vacuum.c.svn-base
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- /*
- ** 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.
- **
- ** $Id: vacuum.c,v 1.77 2008/03/20 11:04:21 danielk1977 Exp $
- */
- #include "sqliteInt.h"
- #include "vdbeInt.h"
- #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
- /*
- ** Execute zSql on database db. Return an error code.
- */
- static int execSql(sqlite3 *db, const char *zSql){
- sqlite3_stmt *pStmt;
- if( !zSql ){
- return SQLITE_NOMEM;
- }
- if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){
- return sqlite3_errcode(db);
- }
- while( SQLITE_ROW==sqlite3_step(pStmt) ){}
- return sqlite3_finalize(pStmt);
- }
- /*
- ** Execute zSql on database db. The statement returns exactly
- ** one column. Execute this as SQL on the same database.
- */
- static int execExecSql(sqlite3 *db, const char *zSql){
- sqlite3_stmt *pStmt;
- int rc;
- rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
- if( rc!=SQLITE_OK ) return rc;
- while( SQLITE_ROW==sqlite3_step(pStmt) ){
- rc = execSql(db, (char*)sqlite3_column_text(pStmt, 0));
- if( rc!=SQLITE_OK ){
- sqlite3_finalize(pStmt);
- return rc;
- }
- }
- return sqlite3_finalize(pStmt);
- }
- /*
- ** The non-standard VACUUM command is used to clean up the database,
- ** collapse free space, etc. It is modelled after the VACUUM command
- ** in PostgreSQL.
- **
- ** In version 1.0.x of SQLite, the VACUUM command would call
- ** gdbm_reorganize() on all the database tables. But beginning
- ** with 2.0.0, SQLite no longer uses GDBM so this command has
- ** become a no-op.
- */
- void sqlite3Vacuum(Parse *pParse){
- Vdbe *v = sqlite3GetVdbe(pParse);
- if( v ){
- sqlite3VdbeAddOp2(v, OP_Vacuum, 0, 0);
- }
- return;
- }
- /*
- ** This routine implements the OP_Vacuum opcode of the VDBE.
- */
- int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){
- int rc = SQLITE_OK; /* Return code from service routines */
- Btree *pMain; /* The database being vacuumed */
- Btree *pTemp; /* The temporary database we vacuum into */
- char *zSql = 0; /* SQL statements */
- int saved_flags; /* Saved value of the db->flags */
- Db *pDb = 0; /* Database to detach at end of vacuum */
- int nRes;
- /* Save the current value of the write-schema flag before setting it. */
- saved_flags = db->flags;
- db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks;
- if( !db->autoCommit ){
- sqlite3SetString(pzErrMsg, "cannot VACUUM from within a transaction",
- (char*)0);
- rc = SQLITE_ERROR;
- goto end_of_vacuum;
- }
- pMain = db->aDb[0].pBt;
- /* 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.
- */
- zSql = "ATTACH '' AS vacuum_db;";
- rc = execSql(db, zSql);
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- pDb = &db->aDb[db->nDb-1];
- assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 );
- pTemp = db->aDb[db->nDb-1].pBt;
- nRes = sqlite3BtreeGetReserve(pMain);
- if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes)
- || sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes)
- || db->mallocFailed
- ){
- rc = SQLITE_NOMEM;
- goto end_of_vacuum;
- }
- rc = execSql(db, "PRAGMA vacuum_db.synchronous=OFF");
- if( rc!=SQLITE_OK ){
- goto end_of_vacuum;
- }
- #ifndef SQLITE_OMIT_AUTOVACUUM
- sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac :
- sqlite3BtreeGetAutoVacuum(pMain));
- #endif
- /* Begin a transaction */
- rc = execSql(db, "BEGIN EXCLUSIVE;");
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- /* Query the schema of the main database. Create a mirror schema
- ** in the temporary database.
- */
- rc = execExecSql(db,
- "SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14) "
- " FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'"
- " AND rootpage>0"
- );
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- rc = execExecSql(db,
- "SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14)"
- " FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %' ");
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- rc = execExecSql(db,
- "SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21) "
- " FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'");
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- /* Loop through the tables in the main database. For each, do
- ** an "INSERT INTO vacuum_db.xxx SELECT * FROM xxx;" to copy
- ** the contents to the temporary database.
- */
- rc = execExecSql(db,
- "SELECT 'INSERT INTO vacuum_db.' || quote(name) "
- "|| ' SELECT * FROM ' || quote(name) || ';'"
- "FROM sqlite_master "
- "WHERE type = 'table' AND name!='sqlite_sequence' "
- " AND rootpage>0"
- );
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- /* Copy over the sequence table
- */
- rc = execExecSql(db,
- "SELECT 'DELETE FROM vacuum_db.' || quote(name) || ';' "
- "FROM vacuum_db.sqlite_master WHERE name='sqlite_sequence' "
- );
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- rc = execExecSql(db,
- "SELECT 'INSERT INTO vacuum_db.' || quote(name) "
- "|| ' SELECT * FROM ' || quote(name) || ';' "
- "FROM vacuum_db.sqlite_master WHERE name=='sqlite_sequence';"
- );
- 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 = execSql(db,
- "INSERT INTO vacuum_db.sqlite_master "
- " SELECT type, name, tbl_name, rootpage, sql"
- " FROM sqlite_master"
- " WHERE type='view' OR type='trigger'"
- " OR (type='table' AND rootpage=0)"
- );
- if( rc ) goto end_of_vacuum;
- /* At this point, unless the main db was completely empty, there is now a
- ** transaction open on the vacuum database, but not on the main database.
- ** Open a btree level transaction on the main database. This allows a
- ** call to sqlite3BtreeCopyFile(). The main database btree level
- ** transaction is then committed, so the SQL level never knows it was
- ** opened for writing. This way, the SQL transaction used to create the
- ** temporary database never needs to be committed.
- */
- if( rc==SQLITE_OK ){
- 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[] = {
- 1, 1, /* Add one to the old schema cookie */
- 3, 0, /* Preserve the default page cache size */
- 5, 0, /* Preserve the default text encoding */
- 6, 0, /* Preserve the user version */
- };
- assert( 1==sqlite3BtreeIsInTrans(pTemp) );
- assert( 1==sqlite3BtreeIsInTrans(pMain) );
- /* Copy Btree meta values */
- for(i=0; i<sizeof(aCopy)/sizeof(aCopy[0]); i+=2){
- rc = sqlite3BtreeGetMeta(pMain, aCopy[i], &meta);
- if( rc!=SQLITE_OK ) goto end_of_vacuum;
- rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]);
- if( 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;
- rc = sqlite3BtreeCommit(pMain);
- }
- if( rc==SQLITE_OK ){
- rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes);
- }
- end_of_vacuum:
- /* Restore the original value of db->flags */
- db->flags = saved_flags;
- /* 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;
- }
- sqlite3ResetInternalSchema(db, 0);
- return rc;
- }
- #endif /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */