INDEXED BY clause, then only that one index is
     ** considered. */
-    if( pSrc->pIndex ) break;
+    if( pSrc->pIBIndex ) break;
   }
   return rc;
 }
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
 /*
 ** Add all WhereLoop objects for a table of the join identified by
 ** pBuilder->pNew->iTab.  That table is guaranteed to be a virtual table.
+**
+** If there are no LEFT or CROSS JOIN joins in the query, both mExtra and
+** mUnusable are set to 0. Otherwise, mExtra is a mask of all FROM clause
+** entries that occur before the virtual table in the FROM clause and are
+** separated from it by at least one LEFT or CROSS JOIN. Similarly, the
+** mUnusable mask contains all FROM clause entries that occur after the
+** virtual table and are separated from it by at least one LEFT or 
+** CROSS JOIN. 
+**
+** For example, if the query were:
+**
+**   ... FROM t1, t2 LEFT JOIN t3, t4, vt CROSS JOIN t5, t6;
+**
+** then mExtra corresponds to (t1, t2) and mUnusable to (t5, t6).
+**
+** All the tables in mExtra must be scanned before the current virtual 
+** table. So any terms for which all prerequisites are satisfied by 
+** mExtra may be specified as "usable" in all calls to xBestIndex. 
+** Conversely, all tables in mUnusable must be scanned after the current
+** virtual table, so any terms for which the prerequisites overlap with
+** mUnusable should always be configured as "not-usable" for xBestIndex.
 */
 static int whereLoopAddVirtual(
   WhereLoopBuilder *pBuilder,  /* WHERE clause information */
-  Bitmask mExtra
+  Bitmask mExtra,              /* Tables that must be scanned before this one */
+  Bitmask mUnusable            /* Tables that must be scanned after this one */
 ){
   WhereInfo *pWInfo;           /* WHERE analysis context */
   Parse *pParse;               /* The parsing context */
   WhereClause *pWC;            /* The WHERE clause */
   struct SrcList_item *pSrc;   /* The FROM clause term to search */
   Table *pTab;
   sqlite3 *db;
   sqlite3_index_info *pIdxInfo;
   struct sqlite3_index_constraint *pIdxCons;
   struct sqlite3_index_constraint_usage *pUsage;
   WhereTerm *pTerm;
   int i, j;
   int iTerm, mxTerm;
   int nConstraint;
   int seenIn = 0;              /* True if an IN operator is seen */
   int seenVar = 0;             /* True if a non-constant constraint is seen */
   int iPhase;                  /* 0: const w/o IN, 1: const, 2: no IN,  2: IN */
   WhereLoop *pNew;
   int rc = SQLITE_OK;
 
+  assert( (mExtra & mUnusable)==0 );
   pWInfo = pBuilder->pWInfo;
   pParse = pWInfo->pParse;
   db = pParse->db;
   pWC = pBuilder->pWC;
   pNew = pBuilder->pNew;
   pSrc = &pWInfo->pTabList->a[pNew->iTab];
   pTab = pSrc->pTab;
   assert( IsVirtual(pTab) );
-  pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pBuilder->pOrderBy);
+  pIdxInfo = allocateIndexInfo(pParse, pWC, mUnusable, pSrc,pBuilder->pOrderBy);
   if( pIdxInfo==0 ) return SQLITE_NOMEM;
   pNew->prereq = 0;
   pNew->rSetup = 0;
   pNew->wsFlags = WHERE_VIRTUALTABLE;
   pNew->nLTerm = 0;
   pNew->u.vtab.needFree = 0;
   pUsage = pIdxInfo->aConstraintUsage;
   nConstraint = pIdxInfo->nConstraint;
   if( whereLoopResize(db, pNew, nConstraint) ){
     sqlite3DbFree(db, pIdxInfo);
     return SQLITE_NOMEM;
   }
 
   for(iPhase=0; iPhase<=3; iPhase++){
     if( !seenIn && (iPhase&1)!=0 ){
       iPhase++;
       if( iPhase>3 ) break;
     }
     if( !seenVar && iPhase>1 ) break;
     pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
     for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
       j = pIdxCons->iTermOffset;
       pTerm = &pWC->a[j];
       switch( iPhase ){
         case 0:    /* Constants without IN operator */
           pIdxCons->usable = 0;
           if( (pTerm->eOperator & WO_IN)!=0 ){
             seenIn = 1;
           }
-          if( pTerm->prereqRight!=0 ){
+          if( (pTerm->prereqRight & ~mExtra)!=0 ){
             seenVar = 1;
           }else if( (pTerm->eOperator & WO_IN)==0 ){
             pIdxCons->usable = 1;
           }
           break;
         case 1:    /* Constants with IN operators */
           assert( seenIn );
-          pIdxCons->usable = (pTerm->prereqRight==0);
+          pIdxCons->usable = (pTerm->prereqRight & ~mExtra)==0;
           break;
         case 2:    /* Variables without IN */
           assert( seenVar );
           pIdxCons->usable = (pTerm->eOperator & WO_IN)==0;
           break;
         default:   /* Variables with IN */
           assert( seenVar && seenIn );
           pIdxCons->usable = 1;
           break;
       }
     }
     memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
     if( pIdxInfo->needToFreeIdxStr ) sqlite3_free(pIdxInfo->idxStr);
     pIdxInfo->idxStr = 0;
     pIdxInfo->idxNum = 0;
     pIdxInfo->needToFreeIdxStr = 0;
     pIdxInfo->orderByConsumed = 0;
     pIdxInfo->estimatedCost = SQLITE_BIG_DBL / (double)2;
     pIdxInfo->estimatedRows = 25;
+    pIdxInfo->idxFlags = 0;
+    pIdxInfo->colUsed = (sqlite3_int64)pSrc->colUsed;
     rc = vtabBestIndex(pParse, pTab, pIdxInfo);
     if( rc ) goto whereLoopAddVtab_exit;
     pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
     pNew->prereq = mExtra;
     mxTerm = -1;
     assert( pNew->nLSlot>=nConstraint );
     for(i=0; i<nConstraint; i++) pNew->aLTerm[i] = 0;
     pNew->u.vtab.omitMask = 0;
     for(i=0; i<nConstraint; i++, pIdxCons++){
       if( (iTerm = pUsage[i].argvIndex - 1)>=0 ){
@@ skipping 25 matching lines @@
             ** If we do attempt to use such a constraint, some rows might be
             ** repeated in the output. */
             break;
           }
           /* A virtual table that is constrained by an IN clause may not
           ** consume the ORDER BY clause because (1) the order of IN terms
           ** is not necessarily related to the order of output terms and
           ** (2) Multiple outputs from a single IN value will not merge
           ** together.  */
           pIdxInfo->orderByConsumed = 0;
+          pIdxInfo->idxFlags &= ~SQLITE_INDEX_SCAN_UNIQUE;
         }
       }
     }
     if( i>=nConstraint ){
       pNew->nLTerm = mxTerm+1;
       assert( pNew->nLTerm<=pNew->nLSlot );
       pNew->u.vtab.idxNum = pIdxInfo->idxNum;
       pNew->u.vtab.needFree = pIdxInfo->needToFreeIdxStr;
       pIdxInfo->needToFreeIdxStr = 0;
       pNew->u.vtab.idxStr = pIdxInfo->idxStr;
       pNew->u.vtab.isOrdered = (i8)(pIdxInfo->orderByConsumed ?
                                       pIdxInfo->nOrderBy : 0);
       pNew->rSetup = 0;
       pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
       pNew->nOut = sqlite3LogEst(pIdxInfo->estimatedRows);
+
+      /* Set the WHERE_ONEROW flag if the xBestIndex() method indicated
+      ** that the scan will visit at most one row. Clear it otherwise. */
+      if( pIdxInfo->idxFlags & SQLITE_INDEX_SCAN_UNIQUE ){
+        pNew->wsFlags |= WHERE_ONEROW;
+      }else{
+        pNew->wsFlags &= ~WHERE_ONEROW;
+      }
       whereLoopInsert(pBuilder, pNew);
       if( pNew->u.vtab.needFree ){
         sqlite3_free(pNew->u.vtab.idxStr);
         pNew->u.vtab.needFree = 0;
       }
     }
   }  
 
 whereLoopAddVtab_exit:
   if( pIdxInfo->needToFreeIdxStr ) sqlite3_free(pIdxInfo->idxStr);
   sqlite3DbFree(db, pIdxInfo);
   return rc;
 }
 #endif /* SQLITE_OMIT_VIRTUALTABLE */
 
 /*
 ** Add WhereLoop entries to handle OR terms.  This works for either
 ** btrees or virtual tables.
 */
-static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
+static int whereLoopAddOr(
+  WhereLoopBuilder *pBuilder, 
+  Bitmask mExtra, 
+  Bitmask mUnusable
+){
   WhereInfo *pWInfo = pBuilder->pWInfo;
   WhereClause *pWC;
   WhereLoop *pNew;
   WhereTerm *pTerm, *pWCEnd;
   int rc = SQLITE_OK;
   int iCur;
   WhereClause tempWC;
   WhereLoopBuilder sSubBuild;
   WhereOrSet sSum, sCur;
   struct SrcList_item *pItem;
@@ skipping 38 matching lines @@
         WHERETRACE(0x200, ("OR-term %d of %p has %d subterms:\n", 
                    (int)(pOrTerm-pOrWC->a), pTerm, sSubBuild.pWC->nTerm));
         if( sqlite3WhereTrace & 0x400 ){
           for(i=0; i<sSubBuild.pWC->nTerm; i++){
             whereTermPrint(&sSubBuild.pWC->a[i], i);
           }
         }
 #endif
 #ifndef SQLITE_OMIT_VIRTUALTABLE
         if( IsVirtual(pItem->pTab) ){
-          rc = whereLoopAddVirtual(&sSubBuild, mExtra);
+          rc = whereLoopAddVirtual(&sSubBuild, mExtra, mUnusable);
         }else
 #endif
         {
           rc = whereLoopAddBtree(&sSubBuild, mExtra);
         }
         if( rc==SQLITE_OK ){
-          rc = whereLoopAddOr(&sSubBuild, mExtra);
+          rc = whereLoopAddOr(&sSubBuild, mExtra, mUnusable);
         }
         assert( rc==SQLITE_OK || sCur.n==0 );
         if( sCur.n==0 ){
           sSum.n = 0;
           break;
         }else if( once ){
           whereOrMove(&sSum, &sCur);
           once = 0;
         }else{
           WhereOrSet sPrev;
@@ skipping 41 matching lines @@
 /*
 ** Add all WhereLoop objects for all tables 
 */
 static int whereLoopAddAll(WhereLoopBuilder *pBuilder){
   WhereInfo *pWInfo = pBuilder->pWInfo;
   Bitmask mExtra = 0;
   Bitmask mPrior = 0;
   int iTab;
   SrcList *pTabList = pWInfo->pTabList;
   struct SrcList_item *pItem;
+  struct SrcList_item *pEnd = &pTabList->a[pWInfo->nLevel];
   sqlite3 *db = pWInfo->pParse->db;
-  int nTabList = pWInfo->nLevel;
   int rc = SQLITE_OK;
-  u8 priorJoinType = 0;
   WhereLoop *pNew;
+  u8 priorJointype = 0;
 
   /* Loop over the tables in the join, from left to right */
   pNew = pBuilder->pNew;
   whereLoopInit(pNew);
-  for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
+  for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
+    Bitmask mUnusable = 0;
     pNew->iTab = iTab;
-    pNew->maskSelf = getMask(&pWInfo->sMaskSet, pItem->iCursor);
-    if( ((pItem->jointype|priorJoinType) & (JT_LEFT|JT_CROSS))!=0 ){
+    pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
+    if( ((pItem->fg.jointype|priorJointype) & (JT_LEFT|JT_CROSS))!=0 ){
+      /* This condition is true when pItem is the FROM clause term on the
+      ** right-hand-side of a LEFT or CROSS JOIN.  */
       mExtra = mPrior;
     }
-    priorJoinType = pItem->jointype;
+    priorJointype = pItem->fg.jointype;
     if( IsVirtual(pItem->pTab) ){
-      rc = whereLoopAddVirtual(pBuilder, mExtra);
+      struct SrcList_item *p;
+      for(p=&pItem[1]; p<pEnd; p++){
+        if( mUnusable || (p->fg.jointype & (JT_LEFT|JT_CROSS)) ){
+          mUnusable |= sqlite3WhereGetMask(&pWInfo->sMaskSet, p->iCursor);
+        }
+      }
+      rc = whereLoopAddVirtual(pBuilder, mExtra, mUnusable);
     }else{
       rc = whereLoopAddBtree(pBuilder, mExtra);
     }
     if( rc==SQLITE_OK ){
-      rc = whereLoopAddOr(pBuilder, mExtra);
+      rc = whereLoopAddOr(pBuilder, mExtra, mUnusable);
     }
     mPrior |= pNew->maskSelf;
     if( rc || db->mallocFailed ) break;
   }
+
   whereLoopClear(db, pNew);
   return rc;
 }
 
 /*
 ** Examine a WherePath (with the addition of the extra WhereLoop of the 5th
 ** parameters) to see if it outputs rows in the requested ORDER BY
 ** (or GROUP BY) without requiring a separate sort operation.  Return N:
 ** 
 **   N>0:   N terms of the ORDER BY clause are satisfied
@@ skipping 85 matching lines @@
     /* Mark off any ORDER BY term X that is a column in the table of
     ** the current loop for which there is term in the WHERE
     ** clause of the form X IS NULL or X=? that reference only outer
     ** loops.
     */
     for(i=0; i<nOrderBy; i++){
       if( MASKBIT(i) & obSat ) continue;
       pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
       if( pOBExpr->op!=TK_COLUMN ) continue;
       if( pOBExpr->iTable!=iCur ) continue;
-      pTerm = findTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
-                       ~ready, WO_EQ|WO_ISNULL, 0);
+      pTerm = sqlite3WhereFindTerm(&pWInfo->sWC, iCur, pOBExpr->iColumn,
+                       ~ready, WO_EQ|WO_ISNULL|WO_IS, 0);
       if( pTerm==0 ) continue;
-      if( (pTerm->eOperator&WO_EQ)!=0 && pOBExpr->iColumn>=0 ){
+      if( (pTerm->eOperator&(WO_EQ|WO_IS))!=0 && pOBExpr->iColumn>=0 ){
         const char *z1, *z2;
         pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
         if( !pColl ) pColl = db->pDfltColl;
         z1 = pColl->zName;
         pColl = sqlite3ExprCollSeq(pWInfo->pParse, pTerm->pExpr);
         if( !pColl ) pColl = db->pDfltColl;
         z2 = pColl->zName;
         if( sqlite3StrICmp(z1, z2)!=0 ) continue;
+        testcase( pTerm->pExpr->op==TK_IS );
       }
       obSat |= MASKBIT(i);
     }
 
     if( (pLoop->wsFlags & WHERE_ONEROW)==0 ){
       if( pLoop->wsFlags & WHERE_IPK ){
         pIndex = 0;
         nKeyCol = 0;
         nColumn = 1;
       }else if( (pIndex = pLoop->u.btree.pIndex)==0 || pIndex->bUnordered ){
         return 0;
       }else{
         nKeyCol = pIndex->nKeyCol;
         nColumn = pIndex->nColumn;
         assert( nColumn==nKeyCol+1 || !HasRowid(pIndex->pTable) );
-        assert( pIndex->aiColumn[nColumn-1]==(-1) || !HasRowid(pIndex->pTable));
+        assert( pIndex->aiColumn[nColumn-1]==XN_ROWID
+                          || !HasRowid(pIndex->pTable));
         isOrderDistinct = IsUniqueIndex(pIndex);
       }
 
       /* Loop through all columns of the index and deal with the ones
       ** that are not constrained by == or IN.
       */
       rev = revSet = 0;
       distinctColumns = 0;
       for(j=0; j<nColumn; j++){
         u8 bOnce;   /* True to run the ORDER BY search loop */
 
         /* Skip over == and IS NULL terms */
         if( j<pLoop->u.btree.nEq
-         && pLoop->u.btree.nSkip==0
-         && ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL))!=0
+         && pLoop->nSkip==0
+         && ((i = pLoop->aLTerm[j]->eOperator) & (WO_EQ|WO_ISNULL|WO_IS))!=0
         ){
           if( i & WO_ISNULL ){
             testcase( isOrderDistinct );
             isOrderDistinct = 0;
           }
           continue;  
         }
 
         /* Get the column number in the table (iColumn) and sort order
         ** (revIdx) for the j-th column of the index.
         */
         if( pIndex ){
           iColumn = pIndex->aiColumn[j];
           revIdx = pIndex->aSortOrder[j];
           if( iColumn==pIndex->pTable->iPKey ) iColumn = -1;
         }else{
-          iColumn = -1;
+          iColumn = XN_ROWID;
           revIdx = 0;
         }
 
         /* An unconstrained column that might be NULL means that this
         ** WhereLoop is not well-ordered
         */
         if( isOrderDistinct
          && iColumn>=0
          && j>=pLoop->u.btree.nEq
          && pIndex->pTable->aCol[iColumn].notNull==0
         ){
           isOrderDistinct = 0;
         }
 
         /* Find the ORDER BY term that corresponds to the j-th column
         ** of the index and mark that ORDER BY term off 
         */
         bOnce = 1;
         isMatch = 0;
         for(i=0; bOnce && i<nOrderBy; i++){
           if( MASKBIT(i) & obSat ) continue;
           pOBExpr = sqlite3ExprSkipCollate(pOrderBy->a[i].pExpr);
           testcase( wctrlFlags & WHERE_GROUPBY );
           testcase( wctrlFlags & WHERE_DISTINCTBY );
           if( (wctrlFlags & (WHERE_GROUPBY|WHERE_DISTINCTBY))==0 ) bOnce = 0;
-          if( pOBExpr->op!=TK_COLUMN ) continue;
-          if( pOBExpr->iTable!=iCur ) continue;
-          if( pOBExpr->iColumn!=iColumn ) continue;
+          if( iColumn>=(-1) ){
+            if( pOBExpr->op!=TK_COLUMN ) continue;
+            if( pOBExpr->iTable!=iCur ) continue;
+            if( pOBExpr->iColumn!=iColumn ) continue;
+          }else{
+            if( sqlite3ExprCompare(pOBExpr,pIndex->aColExpr->a[j].pExpr,iCur) ){
+              continue;
+            }
+          }
           if( iColumn>=0 ){
             pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
             if( !pColl ) pColl = db->pDfltColl;
             if( sqlite3StrICmp(pColl->zName, pIndex->azColl[j])!=0 ) continue;
           }
           isMatch = 1;
           break;
         }
         if( isMatch && (wctrlFlags & WHERE_GROUPBY)==0 ){
           /* Make sure the sort order is compatible in an ORDER BY clause.
@@ skipping 28 matching lines @@
     } /* end-if not one-row */
 
     /* Mark off any other ORDER BY terms that reference pLoop */
     if( isOrderDistinct ){
       orderDistinctMask |= pLoop->maskSelf;
       for(i=0; i<nOrderBy; i++){
         Expr *p;
         Bitmask mTerm;
         if( MASKBIT(i) & obSat ) continue;
         p = pOrderBy->a[i].pExpr;
-        mTerm = exprTableUsage(&pWInfo->sMaskSet,p);
+        mTerm = sqlite3WhereExprUsage(&pWInfo->sMaskSet,p);
         if( mTerm==0 && !sqlite3ExprIsConstant(p) ) continue;
         if( (mTerm&~orderDistinctMask)==0 ){
           obSat |= MASKBIT(i);
         }
       }
     }
   } /* End the loop over all WhereLoops from outer-most down to inner-most */
   if( obSat==obDone ) return (i8)nOrderBy;
   if( !isOrderDistinct ){
     for(i=nOrderBy-1; i>0; i--){
@@ skipping 161 matching lines @@
     ** the ORDER BY clause are already in order, where X is the array 
     ** index.  */
     aSortCost = (LogEst*)pX;
     memset(aSortCost, 0, sizeof(LogEst) * nOrderBy);
   }
   assert( aSortCost==0 || &pSpace[nSpace]==(char*)&aSortCost[nOrderBy] );
   assert( aSortCost!=0 || &pSpace[nSpace]==(char*)pX );
 
