Add //third_party/sqlite to dirs_to_snapshot, remove net_sql.patch

third_party/sqlite/src/ext/fts3/fts3_expr.c

 /*
 ** 2008 Nov 28
 **
 ** 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 code that implements a parser for fts3 query strings
 ** (the right-hand argument to the MATCH operator). Because the supported 
 ** syntax is relatively simple, the whole tokenizer/parser system is
 ** hand-coded. 
 */
+#include "fts3Int.h"
 #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
 
 /*
 ** By default, this module parses the legacy syntax that has been 
 ** traditionally used by fts3. Or, if SQLITE_ENABLE_FTS3_PARENTHESIS
 ** is defined, then it uses the new syntax. The differences between
 ** the new and the old syntaxes are:
 **
 **  a) The new syntax supports parenthesis. The old does not.
 **
@@ skipping 42 matching lines @@
 # else
 #  define sqlite3_fts3_enable_parentheses 0
 # endif
 #endif
 
 /*
 ** Default span for NEAR operators.
 */
 #define SQLITE_FTS3_DEFAULT_NEAR_PARAM 10
 
-#include "fts3Int.h"
 #include <string.h>
 #include <assert.h>
 
+/*
+** isNot:
+**   This variable is used by function getNextNode(). When getNextNode() is
+**   called, it sets ParseContext.isNot to true if the 'next node' is a 
+**   FTSQUERY_PHRASE with a unary "-" attached to it. i.e. "mysql" in the
+**   FTS3 query "sqlite -mysql". Otherwise, ParseContext.isNot is set to
+**   zero.
+*/
 typedef struct ParseContext ParseContext;
 struct ParseContext {
   sqlite3_tokenizer *pTokenizer;      /* Tokenizer module */
+  int iLangid;                        /* Language id used with tokenizer */
   const char **azCol;                 /* Array of column names for fts3 table */
+  int bFts4;                          /* True to allow FTS4-only syntax */
   int nCol;                           /* Number of entries in azCol[] */
   int iDefaultCol;                    /* Default column to query */
+  int isNot;                          /* True if getNextNode() sees a unary - */
   sqlite3_context *pCtx;              /* Write error message here */
   int nNest;                          /* Number of nested brackets */
 };
 
 /*
 ** This function is equivalent to the standard isspace() function. 
 **
 ** The standard isspace() can be awkward to use safely, because although it
-** is defined to accept an argument of type int, its behaviour when passed
+** is defined to accept an argument of type int, its behavior when passed
 ** an integer that falls outside of the range of the unsigned char type
 ** is undefined (and sometimes, "undefined" means segfault). This wrapper
 ** is defined to accept an argument of type char, and always returns 0 for
 ** any values that fall outside of the range of the unsigned char type (i.e.
 ** negative values).
 */
 static int fts3isspace(char c){
   return c==' ' || c=='\t' || c=='\n' || c=='\r' || c=='\v' || c=='\f';
 }
 
 /*
 ** Allocate nByte bytes of memory using sqlite3_malloc(). If successful,
 ** zero the memory before returning a pointer to it. If unsuccessful, 
 ** return NULL.
 */
 static void *fts3MallocZero(int nByte){
   void *pRet = sqlite3_malloc(nByte);
   if( pRet ) memset(pRet, 0, nByte);
   return pRet;
 }
 
+int sqlite3Fts3OpenTokenizer(
+  sqlite3_tokenizer *pTokenizer,
+  int iLangid,
+  const char *z,
+  int n,
+  sqlite3_tokenizer_cursor **ppCsr
+){
+  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
+  sqlite3_tokenizer_cursor *pCsr = 0;
+  int rc;
+
+  rc = pModule->xOpen(pTokenizer, z, n, &pCsr);
+  assert( rc==SQLITE_OK || pCsr==0 );
+  if( rc==SQLITE_OK ){
+    pCsr->pTokenizer = pTokenizer;
+    if( pModule->iVersion>=1 ){
+      rc = pModule->xLanguageid(pCsr, iLangid);
+      if( rc!=SQLITE_OK ){
+        pModule->xClose(pCsr);
+        pCsr = 0;
+      }
+    }
+  }
+  *ppCsr = pCsr;
+  return rc;
+}
+
+/*
+** Function getNextNode(), which is called by fts3ExprParse(), may itself
+** call fts3ExprParse(). So this forward declaration is required.
+*/
+static int fts3ExprParse(ParseContext *, const char *, int, Fts3Expr **, int *);
 
 /*
 ** Extract the next token from buffer z (length n) using the tokenizer
 ** and other information (column names etc.) in pParse. Create an Fts3Expr
 ** structure of type FTSQUERY_PHRASE containing a phrase consisting of this
 ** single token and set *ppExpr to point to it. If the end of the buffer is
 ** reached before a token is found, set *ppExpr to zero. It is the
 ** responsibility of the caller to eventually deallocate the allocated 
 ** Fts3Expr structure (if any) by passing it to sqlite3_free().
 **
 ** Return SQLITE_OK if successful, or SQLITE_NOMEM if a memory allocation
 ** fails.
 */
 static int getNextToken(
   ParseContext *pParse,                   /* fts3 query parse context */
   int iCol,                               /* Value for Fts3Phrase.iColumn */
   const char *z, int n,                   /* Input string */
   Fts3Expr **ppExpr,                      /* OUT: expression */
   int *pnConsumed                         /* OUT: Number of bytes consumed */
 ){
   sqlite3_tokenizer *pTokenizer = pParse->pTokenizer;
   sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
   int rc;
   sqlite3_tokenizer_cursor *pCursor;
   Fts3Expr *pRet = 0;
-  int nConsumed = 0;
+  int i = 0;
 
-  rc = pModule->xOpen(pTokenizer, z, n, &pCursor);
+  /* Set variable i to the maximum number of bytes of input to tokenize. */
+  for(i=0; i<n; i++){
+    if( sqlite3_fts3_enable_parentheses && (z[i]=='(' || z[i]==')') ) break;
+    if( z[i]=='"' ) break;
+  }
+
+  *pnConsumed = i;
+  rc = sqlite3Fts3OpenTokenizer(pTokenizer, pParse->iLangid, z, i, &pCursor);
   if( rc==SQLITE_OK ){
     const char *zToken;
-    int nToken, iStart, iEnd, iPosition;
+    int nToken = 0, iStart = 0, iEnd = 0, iPosition = 0;
     int nByte;                               /* total space to allocate */
 
-    pCursor->pTokenizer = pTokenizer;
     rc = pModule->xNext(pCursor, &zToken, &nToken, &iStart, &iEnd, &iPosition);
-
     if( rc==SQLITE_OK ){
       nByte = sizeof(Fts3Expr) + sizeof(Fts3Phrase) + nToken;
       pRet = (Fts3Expr *)fts3MallocZero(nByte);
       if( !pRet ){
         rc = SQLITE_NOMEM;
       }else{
         pRet->eType = FTSQUERY_PHRASE;
         pRet->pPhrase = (Fts3Phrase *)&pRet[1];
         pRet->pPhrase->nToken = 1;
         pRet->pPhrase->iColumn = iCol;
         pRet->pPhrase->aToken[0].n = nToken;
         pRet->pPhrase->aToken[0].z = (char *)&pRet->pPhrase[1];
         memcpy(pRet->pPhrase->aToken[0].z, zToken, nToken);
 
         if( iEnd<n && z[iEnd]=='*' ){
           pRet->pPhrase->aToken[0].isPrefix = 1;
           iEnd++;
         }
-        if( !sqlite3_fts3_enable_parentheses && iStart>0 && z[iStart-1]=='-' ){
-          pRet->pPhrase->isNot = 1;
+
+        while( 1 ){
+          if( !sqlite3_fts3_enable_parentheses 
+           && iStart>0 && z[iStart-1]=='-' 
+          ){
+            pParse->isNot = 1;
+            iStart--;
+          }else if( pParse->bFts4 && iStart>0 && z[iStart-1]=='^' ){
+            pRet->pPhrase->aToken[0].bFirst = 1;
+            iStart--;
+          }else{
+            break;
+          }
         }
+
       }
-      nConsumed = iEnd;
+      *pnConsumed = iEnd;
+    }else if( i && rc==SQLITE_DONE ){
+      rc = SQLITE_OK;
     }
 
     pModule->xClose(pCursor);
   }
   
-  *pnConsumed = nConsumed;
   *ppExpr = pRet;
   return rc;
 }
 
 
 /*
 ** Enlarge a memory allocation.  If an out-of-memory allocation occurs,
 ** then free the old allocation.
 */
 static void *fts3ReallocOrFree(void *pOrig, int nNew){
@@ skipping 22 matching lines @@
   Fts3Expr **ppExpr                       /* OUT: expression */
 ){
   sqlite3_tokenizer *pTokenizer = pParse->pTokenizer;
   sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
   int rc;
   Fts3Expr *p = 0;
   sqlite3_tokenizer_cursor *pCursor = 0;
   char *zTemp = 0;
   int nTemp = 0;
 
-  rc = pModule->xOpen(pTokenizer, zInput, nInput, &pCursor);
+  const int nSpace = sizeof(Fts3Expr) + sizeof(Fts3Phrase);
+  int nToken = 0;
+
+  /* The final Fts3Expr data structure, including the Fts3Phrase,
+  ** Fts3PhraseToken structures token buffers are all stored as a single 
+  ** allocation so that the expression can be freed with a single call to
+  ** sqlite3_free(). Setting this up requires a two pass approach.
+  **
+  ** The first pass, in the block below, uses a tokenizer cursor to iterate
+  ** through the tokens in the expression. This pass uses fts3ReallocOrFree()
+  ** to assemble data in two dynamic buffers:
+  **
+  **   Buffer p: Points to the Fts3Expr structure, followed by the Fts3Phrase
+  **             structure, followed by the array of Fts3PhraseToken 
+  **             structures. This pass only populates the Fts3PhraseToken array.
+  **
+  **   Buffer zTemp: Contains copies of all tokens.
+  **
+  ** The second pass, in the block that begins "if( rc==SQLITE_DONE )" below,
+  ** appends buffer zTemp to buffer p, and fills in the Fts3Expr and Fts3Phrase
+  ** structures.
+  */
+  rc = sqlite3Fts3OpenTokenizer(
+      pTokenizer, pParse->iLangid, zInput, nInput, &pCursor);
   if( rc==SQLITE_OK ){
     int ii;
-    pCursor->pTokenizer = pTokenizer;
     for(ii=0; rc==SQLITE_OK; ii++){
-      const char *zToken;
-      int nToken, iBegin, iEnd, iPos;
-      rc = pModule->xNext(pCursor, &zToken, &nToken, &iBegin, &iEnd, &iPos);
+      const char *zByte;
+      int nByte = 0, iBegin = 0, iEnd = 0, iPos = 0;
+      rc = pModule->xNext(pCursor, &zByte, &nByte, &iBegin, &iEnd, &iPos);
       if( rc==SQLITE_OK ){
-        int nByte = sizeof(Fts3Expr) + sizeof(Fts3Phrase);
-        p = fts3ReallocOrFree(p, nByte+ii*sizeof(Fts3PhraseToken));
-        zTemp = fts3ReallocOrFree(zTemp, nTemp + nToken);
-        if( !p || !zTemp ){
-          goto no_mem;
-        }
-        if( ii==0 ){
-          memset(p, 0, nByte);
-          p->pPhrase = (Fts3Phrase *)&p[1];
-        }
-        p->pPhrase = (Fts3Phrase *)&p[1];
-        memset(&p->pPhrase->aToken[ii], 0, sizeof(Fts3PhraseToken));
-        p->pPhrase->nToken = ii+1;
-        p->pPhrase->aToken[ii].n = nToken;
-        memcpy(&zTemp[nTemp], zToken, nToken);
-        nTemp += nToken;
-        if( iEnd<nInput && zInput[iEnd]=='*' ){
-          p->pPhrase->aToken[ii].isPrefix = 1;
-        }else{
-          p->pPhrase->aToken[ii].isPrefix = 0;
-        }
+        Fts3PhraseToken *pToken;
+
+        p = fts3ReallocOrFree(p, nSpace + ii*sizeof(Fts3PhraseToken));
+        if( !p ) goto no_mem;
+
+        zTemp = fts3ReallocOrFree(zTemp, nTemp + nByte);
+        if( !zTemp ) goto no_mem;
+
+        assert( nToken==ii );
+        pToken = &((Fts3Phrase *)(&p[1]))->aToken[ii];
+        memset(pToken, 0, sizeof(Fts3PhraseToken));
+
+        memcpy(&zTemp[nTemp], zByte, nByte);
+        nTemp += nByte;
+
+        pToken->n = nByte;
+        pToken->isPrefix = (iEnd<nInput && zInput[iEnd]=='*');
+        pToken->bFirst = (iBegin>0 && zInput[iBegin-1]=='^');
+        nToken = ii+1;
       }
     }
 
