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 #include "sqliteInt.h" 18 #include "vdbeInt.h" 19 20 #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH) 21 /* 22 ** Finalize a prepared statement. If there was an error, store the 23 ** text of the error message in *pzErrMsg. Return the result code. 24 */ 25 static int vacuumFinalize(sqlite3 *db, sqlite3_stmt *pStmt, char **pzErrMsg){ 26 int rc; 27 rc = sqlite3VdbeFinalize((Vdbe*)pStmt); 28 if( rc ){ 29 sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db)); 30 } 31 return rc; 32 } 33 34 /* 35 ** Execute zSql on database db. Return an error code. 36 */ 37 static int execSql(sqlite3 *db, char **pzErrMsg, const char *zSql){ 38 sqlite3_stmt *pStmt; 39 VVA_ONLY( int rc; ) 40 if( !zSql ){ 41 return SQLITE_NOMEM; 42 } 43 if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){ 44 sqlite3SetString(pzErrMsg, db, sqlite3_errmsg(db)); 45 return sqlite3_errcode(db); 46 } 47 VVA_ONLY( rc = ) sqlite3_step(pStmt); 48 assert( rc!=SQLITE_ROW ); 49 return vacuumFinalize(db, pStmt, pzErrMsg); 50 } 51 52 /* 53 ** Execute zSql on database db. The statement returns exactly 54 ** one column. Execute this as SQL on the same database. 55 */ 56 static int execExecSql(sqlite3 *db, char **pzErrMsg, const char *zSql){ 57 sqlite3_stmt *pStmt; 58 int rc; 59 60 rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0); 61 if( rc!=SQLITE_OK ) return rc; 62 63 while( SQLITE_ROW==sqlite3_step(pStmt) ){ 64 rc = execSql(db, pzErrMsg, (char*)sqlite3_column_text(pStmt, 0)); 65 if( rc!=SQLITE_OK ){ 66 vacuumFinalize(db, pStmt, pzErrMsg); 67 return rc; 68 } 69 } 70 71 return vacuumFinalize(db, pStmt, pzErrMsg); 72 } 73 74 /* 75 ** The non-standard VACUUM command is used to clean up the database, 76 ** collapse free space, etc. It is modelled after the VACUUM command 77 ** in PostgreSQL. 78 ** 79 ** In version 1.0.x of SQLite, the VACUUM command would call 80 ** gdbm_reorganize() on all the database tables. But beginning 81 ** with 2.0.0, SQLite no longer uses GDBM so this command has 82 ** become a no-op. 83 */ 84 void sqlite3Vacuum(Parse *pParse){ 85 Vdbe *v = sqlite3GetVdbe(pParse); 86 if( v ){ 87 sqlite3VdbeAddOp2(v, OP_Vacuum, 0, 0); 88 } 89 return; 90 } 91 92 /* 93 ** This routine implements the OP_Vacuum opcode of the VDBE. 94 */ 95 int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){ 96 int rc = SQLITE_OK; /* Return code from service routines */ 97 Btree *pMain; /* The database being vacuumed */ 98 Btree *pTemp; /* The temporary database we vacuum into */ 99 char *zSql = 0; /* SQL statements */ 100 int saved_flags; /* Saved value of the db->flags */ 101 int saved_nChange; /* Saved value of db->nChange */ 102 int saved_nTotalChange; /* Saved value of db->nTotalChange */ 103 void (*saved_xTrace)(void*,const char*); /* Saved db->xTrace */ 104 Db *pDb = 0; /* Database to detach at end of vacuum */ 105 int isMemDb; /* True if vacuuming a :memory: database */ 106 int nRes; /* Bytes of reserved space at the end of each page */ 107 int nDb; /* Number of attached databases */ 108 109 if( !db->autoCommit ){ 110 sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction"); 111 return SQLITE_ERROR; 112 } 113 if( db->activeVdbeCnt>1 ){ 114 sqlite3SetString(pzErrMsg, db,"cannot VACUUM - SQL statements in progress"); 115 return SQLITE_ERROR; 116 } 117 118 /* Save the current value of the database flags so that it can be 119 ** restored before returning. Then set the writable-schema flag, and 120 ** disable CHECK and foreign key constraints. */ 121 saved_flags = db->flags; 122 saved_nChange = db->nChange; 123 saved_nTotalChange = db->nTotalChange; 124 saved_xTrace = db->xTrace; 125 db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks | SQLITE_PreferBuiltin; 126 db->flags &= ~(SQLITE_ForeignKeys | SQLITE_ReverseOrder); 127 db->xTrace = 0; 128 129 pMain = db->aDb[0].pBt; 130 isMemDb = sqlite3PagerIsMemdb(sqlite3BtreePager(pMain)); 131 132 /* Attach the temporary database as 'vacuum_db'. The synchronous pragma 133 ** can be set to 'off' for this file, as it is not recovered if a crash 134 ** occurs anyway. The integrity of the database is maintained by a 135 ** (possibly synchronous) transaction opened on the main database before 136 ** sqlite3BtreeCopyFile() is called. 137 ** 138 ** An optimisation would be to use a non-journaled pager. 139 ** (Later:) I tried setting "PRAGMA vacuum_db.journal_mode=OFF" but 140 ** that actually made the VACUUM run slower. Very little journalling 141 ** actually occurs when doing a vacuum since the vacuum_db is initially 142 ** empty. Only the journal header is written. Apparently it takes more 143 ** time to parse and run the PRAGMA to turn journalling off than it does 144 ** to write the journal header file. 145 */ 146 nDb = db->nDb; 147 if( sqlite3TempInMemory(db) ){ 148 zSql = "ATTACH ':memory:' AS vacuum_db;"; 149 }else{ 150 zSql = "ATTACH '' AS vacuum_db;"; 151 } 152 rc = execSql(db, pzErrMsg, zSql); 153 if( db->nDb>nDb ){ 154 pDb = &db->aDb[db->nDb-1]; 155 assert( strcmp(pDb->zName,"vacuum_db")==0 ); 156 } 157 if( rc!=SQLITE_OK ) goto end_of_vacuum; 158 pTemp = db->aDb[db->nDb-1].pBt; 159 160 /* The call to execSql() to attach the temp database has left the file 161 ** locked (as there was more than one active statement when the transaction 162 ** to read the schema was concluded. Unlock it here so that this doesn't 163 ** cause problems for the call to BtreeSetPageSize() below. */ 164 sqlite3BtreeCommit(pTemp); 165 166 nRes = sqlite3BtreeGetReserve(pMain); 167 168 /* A VACUUM cannot change the pagesize of an encrypted database. */ 169 #ifdef SQLITE_HAS_CODEC 170 if( db->nextPagesize ){ 171 extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*); 172 int nKey; 173 char *zKey; 174 sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey); 175 if( nKey ) db->nextPagesize = 0; 176 } 177 #endif 178 179 /* Do not attempt to change the page size for a WAL database */ 180 if( sqlite3PagerGetJournalMode(sqlite3BtreePager(pMain)) 181 ==PAGER_JOURNALMODE_WAL ){ 182 db->nextPagesize = 0; 183 } 184 185 if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0) 186 || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0)) 187 || NEVER(db->mallocFailed) 188 ){ 189 rc = SQLITE_NOMEM; 190 goto end_of_vacuum; 191 } 192 rc = execSql(db, pzErrMsg, "PRAGMA vacuum_db.synchronous=OFF"); 193 if( rc!=SQLITE_OK ){ 194 goto end_of_vacuum; 195 } 196 197 #ifndef SQLITE_OMIT_AUTOVACUUM 198 sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac : 199 sqlite3BtreeGetAutoVacuum(pMain)); 200 #endif 201 202 /* Begin a transaction */ 203 rc = execSql(db, pzErrMsg, "BEGIN EXCLUSIVE;"); 204 if( rc!=SQLITE_OK ) goto end_of_vacuum; 205 206 /* Query the schema of the main database. Create a mirror schema 207 ** in the temporary database. 208 */ 209 rc = execExecSql(db, pzErrMsg, 210 "SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14) " 211 " FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'" 212 " AND rootpage>0" 213 ); 214 if( rc!=SQLITE_OK ) goto end_of_vacuum; 215 rc = execExecSql(db, pzErrMsg, 216 "SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14)" 217 " FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %' "); 218 if( rc!=SQLITE_OK ) goto end_of_vacuum; 219 rc = execExecSql(db, pzErrMsg, 220 "SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21) " 221 " FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'"); 222 if( rc!=SQLITE_OK ) goto end_of_vacuum; 223 224 /* Loop through the tables in the main database. For each, do 225 ** an "INSERT INTO vacuum_db.xxx SELECT * FROM main.xxx;" to copy 226 ** the contents to the temporary database. 227 */ 228 rc = execExecSql(db, pzErrMsg, 229 "SELECT 'INSERT INTO vacuum_db.' || quote(name) " 230 "|| ' SELECT * FROM main.' || quote(name) || ';'" 231 "FROM main.sqlite_master " 232 "WHERE type = 'table' AND name!='sqlite_sequence' " 233 " AND rootpage>0" 234 ); 235 if( rc!=SQLITE_OK ) goto end_of_vacuum; 236 237 /* Copy over the sequence table 238 */ 239 rc = execExecSql(db, pzErrMsg, 240 "SELECT 'DELETE FROM vacuum_db.' || quote(name) || ';' " 241 "FROM vacuum_db.sqlite_master WHERE name='sqlite_sequence' " 242 ); 243 if( rc!=SQLITE_OK ) goto end_of_vacuum; 244 rc = execExecSql(db, pzErrMsg, 245 "SELECT 'INSERT INTO vacuum_db.' || quote(name) " 246 "|| ' SELECT * FROM main.' || quote(name) || ';' " 247 "FROM vacuum_db.sqlite_master WHERE name=='sqlite_sequence';" 248 ); 249 if( rc!=SQLITE_OK ) goto end_of_vacuum; 250 251 252 /* Copy the triggers, views, and virtual tables from the main database 253 ** over to the temporary database. None of these objects has any 254 ** associated storage, so all we have to do is copy their entries 255 ** from the SQLITE_MASTER table. 256 */ 257 rc = execSql(db, pzErrMsg, 258 "INSERT INTO vacuum_db.sqlite_master " 259 " SELECT type, name, tbl_name, rootpage, sql" 260 " FROM main.sqlite_master" 261 " WHERE type='view' OR type='trigger'" 262 " OR (type='table' AND rootpage=0)" 263 ); 264 if( rc ) goto end_of_vacuum; 265 266 /* At this point, unless the main db was completely empty, there is now a 267 ** transaction open on the vacuum database, but not on the main database. 268 ** Open a btree level transaction on the main database. This allows a 269 ** call to sqlite3BtreeCopyFile(). The main database btree level 270 ** transaction is then committed, so the SQL level never knows it was 271 ** opened for writing. This way, the SQL transaction used to create the 272 ** temporary database never needs to be committed. 273 */ 274 { 275 u32 meta; 276 int i; 277 278 /* This array determines which meta meta values are preserved in the 279 ** vacuum. Even entries are the meta value number and odd entries 280 ** are an increment to apply to the meta value after the vacuum. 281 ** The increment is used to increase the schema cookie so that other 282 ** connections to the same database will know to reread the schema. 283 */ 284 static const unsigned char aCopy[] = { 285 BTREE_SCHEMA_VERSION, 1, /* Add one to the old schema cookie */ 286 BTREE_DEFAULT_CACHE_SIZE, 0, /* Preserve the default page cache size */ 287 BTREE_TEXT_ENCODING, 0, /* Preserve the text encoding */ 288 BTREE_USER_VERSION, 0, /* Preserve the user version */ 289 }; 290 291 assert( 1==sqlite3BtreeIsInTrans(pTemp) ); 292 assert( 1==sqlite3BtreeIsInTrans(pMain) ); 293 294 /* Copy Btree meta values */ 295 for(i=0; i<ArraySize(aCopy); i+=2){ 296 /* GetMeta() and UpdateMeta() cannot fail in this context because 297 ** we already have page 1 loaded into cache and marked dirty. */ 298 sqlite3BtreeGetMeta(pMain, aCopy[i], &meta); 299 rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]); 300 if( NEVER(rc!=SQLITE_OK) ) goto end_of_vacuum; 301 } 302 303 rc = sqlite3BtreeCopyFile(pMain, pTemp); 304 if( rc!=SQLITE_OK ) goto end_of_vacuum; 305 rc = sqlite3BtreeCommit(pTemp); 306 if( rc!=SQLITE_OK ) goto end_of_vacuum; 307 #ifndef SQLITE_OMIT_AUTOVACUUM 308 sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp)); 309 #endif 310 } 311 312 assert( rc==SQLITE_OK ); 313 rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1); 314 315 end_of_vacuum: 316 /* Restore the original value of db->flags */ 317 db->flags = saved_flags; 318 db->nChange = saved_nChange; 319 db->nTotalChange = saved_nTotalChange; 320 db->xTrace = saved_xTrace; 321 sqlite3BtreeSetPageSize(pMain, -1, -1, 1); 322 323 /* Currently there is an SQL level transaction open on the vacuum 324 ** database. No locks are held on any other files (since the main file 325 ** was committed at the btree level). So it safe to end the transaction 326 ** by manually setting the autoCommit flag to true and detaching the 327 ** vacuum database. The vacuum_db journal file is deleted when the pager 328 ** is closed by the DETACH. 329 */ 330 db->autoCommit = 1; 331 332 if( pDb ){ 333 sqlite3BtreeClose(pDb->pBt); 334 pDb->pBt = 0; 335 pDb->pSchema = 0; 336 } 337 338 /* This both clears the schemas and reduces the size of the db->aDb[] 339 ** array. */ 340 sqlite3ResetInternalSchema(db, -1); 341 342 return rc; 343 } 344 345 #endif /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */ 346