   /* Seed the search with a single WherePath containing zero WhereLoops.
   **
-  ** TUNING: Do not let the number of iterations go above 25.  If the cost
-  ** of computing an automatic index is not paid back within the first 25
+  ** TUNING: Do not let the number of iterations go above 28.  If the cost
+  ** of computing an automatic index is not paid back within the first 28
   ** rows, then do not use the automatic index. */
-  aFrom[0].nRow = MIN(pParse->nQueryLoop, 46);  assert( 46==sqlite3LogEst(25) );
+  aFrom[0].nRow = MIN(pParse->nQueryLoop, 48);  assert( 48==sqlite3LogEst(28) );
   nFrom = 1;
   assert( aFrom[0].isOrdered==0 );
   if( nOrderBy ){
     /* If nLoop is zero, then there are no FROM terms in the query. Since
     ** in this case the query may return a maximum of one row, the results
     ** are already in the requested order. Set isOrdered to nOrderBy to
     ** indicate this. Or, if nLoop is greater than zero, set isOrdered to
     ** -1, indicating that the result set may or may not be ordered, 
     ** depending on the loops added to the current plan.  */
     aFrom[0].isOrdered = nLoop>0 ? -1 : nOrderBy;
@@ skipping 153 matching lines @@
               mxCost = pTo->rCost;
               mxUnsorted = pTo->rUnsorted;
               mxI = jj;
             }
           }
         }
       }
     }
 
 #ifdef WHERETRACE_ENABLED  /* >=2 */
-    if( sqlite3WhereTrace>=2 ){
+    if( sqlite3WhereTrace & 0x02 ){
       sqlite3DebugPrintf("---- after round %d ----\n", iLoop);
       for(ii=0, pTo=aTo; ii<nTo; ii++, pTo++){
         sqlite3DebugPrintf(" %s cost=%-3d nrow=%-3d order=%c",
            wherePathName(pTo, iLoop+1, 0), pTo->rCost, pTo->nRow,
            pTo->isOrdered>=0 ? (pTo->isOrdered+'0') : '?');
         if( pTo->isOrdered>0 ){
           sqlite3DebugPrintf(" rev=0x%llx\n", pTo->revLoop);
         }else{
           sqlite3DebugPrintf("\n");
         }
@@ skipping 43 matching lines @@
     if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
       if( pFrom->isOrdered==pWInfo->pOrderBy->nExpr ){
         pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
       }
     }else{
       pWInfo->nOBSat = pFrom->isOrdered;
       if( pWInfo->nOBSat<0 ) pWInfo->nOBSat = 0;
       pWInfo->revMask = pFrom->revLoop;
     }
     if( (pWInfo->wctrlFlags & WHERE_SORTBYGROUP)
-        && pWInfo->nOBSat==pWInfo->pOrderBy->nExpr
+        && pWInfo->nOBSat==pWInfo->pOrderBy->nExpr && nLoop>0
     ){
       Bitmask revMask = 0;
       int nOrder = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pOrderBy, 
           pFrom, 0, nLoop-1, pFrom->aLoop[nLoop-1], &revMask
       );
       assert( pWInfo->sorted==0 );
       if( nOrder==pWInfo->pOrderBy->nExpr ){
         pWInfo->sorted = 1;
         pWInfo->revMask = revMask;
       }
@@ skipping 29 matching lines @@
   int j;
   Table *pTab;
   Index *pIdx;
   
   pWInfo = pBuilder->pWInfo;
   if( pWInfo->wctrlFlags & WHERE_FORCE_TABLE ) return 0;
   assert( pWInfo->pTabList->nSrc>=1 );
   pItem = pWInfo->pTabList->a;
   pTab = pItem->pTab;
   if( IsVirtual(pTab) ) return 0;
-  if( pItem->zIndex ) return 0;
+  if( pItem->fg.isIndexedBy ) return 0;
   iCur = pItem->iCursor;
   pWC = &pWInfo->sWC;
   pLoop = pBuilder->pNew;
   pLoop->wsFlags = 0;
-  pLoop->u.btree.nSkip = 0;
-  pTerm = findTerm(pWC, iCur, -1, 0, WO_EQ, 0);
+  pLoop->nSkip = 0;
+  pTerm = sqlite3WhereFindTerm(pWC, iCur, -1, 0, WO_EQ|WO_IS, 0);
   if( pTerm ){
+    testcase( pTerm->eOperator & WO_IS );
     pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_IPK|WHERE_ONEROW;
     pLoop->aLTerm[0] = pTerm;
     pLoop->nLTerm = 1;
     pLoop->u.btree.nEq = 1;
     /* TUNING: Cost of a rowid lookup is 10 */
     pLoop->rRun = 33;  /* 33==sqlite3LogEst(10) */
   }else{
     for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      int opMask;
       assert( pLoop->aLTermSpace==pLoop->aLTerm );
-      assert( ArraySize(pLoop->aLTermSpace)==4 );
       if( !IsUniqueIndex(pIdx)
        || pIdx->pPartIdxWhere!=0 
        || pIdx->nKeyCol>ArraySize(pLoop->aLTermSpace) 
       ) continue;
+      opMask = pIdx->uniqNotNull ? (WO_EQ|WO_IS) : WO_EQ;
       for(j=0; j<pIdx->nKeyCol; j++){
-        pTerm = findTerm(pWC, iCur, pIdx->aiColumn[j], 0, WO_EQ, pIdx);
+        pTerm = sqlite3WhereFindTerm(pWC, iCur, j, 0, opMask, pIdx);
         if( pTerm==0 ) break;
+        testcase( pTerm->eOperator & WO_IS );
         pLoop->aLTerm[j] = pTerm;
       }
       if( j!=pIdx->nKeyCol ) continue;
       pLoop->wsFlags = WHERE_COLUMN_EQ|WHERE_ONEROW|WHERE_INDEXED;
       if( pIdx->isCovering || (pItem->colUsed & ~columnsInIndex(pIdx))==0 ){
         pLoop->wsFlags |= WHERE_IDX_ONLY;
       }
       pLoop->nLTerm = j;
       pLoop->u.btree.nEq = j;
       pLoop->u.btree.pIndex = pIdx;
       /* TUNING: Cost of a unique index lookup is 15 */
       pLoop->rRun = 39;  /* 39==sqlite3LogEst(15) */
       break;
     }
   }
   if( pLoop->wsFlags ){
     pLoop->nOut = (LogEst)1;
     pWInfo->a[0].pWLoop = pLoop;
-    pLoop->maskSelf = getMask(&pWInfo->sMaskSet, iCur);
+    pLoop->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, iCur);
     pWInfo->a[0].iTabCur = iCur;
     pWInfo->nRowOut = 1;
     if( pWInfo->pOrderBy ) pWInfo->nOBSat =  pWInfo->pOrderBy->nExpr;
     if( pWInfo->wctrlFlags & WHERE_WANT_DISTINCT ){
       pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
     }
 #ifdef SQLITE_DEBUG
     pLoop->cId = '0';
 #endif
     return 1;
@@ skipping 103 matching lines @@
   WhereInfo *pWInfo;         /* Will become the return value of this function */
   Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
   Bitmask notReady;          /* Cursors that are not yet positioned */
   WhereLoopBuilder sWLB;     /* The WhereLoop builder */
   WhereMaskSet *pMaskSet;    /* The expression mask set */
   WhereLevel *pLevel;        /* A single level in pWInfo->a[] */
   WhereLoop *pLoop;          /* Pointer to a single WhereLoop object */
   int ii;                    /* Loop counter */
   sqlite3 *db;               /* Database connection */
   int rc;                    /* Return code */
+  u8 bFordelete = 0;
 