     pModule->xClose(pCursor);
     pCursor = 0;
   }
 
   if( rc==SQLITE_DONE ){
     int jj;
-    char *zNew = NULL;
-    int nNew = 0;
-    int nByte = sizeof(Fts3Expr) + sizeof(Fts3Phrase);
-    nByte += (p?(p->pPhrase->nToken-1):0) * sizeof(Fts3PhraseToken);
-    p = fts3ReallocOrFree(p, nByte + nTemp);
-    if( !p ){
-      goto no_mem;
+    char *zBuf = 0;
+
+    p = fts3ReallocOrFree(p, nSpace + nToken*sizeof(Fts3PhraseToken) + nTemp);
+    if( !p ) goto no_mem;
+    memset(p, 0, (char *)&(((Fts3Phrase *)&p[1])->aToken[0])-(char *)p);
+    p->eType = FTSQUERY_PHRASE;
+    p->pPhrase = (Fts3Phrase *)&p[1];
+    p->pPhrase->iColumn = pParse->iDefaultCol;
+    p->pPhrase->nToken = nToken;
+
+    zBuf = (char *)&p->pPhrase->aToken[nToken];
+    if( zTemp ){
+      memcpy(zBuf, zTemp, nTemp);
+      sqlite3_free(zTemp);
+    }else{
+      assert( nTemp==0 );
     }
-    if( zTemp ){
-      zNew = &(((char *)p)[nByte]);
-      memcpy(zNew, zTemp, nTemp);
-    }else{
-      memset(p, 0, nByte+nTemp);
+
+    for(jj=0; jj<p->pPhrase->nToken; jj++){
+      p->pPhrase->aToken[jj].z = zBuf;
+      zBuf += p->pPhrase->aToken[jj].n;
     }
-    p->pPhrase = (Fts3Phrase *)&p[1];
-    for(jj=0; jj<p->pPhrase->nToken; jj++){
-      p->pPhrase->aToken[jj].z = &zNew[nNew];
-      nNew += p->pPhrase->aToken[jj].n;
-    }
-    sqlite3_free(zTemp);
-    p->eType = FTSQUERY_PHRASE;
-    p->pPhrase->iColumn = pParse->iDefaultCol;
     rc = SQLITE_OK;
   }
 
   *ppExpr = p;
   return rc;
 no_mem:
 
   if( pCursor ){
     pModule->xClose(pCursor);
   }
   sqlite3_free(zTemp);
   sqlite3_free(p);
   *ppExpr = 0;
   return SQLITE_NOMEM;
 }
 
 /*
-** Function getNextNode(), which is called by fts3ExprParse(), may itself
-** call fts3ExprParse(). So this forward declaration is required.
-*/
-static int fts3ExprParse(ParseContext *, const char *, int, Fts3Expr **, int *);
-
-/*
 ** The output variable *ppExpr is populated with an allocated Fts3Expr 
 ** structure, or set to 0 if the end of the input buffer is reached.
 **
 ** Returns an SQLite error code. SQLITE_OK if everything works, SQLITE_NOMEM
 ** if a malloc failure occurs, or SQLITE_ERROR if a parse error is encountered.
 ** If SQLITE_ERROR is returned, pContext is populated with an error message.
 */
 static int getNextNode(
   ParseContext *pParse,                   /* fts3 query parse context */
   const char *z, int n,                   /* Input string */
@@ skipping 13 matching lines @@
   };
   int ii;
   int iCol;
   int iColLen;
   int rc;
   Fts3Expr *pRet = 0;
 
   const char *zInput = z;
   int nInput = n;
 
