1 /* 2 ** 2003 April 6 3 ** 4 ** The author disclaims copyright to this source code. In place of 5 ** a legal notice, here is a blessing: 6 ** 7 ** May you do good and not evil. 8 ** May you find forgiveness for yourself and forgive others. 9 ** May you share freely, never taking more than you give. 10 ** 11 ************************************************************************* 12 ** This file contains code used to implement the VACUUM command. 13 ** 14 ** Most of the code in this file may be omitted by defining the 15 ** SQLITE_OMIT_VACUUM macro. 16 ** 17 ** $Id: vacuum.c,v 1.74 2007/10/20 20:58:57 drh Exp $ 18 */ 19 #include "sqliteInt.h" 20 #include "vdbeInt.h" 21 22 #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH) 23 /* 24 ** Execute zSql on database db. Return an error code. 25 */ 26 static int execSql(sqlite3 *db, const char *zSql){ 27 sqlite3_stmt *pStmt; 28 if( !zSql ){ 29 return SQLITE_NOMEM; 30 } 31 if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){ 32 return sqlite3_errcode(db); 33 } 34 while( SQLITE_ROW==sqlite3_step(pStmt) ){} 35 return sqlite3_finalize(pStmt); 36 } 37 38 /* 39 ** Execute zSql on database db. The statement returns exactly 40 ** one column. Execute this as SQL on the same database. 41 */ 42 static int execExecSql(sqlite3 *db, const char *zSql){ 43 sqlite3_stmt *pStmt; 44 int rc; 45 46 rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0); 47 if( rc!=SQLITE_OK ) return rc; 48 49 while( SQLITE_ROW==sqlite3_step(pStmt) ){ 50 rc = execSql(db, (char*)sqlite3_column_text(pStmt, 0)); 51 if( rc!=SQLITE_OK ){ 52 sqlite3_finalize(pStmt); 53 return rc; 54 } 55 } 56 57 return sqlite3_finalize(pStmt); 58 } 59 60 /* 61 ** The non-standard VACUUM command is used to clean up the database, 62 ** collapse free space, etc. It is modelled after the VACUUM command 63 ** in PostgreSQL. 64 ** 65 ** In version 1.0.x of SQLite, the VACUUM command would call 66 ** gdbm_reorganize() on all the database tables. But beginning 67 ** with 2.0.0, SQLite no longer uses GDBM so this command has 68 ** become a no-op. 69 */ 70 void sqlite3Vacuum(Parse *pParse){ 71 Vdbe *v = sqlite3GetVdbe(pParse); 72 if( v ){ 73 sqlite3VdbeAddOp(v, OP_Vacuum, 0, 0); 74 } 75 return; 76 } 77 78 /* 79 ** This routine implements the OP_Vacuum opcode of the VDBE. 80 */ 81 int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){ 82 int rc = SQLITE_OK; /* Return code from service routines */ 83 Btree *pMain; /* The database being vacuumed */ 84 Btree *pTemp; /* The temporary database we vacuum into */ 85 char *zSql = 0; /* SQL statements */ 86 int saved_flags; /* Saved value of the db->flags */ 87 Db *pDb = 0; /* Database to detach at end of vacuum */ 88 89 /* Save the current value of the write-schema flag before setting it. */ 90 saved_flags = db->flags; 91 db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks; 92 93 if( !db->autoCommit ){ 94 sqlite3SetString(pzErrMsg, "cannot VACUUM from within a transaction", 95 (char*)0); 96 rc = SQLITE_ERROR; 97 goto end_of_vacuum; 98 } 99 pMain = db->aDb[0].pBt; 100 101 /* Attach the temporary database as 'vacuum_db'. The synchronous pragma 102 ** can be set to 'off' for this file, as it is not recovered if a crash 103 ** occurs anyway. The integrity of the database is maintained by a 104 ** (possibly synchronous) transaction opened on the main database before 105 ** sqlite3BtreeCopyFile() is called. 106 ** 107 ** An optimisation would be to use a non-journaled pager. 108 */ 109 zSql = "ATTACH '' AS vacuum_db;"; 110 rc = execSql(db, zSql); 111 if( rc!=SQLITE_OK ) goto end_of_vacuum; 112 pDb = &db->aDb[db->nDb-1]; 113 assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 ); 114 pTemp = db->aDb[db->nDb-1].pBt; 115 sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), 116 sqlite3BtreeGetReserve(pMain)); 117 if( db->mallocFailed ){ 118 rc = SQLITE_NOMEM; 119 goto end_of_vacuum; 120 } 121 assert( sqlite3BtreeGetPageSize(pTemp)==sqlite3BtreeGetPageSize(pMain) ); 122 rc = execSql(db, "PRAGMA vacuum_db.synchronous=OFF"); 123 if( rc!=SQLITE_OK ){ 124 goto end_of_vacuum; 125 } 126 127 #ifndef SQLITE_OMIT_AUTOVACUUM 128 sqlite3BtreeSetAutoVacuum(pTemp, sqlite3BtreeGetAutoVacuum(pMain)); 129 #endif 130 131 /* Begin a transaction */ 132 rc = execSql(db, "BEGIN EXCLUSIVE;"); 133 if( rc!=SQLITE_OK ) goto end_of_vacuum; 134 135 /* Query the schema of the main database. Create a mirror schema 136 ** in the temporary database. 137 */ 138 rc = execExecSql(db, 139 "SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14) " 140 " FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'" 141 " AND rootpage>0" 142 ); 143 if( rc!=SQLITE_OK ) goto end_of_vacuum; 144 rc = execExecSql(db, 145 "SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14)" 146 " FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %' "); 147 if( rc!=SQLITE_OK ) goto end_of_vacuum; 148 rc = execExecSql(db, 149 "SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21) " 150 " FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'"); 151 if( rc!=SQLITE_OK ) goto end_of_vacuum; 152 153 /* Loop through the tables in the main database. For each, do 154 ** an "INSERT INTO vacuum_db.xxx SELECT * FROM xxx;" to copy 155 ** the contents to the temporary database. 156 */ 157 rc = execExecSql(db, 158 "SELECT 'INSERT INTO vacuum_db.' || quote(name) " 159 "|| ' SELECT * FROM ' || quote(name) || ';'" 160 "FROM sqlite_master " 161 "WHERE type = 'table' AND name!='sqlite_sequence' " 162 " AND rootpage>0" 163 164 ); 165 if( rc!=SQLITE_OK ) goto end_of_vacuum; 166 167 /* Copy over the sequence table 168 */ 169 rc = execExecSql(db, 170 "SELECT 'DELETE FROM vacuum_db.' || quote(name) || ';' " 171 "FROM vacuum_db.sqlite_master WHERE name='sqlite_sequence' " 172 ); 173 if( rc!=SQLITE_OK ) goto end_of_vacuum; 174 rc = execExecSql(db, 175 "SELECT 'INSERT INTO vacuum_db.' || quote(name) " 176 "|| ' SELECT * FROM ' || quote(name) || ';' " 177 "FROM vacuum_db.sqlite_master WHERE name=='sqlite_sequence';" 178 ); 179 if( rc!=SQLITE_OK ) goto end_of_vacuum; 180 181 182 /* Copy the triggers, views, and virtual tables from the main database 183 ** over to the temporary database. None of these objects has any 184 ** associated storage, so all we have to do is copy their entries 185 ** from the SQLITE_MASTER table. 186 */ 187 rc = execSql(db, 188 "INSERT INTO vacuum_db.sqlite_master " 189 " SELECT type, name, tbl_name, rootpage, sql" 190 " FROM sqlite_master" 191 " WHERE type='view' OR type='trigger'" 192 " OR (type='table' AND rootpage=0)" 193 ); 194 if( rc ) goto end_of_vacuum; 195 196 /* At this point, unless the main db was completely empty, there is now a 197 ** transaction open on the vacuum database, but not on the main database. 198 ** Open a btree level transaction on the main database. This allows a 199 ** call to sqlite3BtreeCopyFile(). The main database btree level 200 ** transaction is then committed, so the SQL level never knows it was 201 ** opened for writing. This way, the SQL transaction used to create the 202 ** temporary database never needs to be committed. 203 */ 204 if( rc==SQLITE_OK ){ 205 u32 meta; 206 int i; 207 208 /* This array determines which meta meta values are preserved in the 209 ** vacuum. Even entries are the meta value number and odd entries 210 ** are an increment to apply to the meta value after the vacuum. 211 ** The increment is used to increase the schema cookie so that other 212 ** connections to the same database will know to reread the schema. 213 */ 214 static const unsigned char aCopy[] = { 215 1, 1, /* Add one to the old schema cookie */ 216 3, 0, /* Preserve the default page cache size */ 217 5, 0, /* Preserve the default text encoding */ 218 6, 0, /* Preserve the user version */ 219 }; 220 221 assert( 1==sqlite3BtreeIsInTrans(pTemp) ); 222 assert( 1==sqlite3BtreeIsInTrans(pMain) ); 223 224 /* Copy Btree meta values */ 225 for(i=0; i<sizeof(aCopy)/sizeof(aCopy[0]); i+=2){ 226 rc = sqlite3BtreeGetMeta(pMain, aCopy[i], &meta); 227 if( rc!=SQLITE_OK ) goto end_of_vacuum; 228 rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]); 229 if( rc!=SQLITE_OK ) goto end_of_vacuum; 230 } 231 232 rc = sqlite3BtreeCopyFile(pMain, pTemp); 233 if( rc!=SQLITE_OK ) goto end_of_vacuum; 234 rc = sqlite3BtreeCommit(pTemp); 235 if( rc!=SQLITE_OK ) goto end_of_vacuum; 236 rc = sqlite3BtreeCommit(pMain); 237 } 238 239 end_of_vacuum: 240 /* Restore the original value of db->flags */ 241 db->flags = saved_flags; 242 243 /* Currently there is an SQL level transaction open on the vacuum 244 ** database. No locks are held on any other files (since the main file 245 ** was committed at the btree level). So it safe to end the transaction 246 ** by manually setting the autoCommit flag to true and detaching the 247 ** vacuum database. The vacuum_db journal file is deleted when the pager 248 ** is closed by the DETACH. 249 */ 250 db->autoCommit = 1; 251 252 if( pDb ){ 253 sqlite3BtreeClose(pDb->pBt); 254 pDb->pBt = 0; 255 pDb->pSchema = 0; 256 } 257 258 sqlite3ResetInternalSchema(db, 0); 259 260 return rc; 261 } 262 #endif /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */ 263