+  assert( (wctrlFlags & WHERE_ONEPASS_MULTIROW)==0 || (
+        (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 
+     && (wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0 
+  ));
 
   /* Variable initialization */
   db = pParse->db;
   memset(&sWLB, 0, sizeof(sWLB));
 
   /* An ORDER/GROUP BY clause of more than 63 terms cannot be optimized */
   testcase( pOrderBy && pOrderBy->nExpr==BMS-1 );
   if( pOrderBy && pOrderBy->nExpr>=BMS ) pOrderBy = 0;
   sWLB.pOrderBy = pOrderBy;
 
@@ skipping 35 matching lines @@
   }
   pWInfo->aiCurOnePass[0] = pWInfo->aiCurOnePass[1] = -1;
   pWInfo->nLevel = nTabList;
   pWInfo->pParse = pParse;
   pWInfo->pTabList = pTabList;
   pWInfo->pOrderBy = pOrderBy;
   pWInfo->pResultSet = pResultSet;
   pWInfo->iBreak = pWInfo->iContinue = sqlite3VdbeMakeLabel(v);
   pWInfo->wctrlFlags = wctrlFlags;
   pWInfo->savedNQueryLoop = pParse->nQueryLoop;
+  assert( pWInfo->eOnePass==ONEPASS_OFF );  /* ONEPASS defaults to OFF */
   pMaskSet = &pWInfo->sMaskSet;
   sWLB.pWInfo = pWInfo;
   sWLB.pWC = &pWInfo->sWC;
   sWLB.pNew = (WhereLoop*)(((char*)pWInfo)+nByteWInfo);
   assert( EIGHT_BYTE_ALIGNMENT(sWLB.pNew) );
   whereLoopInit(sWLB.pNew);
 #ifdef SQLITE_DEBUG
   sWLB.pNew->cId = '*';
 #endif
 
   /* Split the WHERE clause into separate subexpressions where each
   ** subexpression is separated by an AND operator.
   */
   initMaskSet(pMaskSet);
-  whereClauseInit(&pWInfo->sWC, pWInfo);
-  whereSplit(&pWInfo->sWC, pWhere, TK_AND);
+  sqlite3WhereClauseInit(&pWInfo->sWC, pWInfo);
+  sqlite3WhereSplit(&pWInfo->sWC, pWhere, TK_AND);
     
   /* Special case: a WHERE clause that is constant.  Evaluate the
   ** expression and either jump over all of the code or fall thru.
   */
   for(ii=0; ii<sWLB.pWC->nTerm; ii++){
     if( nTabList==0 || sqlite3ExprIsConstantNotJoin(sWLB.pWC->a[ii].pExpr) ){
       sqlite3ExprIfFalse(pParse, sWLB.pWC->a[ii].pExpr, pWInfo->iBreak,
                          SQLITE_JUMPIFNULL);
       sWLB.pWC->a[ii].wtFlags |= TERM_CODED;
     }
   }
 
   /* Special case: No FROM clause
   */
   if( nTabList==0 ){
     if( pOrderBy ) pWInfo->nOBSat = pOrderBy->nExpr;
     if( wctrlFlags & WHERE_WANT_DISTINCT ){
       pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
     }
   }
 
   /* Assign a bit from the bitmask to every term in the FROM clause.
   **
-  ** When assigning bitmask values to FROM clause cursors, it must be
-  ** the case that if X is the bitmask for the N-th FROM clause term then
-  ** the bitmask for all FROM clause terms to the left of the N-th term
-  ** is (X-1).   An expression from the ON clause of a LEFT JOIN can use
-  ** its Expr.iRightJoinTable value to find the bitmask of the right table
-  ** of the join.  Subtracting one from the right table bitmask gives a
-  ** bitmask for all tables to the left of the join.  Knowing the bitmask
-  ** for all tables to the left of a left join is important.  Ticket #3015.
+  ** The N-th term of the FROM clause is assigned a bitmask of 1<<N.
+  **
+  ** The rule of the previous sentence ensures thta if X is the bitmask for
+  ** a table T, then X-1 is the bitmask for all other tables to the left of T.
+  ** Knowing the bitmask for all tables to the left of a left join is
+  ** important.  Ticket #3015.
   **
   ** Note that bitmasks are created for all pTabList->nSrc tables in
   ** pTabList, not just the first nTabList tables.  nTabList is normally
   ** equal to pTabList->nSrc but might be shortened to 1 if the
   ** WHERE_ONETABLE_ONLY flag is set.
   */
   for(ii=0; ii<pTabList->nSrc; ii++){
     createMask(pMaskSet, pTabList->a[ii].iCursor);
+    sqlite3WhereTabFuncArgs(pParse, &pTabList->a[ii], &pWInfo->sWC);
   }
-#ifndef NDEBUG
-  {
-    Bitmask toTheLeft = 0;
-    for(ii=0; ii<pTabList->nSrc; ii++){
-      Bitmask m = getMask(pMaskSet, pTabList->a[ii].iCursor);
-      assert( (m-1)==toTheLeft );
-      toTheLeft |= m;
-    }
+#ifdef SQLITE_DEBUG
+  for(ii=0; ii<pTabList->nSrc; ii++){
+    Bitmask m = sqlite3WhereGetMask(pMaskSet, pTabList->a[ii].iCursor);
+    assert( m==MASKBIT(ii) );
   }
 #endif
 
-  /* Analyze all of the subexpressions.  Note that exprAnalyze() might
-  ** add new virtual terms onto the end of the WHERE clause.  We do not
-  ** want to analyze these virtual terms, so start analyzing at the end
-  ** and work forward so that the added virtual terms are never processed.
-  */
-  exprAnalyzeAll(pTabList, &pWInfo->sWC);
-  if( db->mallocFailed ){
-    goto whereBeginError;
-  }
+  /* Analyze all of the subexpressions. */
+  sqlite3WhereExprAnalyze(pTabList, &pWInfo->sWC);
+  if( db->mallocFailed ) goto whereBeginError;
 
   if( wctrlFlags & WHERE_WANT_DISTINCT ){
     if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
       /* The DISTINCT marking is pointless.  Ignore it. */
       pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
     }else if( pOrderBy==0 ){
       /* Try to ORDER BY the result set to make distinct processing easier */
       pWInfo->wctrlFlags |= WHERE_DISTINCTBY;
       pWInfo->pOrderBy = pResultSet;
     }
   }
 
   /* Construct the WhereLoop objects */
-  WHERETRACE(0xffff,("*** Optimizer Start ***\n"));
+  WHERETRACE(0xffff,("*** Optimizer Start *** (wctrlFlags: 0x%x)\n",
+             wctrlFlags));
 #if defined(WHERETRACE_ENABLED)
-  /* Display all terms of the WHERE clause */
-  if( sqlite3WhereTrace & 0x100 ){
+  if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
     int i;
     for(i=0; i<sWLB.pWC->nTerm; i++){
       whereTermPrint(&sWLB.pWC->a[i], i);
     }
   }
 #endif
 
   if( nTabList!=1 || whereShortCut(&sWLB)==0 ){
     rc = whereLoopAddAll(&sWLB);
     if( rc ) goto whereBeginError;
   
-    /* Display all of the WhereLoop objects if wheretrace is enabled */
-#ifdef WHERETRACE_ENABLED /* !=0 */
-    if( sqlite3WhereTrace ){
+#ifdef WHERETRACE_ENABLED
+    if( sqlite3WhereTrace ){    /* Display all of the WhereLoop objects */
       WhereLoop *p;
       int i;
-      static char zLabel[] = "0123456789abcdefghijklmnopqrstuvwyxz"
-                                       "ABCDEFGHIJKLMNOPQRSTUVWYXZ";
+      static const char zLabel[] = "0123456789abcdefghijklmnopqrstuvwyxz"
+                                             "ABCDEFGHIJKLMNOPQRSTUVWYXZ";
       for(p=pWInfo->pLoops, i=0; p; p=p->pNextLoop, i++){
         p->cId = zLabel[i%sizeof(zLabel)];
         whereLoopPrint(p, sWLB.pWC);
       }
     }
 #endif
   
     wherePathSolver(pWInfo, 0);
     if( db->mallocFailed ) goto whereBeginError;
     if( pWInfo->pOrderBy ){
        wherePathSolver(pWInfo, pWInfo->nRowOut+1);
        if( db->mallocFailed ) goto whereBeginError;
     }
   }
   if( pWInfo->pOrderBy==0 && (db->flags & SQLITE_ReverseOrder)!=0 ){
      pWInfo->revMask = (Bitmask)(-1);
   }
   if( pParse->nErr || NEVER(db->mallocFailed) ){
     goto whereBeginError;
   }
-#ifdef WHERETRACE_ENABLED /* !=0 */
+#ifdef WHERETRACE_ENABLED
   if( sqlite3WhereTrace ){
-    int ii;
     sqlite3DebugPrintf("---- Solution nRow=%d", pWInfo->nRowOut);
     if( pWInfo->nOBSat>0 ){
       sqlite3DebugPrintf(" ORDERBY=%d,0x%llx", pWInfo->nOBSat, pWInfo->revMask);
     }
     switch( pWInfo->eDistinct ){
       case WHERE_DISTINCT_UNIQUE: {
         sqlite3DebugPrintf("  DISTINCT=unique");
         break;
       }
       case WHERE_DISTINCT_ORDERED: {
         sqlite3DebugPrintf("  DISTINCT=ordered");
         break;
       }
       case WHERE_DISTINCT_UNORDERED: {
         sqlite3DebugPrintf("  DISTINCT=unordered");
         break;
       }
     }
     sqlite3DebugPrintf("\n");
     for(ii=0; ii<pWInfo->nLevel; ii++){
       whereLoopPrint(pWInfo->a[ii].pWLoop, sWLB.pWC);
     }
   }
 #endif
   /* Attempt to omit tables from the join that do not effect the result */
   if( pWInfo->nLevel>=2
    && pResultSet!=0
    && OptimizationEnabled(db, SQLITE_OmitNoopJoin)
   ){
-    Bitmask tabUsed = exprListTableUsage(pMaskSet, pResultSet);
-    if( sWLB.pOrderBy ) tabUsed |= exprListTableUsage(pMaskSet, sWLB.pOrderBy);
+    Bitmask tabUsed = sqlite3WhereExprListUsage(pMaskSet, pResultSet);
+    if( sWLB.pOrderBy ){
+      tabUsed |= sqlite3WhereExprListUsage(pMaskSet, sWLB.pOrderBy);
+    }
     while( pWInfo->nLevel>=2 ){
       WhereTerm *pTerm, *pEnd;
       pLoop = pWInfo->a[pWInfo->nLevel-1].pWLoop;
-      if( (pWInfo->pTabList->a[pLoop->iTab].jointype & JT_LEFT)==0 ) break;
+      if( (pWInfo->pTabList->a[pLoop->iTab].fg.jointype & JT_LEFT)==0 ) break;
       if( (wctrlFlags & WHERE_WANT_DISTINCT)==0
        && (pLoop->wsFlags & WHERE_ONEROW)==0
       ){
         break;
       }
       if( (tabUsed & pLoop->maskSelf)!=0 ) break;
       pEnd = sWLB.pWC->a + sWLB.pWC->nTerm;
       for(pTerm=sWLB.pWC->a; pTerm<pEnd; pTerm++){
         if( (pTerm->prereqAll & pLoop->maskSelf)!=0
          && !ExprHasProperty(pTerm->pExpr, EP_FromJoin)
         ){
           break;
         }
       }
       if( pTerm<pEnd ) break;
       WHERETRACE(0xffff, ("-> drop loop %c not used\n", pLoop->cId));
       pWInfo->nLevel--;
       nTabList--;
     }
   }
   WHERETRACE(0xffff,("*** Optimizer Finished ***\n"));
   pWInfo->pParse->nQueryLoop += pWInfo->nRowOut;
 
   /* If the caller is an UPDATE or DELETE statement that is requesting
   ** to use a one-pass algorithm, determine if this is appropriate.
   ** The one-pass algorithm only works if the WHERE clause constrains
-  ** the statement to update a single row.
+  ** the statement to update or delete a single row.
   */
   assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
-  if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 
-   && (pWInfo->a[0].pWLoop->wsFlags & WHERE_ONEROW)!=0 ){
-    pWInfo->okOnePass = 1;
-    if( HasRowid(pTabList->a[0].pTab) ){
-      pWInfo->a[0].pWLoop->wsFlags &= ~WHERE_IDX_ONLY;
+  if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 ){
+    int wsFlags = pWInfo->a[0].pWLoop->wsFlags;
+    int bOnerow = (wsFlags & WHERE_ONEROW)!=0;
+    if( bOnerow || ( (wctrlFlags & WHERE_ONEPASS_MULTIROW)
+       && 0==(wsFlags & WHERE_VIRTUALTABLE)
+    )){
+      pWInfo->eOnePass = bOnerow ? ONEPASS_SINGLE : ONEPASS_MULTI;
+      if( HasRowid(pTabList->a[0].pTab) && (wsFlags & WHERE_IDX_ONLY) ){
+        if( wctrlFlags & WHERE_ONEPASS_MULTIROW ){
+          bFordelete = OPFLAG_FORDELETE;
+        }
+        pWInfo->a[0].pWLoop->wsFlags = (wsFlags & ~WHERE_IDX_ONLY);
+      }
     }
   }
 
   /* Open all tables in the pTabList and any indices selected for
   ** searching those tables.
   */
-  notReady = ~(Bitmask)0;
   for(ii=0, pLevel=pWInfo->a; ii<nTabList; ii++, pLevel++){
     Table *pTab;     /* Table to open */
     int iDb;         /* Index of database containing table/index */
     struct SrcList_item *pTabItem;
 
     pTabItem = &pTabList->a[pLevel->iFrom];
     pTab = pTabItem->pTab;
     iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
     pLoop = pLevel->pWLoop;
     if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
       /* Do nothing */
     }else
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
       const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
       int iCur = pTabItem->iCursor;
       sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
     }else if( IsVirtual(pTab) ){
       /* noop */
     }else
 #endif
     if( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
          && (wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0 ){
       int op = OP_OpenRead;
-      if( pWInfo->okOnePass ){
+      if( pWInfo->eOnePass!=ONEPASS_OFF ){
         op = OP_OpenWrite;
         pWInfo->aiCurOnePass[0] = pTabItem->iCursor;
       };
       sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
       assert( pTabItem->iCursor==pLevel->iTabCur );
-      testcase( !pWInfo->okOnePass && pTab->nCol==BMS-1 );
-      testcase( !pWInfo->okOnePass && pTab->nCol==BMS );
-      if( !pWInfo->okOnePass && pTab->nCol<BMS && HasRowid(pTab) ){
+      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS-1 );
+      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS );
+      if( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol<BMS && HasRowid(pTab) ){
         Bitmask b = pTabItem->colUsed;
         int n = 0;
         for(; b; b=b>>1, n++){}
         sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1, 
                             SQLITE_INT_TO_PTR(n), P4_INT32);
         assert( n<=pTab->nCol );
       }
+#ifdef SQLITE_ENABLE_CURSOR_HINTS
+      if( pLoop->u.btree.pIndex!=0 ){
+        sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ|bFordelete);
+      }else
+#endif
+      {
+        sqlite3VdbeChangeP5(v, bFordelete);
+      }
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+      sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, pTabItem->iCursor, 0, 0,
+                            (const u8*)&pTabItem->colUsed, P4_INT64);
+#endif
     }else{
       sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
     }
     if( pLoop->wsFlags & WHERE_INDEXED ){
       Index *pIx = pLoop->u.btree.pIndex;
       int iIndexCur;
       int op = OP_OpenRead;
       /* iIdxCur is always set if to a positive value if ONEPASS is possible */
       assert( iIdxCur!=0 || (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 );
       if( !HasRowid(pTab) && IsPrimaryKeyIndex(pIx)
        && (wctrlFlags & WHERE_ONETABLE_ONLY)!=0
       ){
         /* This is one term of an OR-optimization using the PRIMARY KEY of a
         ** WITHOUT ROWID table.  No need for a separate index */
         iIndexCur = pLevel->iTabCur;
         op = 0;
-      }else if( pWInfo->okOnePass ){
+      }else if( pWInfo->eOnePass!=ONEPASS_OFF ){
         Index *pJ = pTabItem->pTab->pIndex;
         iIndexCur = iIdxCur;
         assert( wctrlFlags & WHERE_ONEPASS_DESIRED );
         while( ALWAYS(pJ) && pJ!=pIx ){
           iIndexCur++;
           pJ = pJ->pNext;
         }
         op = OP_OpenWrite;
         pWInfo->aiCurOnePass[1] = iIndexCur;
       }else if( iIdxCur && (wctrlFlags & WHERE_ONETABLE_ONLY)!=0 ){
         iIndexCur = iIdxCur;
         if( wctrlFlags & WHERE_REOPEN_IDX ) op = OP_ReopenIdx;
       }else{
         iIndexCur = pParse->nTab++;
       }
       pLevel->iIdxCur = iIndexCur;
       assert( pIx->pSchema==pTab->pSchema );
       assert( iIndexCur>=0 );
       if( op ){
         sqlite3VdbeAddOp3(v, op, iIndexCur, pIx->tnum, iDb);
         sqlite3VdbeSetP4KeyInfo(pParse, pIx);
+        if( (pLoop->wsFlags & WHERE_CONSTRAINT)!=0
+         && (pLoop->wsFlags & (WHERE_COLUMN_RANGE|WHERE_SKIPSCAN))==0
+         && (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0
+        ){
+          sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ); /* Hint to COMDB2 */
+        }
         VdbeComment((v, "%s", pIx->zName));
+#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
+        {
+          u64 colUsed = 0;
+          int ii, jj;
+          for(ii=0; ii<pIx->nColumn; ii++){
+            jj = pIx->aiColumn[ii];
+            if( jj<0 ) continue;
+            if( jj>63 ) jj = 63;
+            if( (pTabItem->colUsed & MASKBIT(jj))==0 ) continue;
+            colUsed |= ((u64)1)<<(ii<63 ? ii : 63);
+          }
+          sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, iIndexCur, 0, 0,
+                                (u8*)&colUsed, P4_INT64);
+        }
+#endif /* SQLITE_ENABLE_COLUMN_USED_MASK */
       }
     }
     if( iDb>=0 ) sqlite3CodeVerifySchema(pParse, iDb);
-    notReady &= ~getMask(&pWInfo->sMaskSet, pTabItem->iCursor);
   }
   pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
   if( db->mallocFailed ) goto whereBeginError;
 
   /* Generate the code to do the search.  Each iteration of the for
   ** loop below generates code for a single nested loop of the VM
   ** program.
   */
   notReady = ~(Bitmask)0;
   for(ii=0; ii<nTabList; ii++){
+    int addrExplain;
+    int wsFlags;
     pLevel = &pWInfo->a[ii];
+    wsFlags = pLevel->pWLoop->wsFlags;
 #ifndef SQLITE_OMIT_AUTOMATIC_INDEX
     if( (pLevel->pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 ){
       constructAutomaticIndex(pParse, &pWInfo->sWC,
                 &pTabList->a[pLevel->iFrom], notReady, pLevel);
       if( db->mallocFailed ) goto whereBeginError;
     }
 #endif
-    explainOneScan(pParse, pTabList, pLevel, ii, pLevel->iFrom, wctrlFlags);
+    addrExplain = sqlite3WhereExplainOneScan(
+        pParse, pTabList, pLevel, ii, pLevel->iFrom, wctrlFlags
+    );
     pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
-    notReady = codeOneLoopStart(pWInfo, ii, notReady);
+    notReady = sqlite3WhereCodeOneLoopStart(pWInfo, ii, notReady);
     pWInfo->iContinue = pLevel->addrCont;
+    if( (wsFlags&WHERE_MULTI_OR)==0 && (wctrlFlags&WHERE_ONETABLE_ONLY)==0 ){
+      sqlite3WhereAddScanStatus(v, pTabList, pLevel, addrExplain);
+    }
   }
 
   /* Done. */
   VdbeModuleComment((v, "Begin WHERE-core"));
   return pWInfo;
 
   /* Jump here if malloc fails */
 whereBeginError:
   if( pWInfo ){
     pParse->nQueryLoop = pWInfo->savedNQueryLoop;
@@ skipping 37 matching lines @@
       int j;
       sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
       for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
         sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
         sqlite3VdbeAddOp2(v, pIn->eEndLoopOp, pIn->iCur, pIn->addrInTop);
         VdbeCoverage(v);
         VdbeCoverageIf(v, pIn->eEndLoopOp==OP_PrevIfOpen);
         VdbeCoverageIf(v, pIn->eEndLoopOp==OP_NextIfOpen);
         sqlite3VdbeJumpHere(v, pIn->addrInTop-1);
       }
-      sqlite3DbFree(db, pLevel->u.in.aInLoop);
     }
     sqlite3VdbeResolveLabel(v, pLevel->addrBrk);
     if( pLevel->addrSkip ){
-      sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrSkip);
+      sqlite3VdbeGoto(v, pLevel->addrSkip);
       VdbeComment((v, "next skip-scan on %s", pLoop->u.btree.pIndex->zName));
       sqlite3VdbeJumpHere(v, pLevel->addrSkip);
       sqlite3VdbeJumpHere(v, pLevel->addrSkip-2);
     }
+#ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
+    if( pLevel->addrLikeRep ){
+      int op;
+      if( sqlite3VdbeGetOp(v, pLevel->addrLikeRep-1)->p1 ){
+        op = OP_DecrJumpZero;
+      }else{
+        op = OP_JumpZeroIncr;
+      }
+      sqlite3VdbeAddOp2(v, op, pLevel->iLikeRepCntr, pLevel->addrLikeRep);
+      VdbeCoverage(v);
+    }
+#endif
     if( pLevel->iLeftJoin ){
       addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin); VdbeCoverage(v);
       assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
            || (pLoop->wsFlags & WHERE_INDEXED)!=0 );
       if( (pLoop->wsFlags & WHERE_IDX_ONLY)==0 ){
         sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
       }
       if( pLoop->wsFlags & WHERE_INDEXED ){
         sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
       }
       if( pLevel->op==OP_Return ){
         sqlite3VdbeAddOp2(v, OP_Gosub, pLevel->p1, pLevel->addrFirst);
       }else{
-        sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrFirst);
+        sqlite3VdbeGoto(v, pLevel->addrFirst);
       }
       sqlite3VdbeJumpHere(v, addr);
     }
     VdbeModuleComment((v, "End WHERE-loop%d: %s", i,
                      pWInfo->pTabList->a[pLevel->iFrom].pTab->zName));
   }
 
   /* The "break" point is here, just past the end of the outer loop.
   ** Set it.
   */
   sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
 
   assert( pWInfo->nLevel<=pTabList->nSrc );
   for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
     int k, last;
     VdbeOp *pOp;
     Index *pIdx = 0;
     struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
     Table *pTab = pTabItem->pTab;
     assert( pTab!=0 );
     pLoop = pLevel->pWLoop;
 
     /* For a co-routine, change all OP_Column references to the table of
-    ** the co-routine into OP_SCopy of result contained in a register.
+    ** the co-routine into OP_Copy of result contained in a register.
     ** OP_Rowid becomes OP_Null.
     */
-    if( pTabItem->viaCoroutine && !db->mallocFailed ){
-      last = sqlite3VdbeCurrentAddr(v);
-      k = pLevel->addrBody;
-      pOp = sqlite3VdbeGetOp(v, k);
-      for(; k<last; k++, pOp++){
-        if( pOp->p1!=pLevel->iTabCur ) continue;
-        if( pOp->opcode==OP_Column ){
-          pOp->opcode = OP_Copy;
-          pOp->p1 = pOp->p2 + pTabItem->regResult;
-          pOp->p2 = pOp->p3;
-          pOp->p3 = 0;
-        }else if( pOp->opcode==OP_Rowid ){
-          pOp->opcode = OP_Null;
-          pOp->p1 = 0;
-          pOp->p3 = 0;
-        }
-      }
+    if( pTabItem->fg.viaCoroutine && !db->mallocFailed ){
+      translateColumnToCopy(v, pLevel->addrBody, pLevel->iTabCur,
+                            pTabItem->regResult, 0);
       continue;
     }
 
     /* Close all of the cursors that were opened by sqlite3WhereBegin.
     ** Except, do not close cursors that will be reused by the OR optimization
     ** (WHERE_OMIT_OPEN_CLOSE).  And do not close the OP_OpenWrite cursors
     ** created for the ONEPASS optimization.
     */
     if( (pTab->tabFlags & TF_Ephemeral)==0
      && pTab->pSelect==0
      && (pWInfo->wctrlFlags & WHERE_OMIT_OPEN_CLOSE)==0
     ){
       int ws = pLoop->wsFlags;
-      if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
+      if( pWInfo->eOnePass==ONEPASS_OFF && (ws & WHERE_IDX_ONLY)==0 ){
         sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
       }
       if( (ws & WHERE_INDEXED)!=0
        && (ws & (WHERE_IPK|WHERE_AUTO_INDEX))==0 
        && pLevel->iIdxCur!=pWInfo->aiCurOnePass[1]
       ){
         sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
       }
     }
 
     /* If this scan uses an index, make VDBE code substitutions to read data
     ** from the index instead of from the table where possible.  In some cases
     ** this optimization prevents the table from ever being read, which can
     ** yield a significant performance boost.
     ** 
     ** Calls to the code generator in between sqlite3WhereBegin and
     ** sqlite3WhereEnd will have created code that references the table
     ** directly.  This loop scans all that code looking for opcodes
     ** that reference the table and converts them into opcodes that
     ** reference the index.
     */
     if( pLoop->wsFlags & (WHERE_INDEXED|WHERE_IDX_ONLY) ){
       pIdx = pLoop->u.btree.pIndex;
     }else if( pLoop->wsFlags & WHERE_MULTI_OR ){
       pIdx = pLevel->u.pCovidx;
     }
-    if( pIdx && !db->mallocFailed ){
+    if( pIdx
+     && (pWInfo->eOnePass==ONEPASS_OFF || !HasRowid(pIdx->pTable))
+     && !db->mallocFailed
+    ){
       last = sqlite3VdbeCurrentAddr(v);
       k = pLevel->addrBody;
       pOp = sqlite3VdbeGetOp(v, k);
       for(; k<last; k++, pOp++){
         if( pOp->p1!=pLevel->iTabCur ) continue;
         if( pOp->opcode==OP_Column ){
           int x = pOp->p2;
           assert( pIdx->pTable==pTab );
           if( !HasRowid(pTab) ){
             Index *pPk = sqlite3PrimaryKeyIndex(pTab);
             x = pPk->aiColumn[x];
+            assert( x>=0 );
           }
           x = sqlite3ColumnOfIndex(pIdx, x);
           if( x>=0 ){
             pOp->p2 = x;
             pOp->p1 = pLevel->iIdxCur;
           }
           assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0 || x>=0 );
         }else if( pOp->opcode==OP_Rowid ){
           pOp->p1 = pLevel->iIdxCur;
           pOp->opcode = OP_IdxRowid;
         }
       }
     }
   }
 
   /* Final cleanup
   */
   pParse->nQueryLoop = pWInfo->savedNQueryLoop;
   whereInfoFree(db, pWInfo);
   return;
 }