+  pParse->isNot = 0;
+
   /* Skip over any whitespace before checking for a keyword, an open or
   ** close bracket, or a quoted string. 
   */
   while( nInput>0 && fts3isspace(*zInput) ){
     nInput--;
     zInput++;
   }
   if( nInput==0 ){
     return SQLITE_DONE;
   }
@@ skipping 40 matching lines @@
         *pnConsumed = (int)((zInput - z) + nKey);
         return SQLITE_OK;
       }
 
       /* Turns out that wasn't a keyword after all. This happens if the
       ** user has supplied a token such as "ORacle". Continue.
       */
     }
   }
 
-  /* Check for an open bracket. */
-  if( sqlite3_fts3_enable_parentheses ){
-    if( *zInput=='(' ){
-      int nConsumed;
-      pParse->nNest++;
-      rc = fts3ExprParse(pParse, &zInput[1], nInput-1, ppExpr, &nConsumed);
-      if( rc==SQLITE_OK && !*ppExpr ){
-        rc = SQLITE_DONE;
-      }
-      *pnConsumed = (int)((zInput - z) + 1 + nConsumed);
-      return rc;
-    }
-  
-    /* Check for a close bracket. */
-    if( *zInput==')' ){
-      pParse->nNest--;
-      *pnConsumed = (int)((zInput - z) + 1);
-      return SQLITE_DONE;
-    }
-  }
-
   /* See if we are dealing with a quoted phrase. If this is the case, then
   ** search for the closing quote and pass the whole string to getNextString()
   ** for processing. This is easy to do, as fts3 has no syntax for escaping
   ** a quote character embedded in a string.
   */
   if( *zInput=='"' ){
     for(ii=1; ii<nInput && zInput[ii]!='"'; ii++);
     *pnConsumed = (int)((zInput - z) + ii + 1);
     if( ii==nInput ){
       return SQLITE_ERROR;
     }
     return getNextString(pParse, &zInput[1], ii-1, ppExpr);
   }
 
+  if( sqlite3_fts3_enable_parentheses ){
+    if( *zInput=='(' ){
+      int nConsumed = 0;
+      pParse->nNest++;
+      rc = fts3ExprParse(pParse, zInput+1, nInput-1, ppExpr, &nConsumed);
+      if( rc==SQLITE_OK && !*ppExpr ){ rc = SQLITE_DONE; }
+      *pnConsumed = (int)(zInput - z) + 1 + nConsumed;
+      return rc;
+    }else if( *zInput==')' ){
+      pParse->nNest--;
+      *pnConsumed = (int)((zInput - z) + 1);
+      *ppExpr = 0;
+      return SQLITE_DONE;
+    }
+  }
 
   /* If control flows to this point, this must be a regular token, or 
   ** the end of the input. Read a regular token using the sqlite3_tokenizer
   ** interface. Before doing so, figure out if there is an explicit
   ** column specifier for the token. 
   **
   ** TODO: Strangely, it is not possible to associate a column specifier
   ** with a quoted phrase, only with a single token. Not sure if this was
   ** an implementation artifact or an intentional decision when fts3 was
   ** first implemented. Whichever it was, this module duplicates the 
@@ skipping 98 matching lines @@
   Fts3Expr *pPrev = 0;
   Fts3Expr *pNotBranch = 0;               /* Only used in legacy parse mode */
   int nIn = n;
   const char *zIn = z;
   int rc = SQLITE_OK;
   int isRequirePhrase = 1;
 
   while( rc==SQLITE_OK ){
     Fts3Expr *p = 0;
     int nByte = 0;
+
     rc = getNextNode(pParse, zIn, nIn, &p, &nByte);
+    assert( nByte>0 || (rc!=SQLITE_OK && p==0) );
     if( rc==SQLITE_OK ){
-      int isPhrase;
+      if( p ){
+        int isPhrase;
 
-      if( !sqlite3_fts3_enable_parentheses 
-       && p->eType==FTSQUERY_PHRASE && p->pPhrase->isNot 
-      ){
-        /* Create an implicit NOT operator. */
-        Fts3Expr *pNot = fts3MallocZero(sizeof(Fts3Expr));
-        if( !pNot ){
-          sqlite3Fts3ExprFree(p);
-          rc = SQLITE_NOMEM;
-          goto exprparse_out;
-        }
-        pNot->eType = FTSQUERY_NOT;
-        pNot->pRight = p;
-        if( pNotBranch ){
-          pNot->pLeft = pNotBranch;
-        }
-        pNotBranch = pNot;
-        p = pPrev;
-      }else{
-        int eType = p->eType;
-        assert( eType!=FTSQUERY_PHRASE || !p->pPhrase->isNot );
-        isPhrase = (eType==FTSQUERY_PHRASE || p->pLeft);
-
-        /* The isRequirePhrase variable is set to true if a phrase or
-        ** an expression contained in parenthesis is required. If a
-        ** binary operator (AND, OR, NOT or NEAR) is encounted when
-        ** isRequirePhrase is set, this is a syntax error.
-        */
-        if( !isPhrase && isRequirePhrase ){
-          sqlite3Fts3ExprFree(p);
-          rc = SQLITE_ERROR;
-          goto exprparse_out;
-        }
-  
-        if( isPhrase && !isRequirePhrase ){
-          /* Insert an implicit AND operator. */
-          Fts3Expr *pAnd;
-          assert( pRet && pPrev );
-          pAnd = fts3MallocZero(sizeof(Fts3Expr));
-          if( !pAnd ){
+        if( !sqlite3_fts3_enable_parentheses 
+            && p->eType==FTSQUERY_PHRASE && pParse->isNot 
+        ){
+          /* Create an implicit NOT operator. */
+          Fts3Expr *pNot = fts3MallocZero(sizeof(Fts3Expr));
+          if( !pNot ){
             sqlite3Fts3ExprFree(p);
             rc = SQLITE_NOMEM;
             goto exprparse_out;
           }
-          pAnd->eType = FTSQUERY_AND;
-          insertBinaryOperator(&pRet, pPrev, pAnd);
-          pPrev = pAnd;
-        }
+          pNot->eType = FTSQUERY_NOT;
+          pNot->pRight = p;
+          p->pParent = pNot;
+          if( pNotBranch ){
+            pNot->pLeft = pNotBranch;
+            pNotBranch->pParent = pNot;
+          }
+          pNotBranch = pNot;
+          p = pPrev;
+        }else{
+          int eType = p->eType;
+          isPhrase = (eType==FTSQUERY_PHRASE || p->pLeft);
 
-        /* This test catches attempts to make either operand of a NEAR
-        ** operator something other than a phrase. For example, either of
-        ** the following:
-        **
-        **    (bracketed expression) NEAR phrase
-        **    phrase NEAR (bracketed expression)
-        **
-        ** Return an error in either case.
-        */
-        if( pPrev && (
+          /* The isRequirePhrase variable is set to true if a phrase or
+          ** an expression contained in parenthesis is required. If a
+          ** binary operator (AND, OR, NOT or NEAR) is encounted when
+          ** isRequirePhrase is set, this is a syntax error.
+          */
+          if( !isPhrase && isRequirePhrase ){
+            sqlite3Fts3ExprFree(p);
+            rc = SQLITE_ERROR;
+            goto exprparse_out;
+          }
+
+          if( isPhrase && !isRequirePhrase ){
+            /* Insert an implicit AND operator. */
+            Fts3Expr *pAnd;
+            assert( pRet && pPrev );
+            pAnd = fts3MallocZero(sizeof(Fts3Expr));
+            if( !pAnd ){
+              sqlite3Fts3ExprFree(p);
+              rc = SQLITE_NOMEM;
+              goto exprparse_out;
+            }
+            pAnd->eType = FTSQUERY_AND;
+            insertBinaryOperator(&pRet, pPrev, pAnd);
+            pPrev = pAnd;
+          }
+
+          /* This test catches attempts to make either operand of a NEAR
+           ** operator something other than a phrase. For example, either of
+           ** the following:
+           **
+           **    (bracketed expression) NEAR phrase
+           **    phrase NEAR (bracketed expression)
+           **
+           ** Return an error in either case.
+           */
+          if( pPrev && (
             (eType==FTSQUERY_NEAR && !isPhrase && pPrev->eType!=FTSQUERY_PHRASE)
          || (eType!=FTSQUERY_PHRASE && isPhrase && pPrev->eType==FTSQUERY_NEAR)
-        )){
-          sqlite3Fts3ExprFree(p);
-          rc = SQLITE_ERROR;
-          goto exprparse_out;
+          )){
+            sqlite3Fts3ExprFree(p);
+            rc = SQLITE_ERROR;
+            goto exprparse_out;
+          }
+
+          if( isPhrase ){
+            if( pRet ){
+              assert( pPrev && pPrev->pLeft && pPrev->pRight==0 );
+              pPrev->pRight = p;
+              p->pParent = pPrev;
+            }else{
+              pRet = p;
+            }
+          }else{
+            insertBinaryOperator(&pRet, pPrev, p);
+          }
+          isRequirePhrase = !isPhrase;
         }
-  
-        if( isPhrase ){
-          if( pRet ){
-            assert( pPrev && pPrev->pLeft && pPrev->pRight==0 );
-            pPrev->pRight = p;
-            p->pParent = pPrev;
-          }else{
-            pRet = p;
-          }
-        }else{
-          insertBinaryOperator(&pRet, pPrev, p);
-        }
-        isRequirePhrase = !isPhrase;
+        pPrev = p;
       }
       assert( nByte>0 );
     }
     assert( rc!=SQLITE_OK || (nByte>0 && nByte<=nIn) );
     nIn -= nByte;
     zIn += nByte;
-    pPrev = p;
   }
 
   if( rc==SQLITE_DONE && pRet && isRequirePhrase ){
     rc = SQLITE_ERROR;
   }
 
   if( rc==SQLITE_DONE ){
     rc = SQLITE_OK;
     if( !sqlite3_fts3_enable_parentheses && pNotBranch ){
       if( !pRet ){
         rc = SQLITE_ERROR;
       }else{
         Fts3Expr *pIter = pNotBranch;
         while( pIter->pLeft ){
           pIter = pIter->pLeft;
         }
         pIter->pLeft = pRet;
+        pRet->pParent = pIter;
         pRet = pNotBranch;
       }
     }
   }
   *pnConsumed = n - nIn;
 
 exprparse_out:
   if( rc!=SQLITE_OK ){
     sqlite3Fts3ExprFree(pRet);
     sqlite3Fts3ExprFree(pNotBranch);
     pRet = 0;
   }
   *ppExpr = pRet;
   return rc;
 }
 
 /*
+** Return SQLITE_ERROR if the maximum depth of the expression tree passed 
+** as the only argument is more than nMaxDepth.
+*/
+static int fts3ExprCheckDepth(Fts3Expr *p, int nMaxDepth){
+  int rc = SQLITE_OK;
+  if( p ){
+    if( nMaxDepth<0 ){ 
+      rc = SQLITE_TOOBIG;
+    }else{
+      rc = fts3ExprCheckDepth(p->pLeft, nMaxDepth-1);
+      if( rc==SQLITE_OK ){
+        rc = fts3ExprCheckDepth(p->pRight, nMaxDepth-1);
+      }
+    }
+  }
+  return rc;
+}
+
+/*
+** This function attempts to transform the expression tree at (*pp) to
+** an equivalent but more balanced form. The tree is modified in place.
+** If successful, SQLITE_OK is returned and (*pp) set to point to the 
+** new root expression node. 
+**
+** nMaxDepth is the maximum allowable depth of the balanced sub-tree.
+**
+** Otherwise, if an error occurs, an SQLite error code is returned and 
+** expression (*pp) freed.
+*/
+static int fts3ExprBalance(Fts3Expr **pp, int nMaxDepth){
+  int rc = SQLITE_OK;             /* Return code */
+  Fts3Expr *pRoot = *pp;          /* Initial root node */
+  Fts3Expr *pFree = 0;            /* List of free nodes. Linked by pParent. */
+  int eType = pRoot->eType;       /* Type of node in this tree */
+
+  if( nMaxDepth==0 ){
+    rc = SQLITE_ERROR;
+  }
+
+  if( rc==SQLITE_OK && (eType==FTSQUERY_AND || eType==FTSQUERY_OR) ){
+    Fts3Expr **apLeaf;
+    apLeaf = (Fts3Expr **)sqlite3_malloc(sizeof(Fts3Expr *) * nMaxDepth);
+    if( 0==apLeaf ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memset(apLeaf, 0, sizeof(Fts3Expr *) * nMaxDepth);
+    }
+
+    if( rc==SQLITE_OK ){
+      int i;
+      Fts3Expr *p;
+
+      /* Set $p to point to the left-most leaf in the tree of eType nodes. */
+      for(p=pRoot; p->eType==eType; p=p->pLeft){
+        assert( p->pParent==0 || p->pParent->pLeft==p );
+        assert( p->pLeft && p->pRight );
+      }
+
+      /* This loop runs once for each leaf in the tree of eType nodes. */
+      while( 1 ){
+        int iLvl;
+        Fts3Expr *pParent = p->pParent;     /* Current parent of p */
+
+        assert( pParent==0 || pParent->pLeft==p );
+        p->pParent = 0;
+        if( pParent ){
+          pParent->pLeft = 0;
+        }else{
+          pRoot = 0;
+        }
+        rc = fts3ExprBalance(&p, nMaxDepth-1);
+        if( rc!=SQLITE_OK ) break;
+
+        for(iLvl=0; p && iLvl<nMaxDepth; iLvl++){
+          if( apLeaf[iLvl]==0 ){
+            apLeaf[iLvl] = p;
+            p = 0;
+          }else{
+            assert( pFree );
+            pFree->pLeft = apLeaf[iLvl];
+            pFree->pRight = p;
+            pFree->pLeft->pParent = pFree;
+            pFree->pRight->pParent = pFree;
+
+            p = pFree;
+            pFree = pFree->pParent;
+            p->pParent = 0;
+            apLeaf[iLvl] = 0;
+          }
+        }
+        if( p ){
+          sqlite3Fts3ExprFree(p);
+          rc = SQLITE_TOOBIG;
+          break;
+        }
+
+        /* If that was the last leaf node, break out of the loop */
+        if( pParent==0 ) break;
+
+        /* Set $p to point to the next leaf in the tree of eType nodes */
+        for(p=pParent->pRight; p->eType==eType; p=p->pLeft);
+
+        /* Remove pParent from the original tree. */
+        assert( pParent->pParent==0 || pParent->pParent->pLeft==pParent );
+        pParent->pRight->pParent = pParent->pParent;
+        if( pParent->pParent ){
+          pParent->pParent->pLeft = pParent->pRight;
+        }else{
+          assert( pParent==pRoot );
+          pRoot = pParent->pRight;
+        }
+
+        /* Link pParent into the free node list. It will be used as an
+        ** internal node of the new tree.  */
+        pParent->pParent = pFree;
+        pFree = pParent;
+      }
+
+      if( rc==SQLITE_OK ){
+        p = 0;
+        for(i=0; i<nMaxDepth; i++){
+          if( apLeaf[i] ){
+            if( p==0 ){
+              p = apLeaf[i];
+              p->pParent = 0;
+            }else{
+              assert( pFree!=0 );
+              pFree->pRight = p;
+              pFree->pLeft = apLeaf[i];
+              pFree->pLeft->pParent = pFree;
+              pFree->pRight->pParent = pFree;
+
+              p = pFree;
+              pFree = pFree->pParent;
+              p->pParent = 0;
+            }
+          }
+        }
+        pRoot = p;
+      }else{
+        /* An error occurred. Delete the contents of the apLeaf[] array 
+        ** and pFree list. Everything else is cleaned up by the call to
+        ** sqlite3Fts3ExprFree(pRoot) below.  */
+        Fts3Expr *pDel;
+        for(i=0; i<nMaxDepth; i++){
+          sqlite3Fts3ExprFree(apLeaf[i]);
+        }
+        while( (pDel=pFree)!=0 ){
+          pFree = pDel->pParent;
+          sqlite3_free(pDel);
+        }
+      }
+
