[sql] Import reference version of SQLite 3.17..

third_party/sqlite/sqlite-src-3170000/src/vacuum.c

+/*
+** 2003 April 6
+**
+** 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 file contains code used to implement the VACUUM command.
+**
+** Most of the code in this file may be omitted by defining the
+** SQLITE_OMIT_VACUUM macro.
+*/
+#include "sqliteInt.h"
+#include "vdbeInt.h"
+
+#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
+
+/*
+** Execute zSql on database db.
+**
+** If zSql returns rows, then each row will have exactly one
+** column.  (This will only happen if zSql begins with "SELECT".)
+** Take each row of result and call execSql() again recursively.
+**
+** The execSqlF() routine does the same thing, except it accepts
+** a format string as its third argument
+*/
+static int execSql(sqlite3 *db, char **pzErrMsg, const char *zSql){
+  sqlite3_stmt *pStmt;
+  int rc;
+
+  /* printf("SQL: [%s]\n", zSql); fflush(stdout); */
+  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+  if( rc!=SQLITE_OK ) return rc;
+  while( SQLITE_ROW==(rc = sqlite3_step(pStmt)) ){
+    const char *zSubSql = (const char*)sqlite3_column_text(pStmt,0);
+    assert( sqlite3_strnicmp(zSql,"SELECT",6)==0 );
+    if( zSubSql ){
+      assert( zSubSql[0]!='S' );
+      rc = execSql(db, pzErrMsg, zSubSql);
+      if( rc!=SQLITE_OK ) break;
+    }
+  }
+  assert( rc!=SQLITE_ROW );
+  if( rc==SQLITE_DONE ) rc = SQLITE_OK;
+  if( rc ){
+    sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db));
+  }
+  (void)sqlite3_finalize(pStmt);
+  return rc;
+}
+static int execSqlF(sqlite3 *db, char **pzErrMsg, const char *zSql, ...){
+  char *z;
+  va_list ap;
+  int rc;
+  va_start(ap, zSql);
+  z = sqlite3VMPrintf(db, zSql, ap);
+  va_end(ap);
+  if( z==0 ) return SQLITE_NOMEM;
+  rc = execSql(db, pzErrMsg, z);
+  sqlite3DbFree(db, z);
+  return rc;
+}
+
+/*
+** The VACUUM command is used to clean up the database,
+** collapse free space, etc.  It is modelled after the VACUUM command
+** in PostgreSQL.  The VACUUM command works as follows:
+**
+**   (1)  Create a new transient database file
+**   (2)  Copy all content from the database being vacuumed into
+**        the new transient database file
+**   (3)  Copy content from the transient database back into the
+**        original database.
+**
+** The transient database requires temporary disk space approximately
+** equal to the size of the original database.  The copy operation of
+** step (3) requires additional temporary disk space approximately equal
+** to the size of the original database for the rollback journal.
+** Hence, temporary disk space that is approximately 2x the size of the
+** original database is required.  Every page of the database is written
+** approximately 3 times:  Once for step (2) and twice for step (3).
+** Two writes per page are required in step (3) because the original
+** database content must be written into the rollback journal prior to
+** overwriting the database with the vacuumed content.
+**
+** Only 1x temporary space and only 1x writes would be required if
+** the copy of step (3) were replaced by deleting the original database
+** and renaming the transient database as the original.  But that will
+** not work if other processes are attached to the original database.
+** And a power loss in between deleting the original and renaming the
+** transient would cause the database file to appear to be deleted
+** following reboot.
+*/
+void sqlite3Vacuum(Parse *pParse, Token *pNm){
+  Vdbe *v = sqlite3GetVdbe(pParse);
+  int iDb = pNm ? sqlite3TwoPartName(pParse, pNm, pNm, &pNm) : 0;
+  if( v && (iDb>=2 || iDb==0) ){
+    sqlite3VdbeAddOp1(v, OP_Vacuum, iDb);
+    sqlite3VdbeUsesBtree(v, iDb);
+  }
+  return;
+}
+
+/*
+** This routine implements the OP_Vacuum opcode of the VDBE.
+*/
+int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db, int iDb){
+  int rc = SQLITE_OK;     /* Return code from service routines */
+  Btree *pMain;           /* The database being vacuumed */
+  Btree *pTemp;           /* The temporary database we vacuum into */
+  int saved_flags;        /* Saved value of the db->flags */
+  int saved_nChange;      /* Saved value of db->nChange */
+  int saved_nTotalChange; /* Saved value of db->nTotalChange */
+  u8 saved_mTrace;        /* Saved trace settings */
+  Db *pDb = 0;            /* Database to detach at end of vacuum */
+  int isMemDb;            /* True if vacuuming a :memory: database */
+  int nRes;               /* Bytes of reserved space at the end of each page */
+  int nDb;                /* Number of attached databases */
+  const char *zDbMain;    /* Schema name of database to vacuum */
+
+  if( !db->autoCommit ){
+    sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
+    return SQLITE_ERROR;
+  }
+  if( db->nVdbeActive>1 ){
+    sqlite3SetString(pzErrMsg, db,"cannot VACUUM - SQL statements in progress");
+    return SQLITE_ERROR;
+  }
+
+  /* Save the current value of the database flags so that it can be 
+  ** restored before returning. Then set the writable-schema flag, and
+  ** disable CHECK and foreign key constraints.  */
+  saved_flags = db->flags;
+  saved_nChange = db->nChange;
+  saved_nTotalChange = db->nTotalChange;
+  saved_mTrace = db->mTrace;
+  db->flags |= (SQLITE_WriteSchema | SQLITE_IgnoreChecks
+                 | SQLITE_PreferBuiltin | SQLITE_Vacuum);
+  db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder | SQLITE_CountRows);
+  db->mTrace = 0;
+
+  zDbMain = db->aDb[iDb].zDbSName;
+  pMain = db->aDb[iDb].pBt;
+  isMemDb = sqlite3PagerIsMemdb(sqlite3BtreePager(pMain));
+
+  /* Attach the temporary database as 'vacuum_db'. The synchronous pragma
+  ** can be set to 'off' for this file, as it is not recovered if a crash
+  ** occurs anyway. The integrity of the database is maintained by a
+  ** (possibly synchronous) transaction opened on the main database before
+  ** sqlite3BtreeCopyFile() is called.
+  **
+  ** An optimisation would be to use a non-journaled pager.
+  ** (Later:) I tried setting "PRAGMA vacuum_db.journal_mode=OFF" but
+  ** that actually made the VACUUM run slower.  Very little journalling
+  ** actually occurs when doing a vacuum since the vacuum_db is initially
+  ** empty.  Only the journal header is written.  Apparently it takes more
+  ** time to parse and run the PRAGMA to turn journalling off than it does
+  ** to write the journal header file.
+  */
+  nDb = db->nDb;
+  rc = execSql(db, pzErrMsg, "ATTACH''AS vacuum_db");
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  assert( (db->nDb-1)==nDb );
+  pDb = &db->aDb[nDb];
+  assert( strcmp(pDb->zDbSName,"vacuum_db")==0 );
+  pTemp = pDb->pBt;
+
+  /* The call to execSql() to attach the temp database has left the file
+  ** locked (as there was more than one active statement when the transaction
+  ** to read the schema was concluded. Unlock it here so that this doesn't
+  ** cause problems for the call to BtreeSetPageSize() below.  */
+  sqlite3BtreeCommit(pTemp);
+
+  nRes = sqlite3BtreeGetOptimalReserve(pMain);
+
+  /* A VACUUM cannot change the pagesize of an encrypted database. */
+#ifdef SQLITE_HAS_CODEC
+  if( db->nextPagesize ){
+    extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*);
+    int nKey;
+    char *zKey;
+    sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey);
+    if( nKey ) db->nextPagesize = 0;
+  }
+#endif
+
+  sqlite3BtreeSetCacheSize(pTemp, db->aDb[iDb].pSchema->cache_size);
+  sqlite3BtreeSetSpillSize(pTemp, sqlite3BtreeSetSpillSize(pMain,0));
+  sqlite3BtreeSetPagerFlags(pTemp, PAGER_SYNCHRONOUS_OFF|PAGER_CACHESPILL);
+
+  /* Begin a transaction and take an exclusive lock on the main database
+  ** file. This is done before the sqlite3BtreeGetPageSize(pMain) call below,
+  ** to ensure that we do not try to change the page-size on a WAL database.
+  */
+  rc = execSql(db, pzErrMsg, "BEGIN");
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  rc = sqlite3BtreeBeginTrans(pMain, 2);
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+  /* Do not attempt to change the page size for a WAL database */
+  if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain))
+                                               ==PAGER_JOURNALMODE_WAL ){
+    db->nextPagesize = 0;
+  }
+
+  if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
+   || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
+   || NEVER(db->mallocFailed)
+  ){
+    rc = SQLITE_NOMEM_BKPT;
+    goto end_of_vacuum;
+  }
+
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac :
+                                           sqlite3BtreeGetAutoVacuum(pMain));
+#endif
+
+  /* Query the schema of the main database. Create a mirror schema
+  ** in the temporary database.
+  */
+  db->init.iDb = nDb; /* force new CREATE statements into vacuum_db */
+  rc = execSqlF(db, pzErrMsg,
+      "SELECT sql FROM \"%w\".sqlite_master"
+      " WHERE type='table'AND name<>'sqlite_sequence'"
+      " AND coalesce(rootpage,1)>0",
+      zDbMain
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  rc = execSqlF(db, pzErrMsg,
+      "SELECT sql FROM \"%w\".sqlite_master"
+      " WHERE type='index' AND length(sql)>10",
+      zDbMain
+  );
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+  db->init.iDb = 0;
+
+  /* Loop through the tables in the main database. For each, do
+  ** an "INSERT INTO vacuum_db.xxx SELECT * FROM main.xxx;" to copy
+  ** the contents to the temporary database.
+  */
+  rc = execSqlF(db, pzErrMsg,
+      "SELECT'INSERT INTO vacuum_db.'||quote(name)"
+      "||' SELECT*FROM\"%w\".'||quote(name)"
+      "FROM vacuum_db.sqlite_master "
+      "WHERE type='table'AND coalesce(rootpage,1)>0",
+      zDbMain
+  );
+  assert( (db->flags & SQLITE_Vacuum)!=0 );
+  db->flags &= ~SQLITE_Vacuum;
+  if( rc!=SQLITE_OK ) goto end_of_vacuum;
+
+  /* Copy the triggers, views, and virtual tables from the main database
+  ** over to the temporary database.  None of these objects has any
+  ** associated storage, so all we have to do is copy their entries
+  ** from the SQLITE_MASTER table.
+  */
+  rc = execSqlF(db, pzErrMsg,
+      "INSERT INTO vacuum_db.sqlite_master"
+      " SELECT*FROM \"%w\".sqlite_master"
+      " WHERE type IN('view','trigger')"
+      " OR(type='table'AND rootpage=0)",
+      zDbMain
+  );
+  if( rc ) goto end_of_vacuum;
+
+  /* At this point, there is a write transaction open on both the 
+  ** vacuum database and the main database. Assuming no error occurs,
+  ** both transactions are closed by this block - the main database
+  ** transaction by sqlite3BtreeCopyFile() and the other by an explicit
+  ** call to sqlite3BtreeCommit().
+  */
+  {
+    u32 meta;
+    int i;
+
+    /* This array determines which meta meta values are preserved in the
+    ** vacuum.  Even entries are the meta value number and odd entries
+    ** are an increment to apply to the meta value after the vacuum.
+    ** The increment is used to increase the schema cookie so that other
+    ** connections to the same database will know to reread the schema.
+    */
+    static const unsigned char aCopy[] = {
+       BTREE_SCHEMA_VERSION,     1,  /* Add one to the old schema cookie */
+       BTREE_DEFAULT_CACHE_SIZE, 0,  /* Preserve the default page cache size */
+       BTREE_TEXT_ENCODING,      0,  /* Preserve the text encoding */
+       BTREE_USER_VERSION,       0,  /* Preserve the user version */
+       BTREE_APPLICATION_ID,     0,  /* Preserve the application id */
+    };
+
+    assert( 1==sqlite3BtreeIsInTrans(pTemp) );
+    assert( 1==sqlite3BtreeIsInTrans(pMain) );
+
+    /* Copy Btree meta values */
+    for(i=0; i<ArraySize(aCopy); i+=2){
+      /* GetMeta() and UpdateMeta() cannot fail in this context because
+      ** we already have page 1 loaded into cache and marked dirty. */
+      sqlite3BtreeGetMeta(pMain, aCopy[i], &meta);
+      rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]);
+      if( NEVER(rc!=SQLITE_OK) ) goto end_of_vacuum;
+    }
+
+    rc = sqlite3BtreeCopyFile(pMain, pTemp);
+    if( rc!=SQLITE_OK ) goto end_of_vacuum;
+    rc = sqlite3BtreeCommit(pTemp);
+    if( rc!=SQLITE_OK ) goto end_of_vacuum;
+#ifndef SQLITE_OMIT_AUTOVACUUM
+    sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp));
+#endif
+  }
+
+  assert( rc==SQLITE_OK );
+  rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1);
+
+end_of_vacuum:
+  /* Restore the original value of db->flags */
+  db->init.iDb = 0;
+  db->flags = saved_flags;
+  db->nChange = saved_nChange;
+  db->nTotalChange = saved_nTotalChange;
+  db->mTrace = saved_mTrace;
+  sqlite3BtreeSetPageSize(pMain, -1, -1, 1);
+
+  /* Currently there is an SQL level transaction open on the vacuum
+  ** database. No locks are held on any other files (since the main file
+  ** was committed at the btree level). So it safe to end the transaction
+  ** by manually setting the autoCommit flag to true and detaching the
+  ** vacuum database. The vacuum_db journal file is deleted when the pager
+  ** is closed by the DETACH.
+  */
+  db->autoCommit = 1;
+
+  if( pDb ){
+    sqlite3BtreeClose(pDb->pBt);
+    pDb->pBt = 0;
+    pDb->pSchema = 0;
+  }
+
+  /* This both clears the schemas and reduces the size of the db->aDb[]
+  ** array. */ 
+  sqlite3ResetAllSchemasOfConnection(db);
+
+  return rc;
+}
+
+#endif  /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */