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Diffstat (limited to 'src/sqlite/vacuum.c')
| -rw-r--r-- | src/sqlite/vacuum.c | 310 |
1 files changed, 310 insertions, 0 deletions
diff --git a/src/sqlite/vacuum.c b/src/sqlite/vacuum.c new file mode 100644 index 0000000..b85d36d --- /dev/null +++ b/src/sqlite/vacuum.c @@ -0,0 +1,310 @@ +/* +** 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 1.1.1.1 2006/02/03 20:35:17 hoganrobert Exp $ +*/ +#include "sqliteInt.h" +#include "os.h" + +#ifndef SQLITE_OMIT_VACUUM +/* +** Generate a random name of 20 character in length. +*/ +static void randomName(unsigned char *zBuf){ + static const unsigned char zChars[] = + "abcdefghijklmnopqrstuvwxyz" + "0123456789"; + int i; + sqlite3Randomness(20, zBuf); + for(i=0; i<20; i++){ + zBuf[i] = zChars[ zBuf[i]%(sizeof(zChars)-1) ]; + } +} + +/* +** Execute zSql on database db. Return an error code. +*/ +static int execSql(sqlite3 *db, const char *zSql){ + sqlite3_stmt *pStmt; + 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, sqlite3_column_text(pStmt, 0)); + if( rc!=SQLITE_OK ){ + sqlite3_finalize(pStmt); + return rc; + } + } + + return sqlite3_finalize(pStmt); +} + +#endif + +/* +** 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, Token *pTableName){ + Vdbe *v = sqlite3GetVdbe(pParse); + if( v ){ + sqlite3VdbeAddOp(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 */ +#ifndef SQLITE_OMIT_VACUUM + const char *zFilename; /* full pathname of the database file */ + int nFilename; /* number of characters in zFilename[] */ + char *zTemp = 0; /* a temporary file in same directory as zFilename */ + Btree *pMain; /* The database being vacuumed */ + Btree *pTemp; + char *zSql = 0; + int writeschema_flag; /* Saved value of the write-schema flag */ + + /* Save the current value of the write-schema flag before setting it. */ + writeschema_flag = db->flags&SQLITE_WriteSchema; + db->flags |= SQLITE_WriteSchema; + + if( !db->autoCommit ){ + sqlite3SetString(pzErrMsg, "cannot VACUUM from within a transaction", + (char*)0); + rc = SQLITE_ERROR; + goto end_of_vacuum; + } + + /* Get the full pathname of the database file and create a + ** temporary filename in the same directory as the original file. + */ + pMain = db->aDb[0].pBt; + zFilename = sqlite3BtreeGetFilename(pMain); + assert( zFilename ); + if( zFilename[0]=='\0' ){ + /* The in-memory database. Do nothing. Return directly to avoid causing + ** an error trying to DETACH the vacuum_db (which never got attached) + ** in the exit-handler. + */ + return SQLITE_OK; + } + nFilename = strlen(zFilename); + zTemp = sqliteMalloc( nFilename+100 ); + if( zTemp==0 ){ + rc = SQLITE_NOMEM; + goto end_of_vacuum; + } + strcpy(zTemp, zFilename); + + /* The randomName() procedure in the following loop uses an excellent + ** source of randomness to generate a name from a space of 1.3e+31 + ** possibilities. So unless the directory already contains on the order + ** of 1.3e+31 files, the probability that the following loop will + ** run more than once or twice is vanishingly small. We are certain + ** enough that this loop will always terminate (and terminate quickly) + ** that we don't even bother to set a maximum loop count. + */ + do { + zTemp[nFilename] = '-'; + randomName((unsigned char*)&zTemp[nFilename+1]); + } while( sqlite3OsFileExists(zTemp) ); + + /* 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 = sqlite3MPrintf("ATTACH '%q' AS vacuum_db;", zTemp); + if( !zSql ){ + rc = SQLITE_NOMEM; + goto end_of_vacuum; + } + rc = execSql(db, zSql); + sqliteFree(zSql); + zSql = 0; + if( rc!=SQLITE_OK ) goto end_of_vacuum; + assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 ); + pTemp = db->aDb[db->nDb-1].pBt; + sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), + sqlite3BtreeGetReserve(pMain)); + assert( sqlite3BtreeGetPageSize(pTemp)==sqlite3BtreeGetPageSize(pMain) ); + execSql(db, "PRAGMA vacuum_db.synchronous=OFF"); + +#ifndef SQLITE_OMIT_AUTOVACUUM + sqlite3BtreeSetAutoVacuum(pTemp, sqlite3BtreeGetAutoVacuum(pMain)); +#endif + + /* Begin a transaction */ + rc = execSql(db, "BEGIN;"); + 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,14,100000000) " + " FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'"); + if( rc!=SQLITE_OK ) goto end_of_vacuum; + rc = execExecSql(db, + "SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14,100000000)" + " 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,21,100000000) " + " FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'"); + if( rc!=SQLITE_OK ) goto end_of_vacuum; + rc = execExecSql(db, + "SELECT 'CREATE VIEW vacuum_db.' || substr(sql,13,100000000) " + " FROM sqlite_master WHERE type='view'" + ); + 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';" + ); + 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 from the main database to the temporary database. + ** This was deferred before in case the triggers interfered with copying + ** the data. It's possible the indices should be deferred until this + ** point also. + */ + rc = execExecSql(db, + "SELECT 'CREATE TRIGGER vacuum_db.' || substr(sql, 16, 1000000) " + "FROM sqlite_master WHERE type='trigger'" + ); + if( rc!=SQLITE_OK ) 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( sqlite3BtreeIsInTrans(pTemp) ){ + 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( 0==sqlite3BtreeIsInTrans(pMain) ); + rc = sqlite3BtreeBeginTrans(pMain, 1); + if( rc!=SQLITE_OK ) goto end_of_vacuum; + + /* 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]); + } + + rc = sqlite3BtreeCopyFile(pMain, pTemp); + if( rc!=SQLITE_OK ) goto end_of_vacuum; + rc = sqlite3BtreeCommit(pMain); + } + +end_of_vacuum: + /* Restore the original value of the write-schema flag. */ + db->flags &= ~SQLITE_WriteSchema; + db->flags |= writeschema_flag; + + /* 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( rc==SQLITE_OK ){ + rc = execSql(db, "DETACH vacuum_db;"); + }else{ + execSql(db, "DETACH vacuum_db;"); + } + if( zTemp ){ + sqlite3OsDelete(zTemp); + sqliteFree(zTemp); + } + if( zSql ) sqliteFree( zSql ); + sqlite3ResetInternalSchema(db, 0); +#endif + + return rc; +} |