+      assert( pFree==0 );
+      sqlite3_free( apLeaf );
+    }
+  }
+
+  if( rc!=SQLITE_OK ){
+    sqlite3Fts3ExprFree(pRoot);
+    pRoot = 0;
+  }
+  *pp = pRoot;
+  return rc;
+}
+
+/*
+** This function is similar to sqlite3Fts3ExprParse(), with the following
+** differences:
+**
+**   1. It does not do expression rebalancing.
+**   2. It does not check that the expression does not exceed the 
+**      maximum allowable depth.
+**   3. Even if it fails, *ppExpr may still be set to point to an 
+**      expression tree. It should be deleted using sqlite3Fts3ExprFree()
+**      in this case.
+*/
+static int fts3ExprParseUnbalanced(
+  sqlite3_tokenizer *pTokenizer,      /* Tokenizer module */
+  int iLangid,                        /* Language id for tokenizer */
+  char **azCol,                       /* Array of column names for fts3 table */
+  int bFts4,                          /* True to allow FTS4-only syntax */
+  int nCol,                           /* Number of entries in azCol[] */
+  int iDefaultCol,                    /* Default column to query */
+  const char *z, int n,               /* Text of MATCH query */
+  Fts3Expr **ppExpr                   /* OUT: Parsed query structure */
+){
+  int nParsed;
+  int rc;
+  ParseContext sParse;
+
+  memset(&sParse, 0, sizeof(ParseContext));
+  sParse.pTokenizer = pTokenizer;
+  sParse.iLangid = iLangid;
+  sParse.azCol = (const char **)azCol;
+  sParse.nCol = nCol;
+  sParse.iDefaultCol = iDefaultCol;
+  sParse.bFts4 = bFts4;
+  if( z==0 ){
+    *ppExpr = 0;
+    return SQLITE_OK;
+  }
+  if( n<0 ){
+    n = (int)strlen(z);
+  }
+  rc = fts3ExprParse(&sParse, z, n, ppExpr, &nParsed);
+  assert( rc==SQLITE_OK || *ppExpr==0 );
+
+  /* Check for mismatched parenthesis */
+  if( rc==SQLITE_OK && sParse.nNest ){
+    rc = SQLITE_ERROR;
+  }
+  
+  return rc;
+}
+
+/*
 ** Parameters z and n contain a pointer to and length of a buffer containing
 ** an fts3 query expression, respectively. This function attempts to parse the
 ** query expression and create a tree of Fts3Expr structures representing the
 ** parsed expression. If successful, *ppExpr is set to point to the head
 ** of the parsed expression tree and SQLITE_OK is returned. If an error
 ** occurs, either SQLITE_NOMEM (out-of-memory error) or SQLITE_ERROR (parse
 ** error) is returned and *ppExpr is set to 0.
 **
 ** If parameter n is a negative number, then z is assumed to point to a
 ** nul-terminated string and the length is determined using strlen().
 **
 ** The first parameter, pTokenizer, is passed the fts3 tokenizer module to
 ** use to normalize query tokens while parsing the expression. The azCol[]
 ** array, which is assumed to contain nCol entries, should contain the names
 ** of each column in the target fts3 table, in order from left to right. 
 ** Column names must be nul-terminated strings.
 **
 ** The iDefaultCol parameter should be passed the index of the table column
 ** that appears on the left-hand-side of the MATCH operator (the default
 ** column to match against for tokens for which a column name is not explicitly
 ** specified as part of the query string), or -1 if tokens may by default
 ** match any table column.
 */
 int sqlite3Fts3ExprParse(
   sqlite3_tokenizer *pTokenizer,      /* Tokenizer module */
+  int iLangid,                        /* Language id for tokenizer */
   char **azCol,                       /* Array of column names for fts3 table */
+  int bFts4,                          /* True to allow FTS4-only syntax */
   int nCol,                           /* Number of entries in azCol[] */
   int iDefaultCol,                    /* Default column to query */
   const char *z, int n,               /* Text of MATCH query */
-  Fts3Expr **ppExpr                   /* OUT: Parsed query structure */
+  Fts3Expr **ppExpr,                  /* OUT: Parsed query structure */
+  char **pzErr                        /* OUT: Error message (sqlite3_malloc) */
 ){
-  int nParsed;
-  int rc;
-  ParseContext sParse;
-  sParse.pTokenizer = pTokenizer;
-  sParse.azCol = (const char **)azCol;
-  sParse.nCol = nCol;
-  sParse.iDefaultCol = iDefaultCol;
-  sParse.nNest = 0;
-  if( z==0 ){
-    *ppExpr = 0;
-    return SQLITE_OK;
+  int rc = fts3ExprParseUnbalanced(
+      pTokenizer, iLangid, azCol, bFts4, nCol, iDefaultCol, z, n, ppExpr
+  );
+  
+  /* Rebalance the expression. And check that its depth does not exceed
+  ** SQLITE_FTS3_MAX_EXPR_DEPTH.  */
+  if( rc==SQLITE_OK && *ppExpr ){
+    rc = fts3ExprBalance(ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
+    if( rc==SQLITE_OK ){
+      rc = fts3ExprCheckDepth(*ppExpr, SQLITE_FTS3_MAX_EXPR_DEPTH);
+    }
   }
-  if( n<0 ){
-    n = (int)strlen(z);
-  }
-  rc = fts3ExprParse(&sParse, z, n, ppExpr, &nParsed);
 
