diff options
author | Hans-Christoph Steiner <hans@eds.org> | 2012-03-30 20:42:12 -0400 |
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committer | Hans-Christoph Steiner <hans@eds.org> | 2012-03-30 20:42:12 -0400 |
commit | 7bb481fda9ecb134804b49c2ce77ca28f7eea583 (patch) | |
tree | 31b520b9914d3e2453968abe375f2c102772c3dc /src/vacuum.c |
Imported Upstream version 2.0.3
Diffstat (limited to 'src/vacuum.c')
-rw-r--r-- | src/vacuum.c | 343 |
1 files changed, 343 insertions, 0 deletions
diff --git a/src/vacuum.c b/src/vacuum.c new file mode 100644 index 0000000..58a3c9d --- /dev/null +++ b/src/vacuum.c @@ -0,0 +1,343 @@ +/* +** 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) +/* +** Finalize a prepared statement. If there was an error, store the +** text of the error message in *pzErrMsg. Return the result code. +*/ +static int vacuumFinalize(sqlite3 *db, sqlite3_stmt *pStmt, char **pzErrMsg){ + int rc; + rc = sqlite3VdbeFinalize((Vdbe*)pStmt); + if( rc ){ + sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db)); + } + return rc; +} + +/* +** Execute zSql on database db. Return an error code. +*/ +static int execSql(sqlite3 *db, char **pzErrMsg, 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) ){ + sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db)); + return sqlite3_errcode(db); + } + VVA_ONLY( rc = ) sqlite3_step(pStmt); + assert( rc!=SQLITE_ROW || (db->flags&SQLITE_CountRows) ); + return vacuumFinalize(db, pStmt, pzErrMsg); +} + +/* +** Execute zSql on database db. The statement returns exactly +** one column. Execute this as SQL on the same database. +*/ +static int execExecSql(sqlite3 *db, char **pzErrMsg, 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, pzErrMsg, (char*)sqlite3_column_text(pStmt, 0)); + if( rc!=SQLITE_OK ){ + vacuumFinalize(db, pStmt, pzErrMsg); + return rc; + } + } + + return vacuumFinalize(db, pStmt, pzErrMsg); +} + +/* +** 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 */ + void (*saved_xTrace)(void*,const char*); /* Saved db->xTrace */ + 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 */ + + if( !db->autoCommit ){ + sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction"); + return SQLITE_ERROR; + } + if( db->activeVdbeCnt>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_xTrace = db->xTrace; + db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks | SQLITE_PreferBuiltin; + db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder); + db->xTrace = 0; + + 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. + */ + nDb = db->nDb; + if( sqlite3TempInMemory(db) ){ + zSql = "ATTACH ':memory:' AS vacuum_db;"; + }else{ + zSql = "ATTACH '' AS vacuum_db;"; + } + rc = execSql(db, pzErrMsg, zSql); + if( db->nDb>nDb ){ + pDb = &db->aDb[db->nDb-1]; + assert( strcmp(pDb->zName,"vacuum_db")==0 ); + } + if( rc!=SQLITE_OK ) goto end_of_vacuum; + 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 + + /* 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; + goto end_of_vacuum; + } + rc = execSql(db, pzErrMsg, "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, pzErrMsg, "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, pzErrMsg, + "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, pzErrMsg, + "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, pzErrMsg, + "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, pzErrMsg, + "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, pzErrMsg, + "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, pzErrMsg, + "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, pzErrMsg, + "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, 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 */ + }; + + 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; + db->xTrace = saved_xTrace; + 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. */ + sqlite3ResetInternalSchema(db, -1); + + return rc; +} + +#endif /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */ |