/*
** 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 1.91 2009/07/02 07:47:33 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;
VVA_ONLY( int rc; )
if( !zSql ){
return SQLITE_NOMEM;
}
if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){
return sqlite3_errcode(db);
}
VVA_ONLY( rc = ) sqlite3_step(pStmt);
assert( rc!=SQLITE_ROW );
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 */
int saved_nChange; /* Saved value of db->nChange */
int saved_nTotalChange; /* Saved value of db->nTotalChange */
Db *pDb = 0; /* Database to detach at end of vacuum */
int isMemDb; /* True if vacuuming a :memory: database */
int nRes;
if( !db->autoCommit ){
sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
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;
db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks;
db->flags &= ~SQLITE_ForeignKeys;
pMain = db->aDb[0].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.
*/
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;
/* 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 = sqlite3BtreeGetReserve(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
if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
|| (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
|| NEVER(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 main.xxx;" to copy
** the contents to the temporary database.
*/
rc = execExecSql(db,
"SELECT 'INSERT INTO vacuum_db.' || quote(name) "
"|| ' SELECT * FROM main.' || quote(name) || ';'"
"FROM main.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 main.' || 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 main.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.
*/
{
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 */
};
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->flags = saved_flags;
db->nChange = saved_nChange;
db->nTotalChange = saved_nTotalChange;
/* 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 */