-  /* Check for mismatched parenthesis */
-  if( rc==SQLITE_OK && sParse.nNest ){
-    rc = SQLITE_ERROR;
+  if( rc!=SQLITE_OK ){
     sqlite3Fts3ExprFree(*ppExpr);
     *ppExpr = 0;
+    if( rc==SQLITE_TOOBIG ){
+      *pzErr = sqlite3_mprintf(
+          "FTS expression tree is too large (maximum depth %d)", 
+          SQLITE_FTS3_MAX_EXPR_DEPTH
+      );
+      rc = SQLITE_ERROR;
+    }else if( rc==SQLITE_ERROR ){
+      *pzErr = sqlite3_mprintf("malformed MATCH expression: [%s]", z);
+    }
   }
 
   return rc;
 }
 
 /*
+** Free a single node of an expression tree.
+*/
+static void fts3FreeExprNode(Fts3Expr *p){
+  assert( p->eType==FTSQUERY_PHRASE || p->pPhrase==0 );
+  sqlite3Fts3EvalPhraseCleanup(p->pPhrase);
+  sqlite3_free(p->aMI);
+  sqlite3_free(p);
+}
+
+/*
 ** Free a parsed fts3 query expression allocated by sqlite3Fts3ExprParse().
+**
+** This function would be simpler if it recursively called itself. But
+** that would mean passing a sufficiently large expression to ExprParse()
+** could cause a stack overflow.
 */
-void sqlite3Fts3ExprFree(Fts3Expr *p){
-  if( p ){
-    sqlite3Fts3ExprFree(p->pLeft);
-    sqlite3Fts3ExprFree(p->pRight);
-    sqlite3_free(p->aDoclist);
-    sqlite3_free(p);
+void sqlite3Fts3ExprFree(Fts3Expr *pDel){
+  Fts3Expr *p;
+  assert( pDel==0 || pDel->pParent==0 );
+  for(p=pDel; p && (p->pLeft||p->pRight); p=(p->pLeft ? p->pLeft : p->pRight)){
+    assert( p->pParent==0 || p==p->pParent->pRight || p==p->pParent->pLeft );
+  }
+  while( p ){
+    Fts3Expr *pParent = p->pParent;
+    fts3FreeExprNode(p);
+    if( pParent && p==pParent->pLeft && pParent->pRight ){
+      p = pParent->pRight;
+      while( p && (p->pLeft || p->pRight) ){
+        assert( p==p->pParent->pRight || p==p->pParent->pLeft );
+        p = (p->pLeft ? p->pLeft : p->pRight);
+      }
+    }else{
+      p = pParent;
+    }
   }
 }
 
 /****************************************************************************
 *****************************************************************************
 ** Everything after this point is just test code.
 */
 
 #ifdef SQLITE_TEST
 
@@ skipping 31 matching lines @@
 ** Return a pointer to a buffer containing a text representation of the
 ** expression passed as the first argument. The buffer is obtained from
 ** sqlite3_malloc(). It is the responsibility of the caller to use 
 ** sqlite3_free() to release the memory. If an OOM condition is encountered,
 ** NULL is returned.
 **
 ** If the second argument is not NULL, then its contents are prepended to 
 ** the returned expression text and then freed using sqlite3_free().
 */
 static char *exprToString(Fts3Expr *pExpr, char *zBuf){
+  if( pExpr==0 ){
+    return sqlite3_mprintf("");
+  }
   switch( pExpr->eType ){
     case FTSQUERY_PHRASE: {
       Fts3Phrase *pPhrase = pExpr->pPhrase;
       int i;
       zBuf = sqlite3_mprintf(
-          "%zPHRASE %d %d", zBuf, pPhrase->iColumn, pPhrase->isNot);
+          "%zPHRASE %d 0", zBuf, pPhrase->iColumn);
       for(i=0; zBuf && i<pPhrase->nToken; i++){
         zBuf = sqlite3_mprintf("%z %.*s%s", zBuf, 
             pPhrase->aToken[i].n, pPhrase->aToken[i].z,
             (pPhrase->aToken[i].isPrefix?"+":"")
         );
       }
       return zBuf;
     }
 
     case FTSQUERY_NEAR:
@@ skipping 81 matching lines @@
   nCol = argc-2;
   azCol = (char **)sqlite3_malloc(nCol*sizeof(char *));
   if( !azCol ){
     sqlite3_result_error_nomem(context);
     goto exprtest_out;
   }
   for(ii=0; ii<nCol; ii++){
     azCol[ii] = (char *)sqlite3_value_text(argv[ii+2]);
   }
 
-  rc = sqlite3Fts3ExprParse(
-      pTokenizer, azCol, nCol, nCol, zExpr, nExpr, &pExpr
-  );
+  if( sqlite3_user_data(context) ){
+    char *zDummy = 0;
+    rc = sqlite3Fts3ExprParse(
+        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr, &zDummy
+    );
+    assert( rc==SQLITE_OK || pExpr==0 );
+    sqlite3_free(zDummy);
+  }else{
+    rc = fts3ExprParseUnbalanced(
+        pTokenizer, 0, azCol, 0, nCol, nCol, zExpr, nExpr, &pExpr
+    );
+  }
+
   if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM ){
+    sqlite3Fts3ExprFree(pExpr);
     sqlite3_result_error(context, "Error parsing expression", -1);
   }else if( rc==SQLITE_NOMEM || !(zBuf = exprToString(pExpr, 0)) ){
     sqlite3_result_error_nomem(context);
   }else{
     sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
     sqlite3_free(zBuf);
   }
 
   sqlite3Fts3ExprFree(pExpr);
 
 exprtest_out:
   if( pModule && pTokenizer ){
     rc = pModule->xDestroy(pTokenizer);
   }
   sqlite3_free(azCol);
 }
 
 /*
 ** Register the query expression parser test function fts3_exprtest() 
 ** with database connection db. 
 */
 int sqlite3Fts3ExprInitTestInterface(sqlite3* db){
-  return sqlite3_create_function(
+  int rc = sqlite3_create_function(
       db, "fts3_exprtest", -1, SQLITE_UTF8, 0, fts3ExprTest, 0, 0
   );
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "fts3_exprtest_rebalance", 
+        -1, SQLITE_UTF8, (void *)1, fts3ExprTest, 0, 0
+    );
+  }
+  return rc;
 }
 
 #endif
 #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */