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1 /* |
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2 ** 2003 April 6 |
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3 ** |
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4 ** The author disclaims copyright to this source code. In place of |
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5 ** a legal notice, here is a blessing: |
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6 ** |
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7 ** May you do good and not evil. |
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8 ** May you find forgiveness for yourself and forgive others. |
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9 ** May you share freely, never taking more than you give. |
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10 ** |
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11 ************************************************************************* |
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12 ** This file contains code used to implement the VACUUM command. |
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13 ** |
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14 ** Most of the code in this file may be omitted by defining the |
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15 ** SQLITE_OMIT_VACUUM macro. |
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16 ** |
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17 ** $Id: vacuum.c,v 1.81 2008/07/08 19:34:07 drh Exp $ |
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18 */ |
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19 #include "sqliteInt.h" |
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20 #include "vdbeInt.h" |
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21 |
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22 #if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH) |
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23 /* |
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24 ** Execute zSql on database db. Return an error code. |
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25 */ |
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26 static int execSql(sqlite3 *db, const char *zSql){ |
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27 sqlite3_stmt *pStmt; |
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28 if( !zSql ){ |
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29 return SQLITE_NOMEM; |
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30 } |
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31 if( SQLITE_OK!=sqlite3_prepare(db, zSql, -1, &pStmt, 0) ){ |
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32 return sqlite3_errcode(db); |
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33 } |
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34 while( SQLITE_ROW==sqlite3_step(pStmt) ){} |
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35 return sqlite3_finalize(pStmt); |
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36 } |
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37 |
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38 /* |
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39 ** Execute zSql on database db. The statement returns exactly |
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40 ** one column. Execute this as SQL on the same database. |
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41 */ |
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42 static int execExecSql(sqlite3 *db, const char *zSql){ |
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43 sqlite3_stmt *pStmt; |
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44 int rc; |
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45 |
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46 rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0); |
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47 if( rc!=SQLITE_OK ) return rc; |
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48 |
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49 while( SQLITE_ROW==sqlite3_step(pStmt) ){ |
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50 rc = execSql(db, (char*)sqlite3_column_text(pStmt, 0)); |
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51 if( rc!=SQLITE_OK ){ |
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52 sqlite3_finalize(pStmt); |
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53 return rc; |
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54 } |
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55 } |
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56 |
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57 return sqlite3_finalize(pStmt); |
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58 } |
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59 |
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60 /* |
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61 ** The non-standard VACUUM command is used to clean up the database, |
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62 ** collapse free space, etc. It is modelled after the VACUUM command |
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63 ** in PostgreSQL. |
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64 ** |
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65 ** In version 1.0.x of SQLite, the VACUUM command would call |
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66 ** gdbm_reorganize() on all the database tables. But beginning |
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67 ** with 2.0.0, SQLite no longer uses GDBM so this command has |
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68 ** become a no-op. |
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69 */ |
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70 void sqlite3Vacuum(Parse *pParse){ |
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71 Vdbe *v = sqlite3GetVdbe(pParse); |
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72 if( v ){ |
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73 sqlite3VdbeAddOp2(v, OP_Vacuum, 0, 0); |
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74 } |
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75 return; |
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76 } |
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77 |
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78 /* |
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79 ** This routine implements the OP_Vacuum opcode of the VDBE. |
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80 */ |
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81 int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){ |
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82 int rc = SQLITE_OK; /* Return code from service routines */ |
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83 Btree *pMain; /* The database being vacuumed */ |
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84 Btree *pTemp; /* The temporary database we vacuum into */ |
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85 char *zSql = 0; /* SQL statements */ |
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86 int saved_flags; /* Saved value of the db->flags */ |
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87 int saved_nChange; /* Saved value of db->nChange */ |
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88 int saved_nTotalChange; /* Saved value of db->nTotalChange */ |
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89 Db *pDb = 0; /* Database to detach at end of vacuum */ |
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90 int nRes; |
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91 |
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92 /* Save the current value of the write-schema flag before setting it. */ |
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93 saved_flags = db->flags; |
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94 saved_nChange = db->nChange; |
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95 saved_nTotalChange = db->nTotalChange; |
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96 db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks; |
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97 |
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98 if( !db->autoCommit ){ |
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99 sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction"); |
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100 rc = SQLITE_ERROR; |
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101 goto end_of_vacuum; |
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102 } |
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103 pMain = db->aDb[0].pBt; |
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104 |
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105 /* Attach the temporary database as 'vacuum_db'. The synchronous pragma |
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106 ** can be set to 'off' for this file, as it is not recovered if a crash |
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107 ** occurs anyway. The integrity of the database is maintained by a |
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108 ** (possibly synchronous) transaction opened on the main database before |
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109 ** sqlite3BtreeCopyFile() is called. |
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110 ** |
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111 ** An optimisation would be to use a non-journaled pager. |
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112 ** (Later:) I tried setting "PRAGMA vacuum_db.journal_mode=OFF" but |
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113 ** that actually made the VACUUM run slower. Very little journalling |
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114 ** actually occurs when doing a vacuum since the vacuum_db is initially |
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115 ** empty. Only the journal header is written. Apparently it takes more |
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116 ** time to parse and run the PRAGMA to turn journalling off than it does |
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117 ** to write the journal header file. |
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118 */ |
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119 zSql = "ATTACH '' AS vacuum_db;"; |
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120 rc = execSql(db, zSql); |
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121 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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122 pDb = &db->aDb[db->nDb-1]; |
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123 assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 ); |
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124 pTemp = db->aDb[db->nDb-1].pBt; |
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125 |
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126 nRes = sqlite3BtreeGetReserve(pMain); |
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127 |
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128 /* A VACUUM cannot change the pagesize of an encrypted database. */ |
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129 #ifdef SQLITE_HAS_CODEC |
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130 if( db->nextPagesize ){ |
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131 extern void sqlite3CodecGetKey(sqlite3*, int, void**, int*); |
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132 int nKey; |
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133 char *zKey; |
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134 sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey); |
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135 if( nKey ) db->nextPagesize = 0; |
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136 } |
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137 #endif |
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138 |
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139 if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes) |
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140 || sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes) |
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141 || db->mallocFailed |
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142 ){ |
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143 rc = SQLITE_NOMEM; |
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144 goto end_of_vacuum; |
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145 } |
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146 rc = execSql(db, "PRAGMA vacuum_db.synchronous=OFF"); |
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147 if( rc!=SQLITE_OK ){ |
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148 goto end_of_vacuum; |
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149 } |
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150 |
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151 #ifndef SQLITE_OMIT_AUTOVACUUM |
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152 sqlite3BtreeSetAutoVacuum(pTemp, db->nextAutovac>=0 ? db->nextAutovac : |
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153 sqlite3BtreeGetAutoVacuum(pMain)); |
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154 #endif |
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155 |
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156 /* Begin a transaction */ |
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157 rc = execSql(db, "BEGIN EXCLUSIVE;"); |
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158 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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159 |
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160 /* Query the schema of the main database. Create a mirror schema |
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161 ** in the temporary database. |
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162 */ |
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163 rc = execExecSql(db, |
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164 "SELECT 'CREATE TABLE vacuum_db.' || substr(sql,14) " |
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165 " FROM sqlite_master WHERE type='table' AND name!='sqlite_sequence'" |
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166 " AND rootpage>0" |
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167 ); |
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168 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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169 rc = execExecSql(db, |
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170 "SELECT 'CREATE INDEX vacuum_db.' || substr(sql,14)" |
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171 " FROM sqlite_master WHERE sql LIKE 'CREATE INDEX %' "); |
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172 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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173 rc = execExecSql(db, |
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174 "SELECT 'CREATE UNIQUE INDEX vacuum_db.' || substr(sql,21) " |
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175 " FROM sqlite_master WHERE sql LIKE 'CREATE UNIQUE INDEX %'"); |
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176 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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177 |
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178 /* Loop through the tables in the main database. For each, do |
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179 ** an "INSERT INTO vacuum_db.xxx SELECT * FROM xxx;" to copy |
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180 ** the contents to the temporary database. |
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181 */ |
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182 rc = execExecSql(db, |
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183 "SELECT 'INSERT INTO vacuum_db.' || quote(name) " |
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184 "|| ' SELECT * FROM ' || quote(name) || ';'" |
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185 "FROM sqlite_master " |
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186 "WHERE type = 'table' AND name!='sqlite_sequence' " |
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187 " AND rootpage>0" |
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188 |
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189 ); |
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190 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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191 |
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192 /* Copy over the sequence table |
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193 */ |
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194 rc = execExecSql(db, |
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195 "SELECT 'DELETE FROM vacuum_db.' || quote(name) || ';' " |
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196 "FROM vacuum_db.sqlite_master WHERE name='sqlite_sequence' " |
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197 ); |
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198 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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199 rc = execExecSql(db, |
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200 "SELECT 'INSERT INTO vacuum_db.' || quote(name) " |
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201 "|| ' SELECT * FROM ' || quote(name) || ';' " |
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202 "FROM vacuum_db.sqlite_master WHERE name=='sqlite_sequence';" |
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203 ); |
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204 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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205 |
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206 |
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207 /* Copy the triggers, views, and virtual tables from the main database |
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208 ** over to the temporary database. None of these objects has any |
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209 ** associated storage, so all we have to do is copy their entries |
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210 ** from the SQLITE_MASTER table. |
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211 */ |
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212 rc = execSql(db, |
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213 "INSERT INTO vacuum_db.sqlite_master " |
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214 " SELECT type, name, tbl_name, rootpage, sql" |
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215 " FROM sqlite_master" |
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216 " WHERE type='view' OR type='trigger'" |
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217 " OR (type='table' AND rootpage=0)" |
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218 ); |
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219 if( rc ) goto end_of_vacuum; |
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220 |
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221 /* At this point, unless the main db was completely empty, there is now a |
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222 ** transaction open on the vacuum database, but not on the main database. |
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223 ** Open a btree level transaction on the main database. This allows a |
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224 ** call to sqlite3BtreeCopyFile(). The main database btree level |
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225 ** transaction is then committed, so the SQL level never knows it was |
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226 ** opened for writing. This way, the SQL transaction used to create the |
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227 ** temporary database never needs to be committed. |
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228 */ |
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229 if( rc==SQLITE_OK ){ |
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230 u32 meta; |
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231 int i; |
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232 |
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233 /* This array determines which meta meta values are preserved in the |
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234 ** vacuum. Even entries are the meta value number and odd entries |
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235 ** are an increment to apply to the meta value after the vacuum. |
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236 ** The increment is used to increase the schema cookie so that other |
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237 ** connections to the same database will know to reread the schema. |
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238 */ |
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239 static const unsigned char aCopy[] = { |
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240 1, 1, /* Add one to the old schema cookie */ |
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241 3, 0, /* Preserve the default page cache size */ |
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242 5, 0, /* Preserve the default text encoding */ |
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243 6, 0, /* Preserve the user version */ |
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244 }; |
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245 |
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246 assert( 1==sqlite3BtreeIsInTrans(pTemp) ); |
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247 assert( 1==sqlite3BtreeIsInTrans(pMain) ); |
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248 |
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249 /* Copy Btree meta values */ |
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250 for(i=0; i<sizeof(aCopy)/sizeof(aCopy[0]); i+=2){ |
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251 rc = sqlite3BtreeGetMeta(pMain, aCopy[i], &meta); |
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252 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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253 rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]); |
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254 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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255 } |
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256 |
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257 rc = sqlite3BtreeCopyFile(pMain, pTemp); |
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258 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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259 rc = sqlite3BtreeCommit(pTemp); |
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260 if( rc!=SQLITE_OK ) goto end_of_vacuum; |
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261 rc = sqlite3BtreeCommit(pMain); |
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262 } |
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263 |
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264 if( rc==SQLITE_OK ){ |
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265 rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes); |
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266 } |
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267 |
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268 end_of_vacuum: |
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269 /* Restore the original value of db->flags */ |
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270 db->flags = saved_flags; |
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271 db->nChange = saved_nChange; |
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272 db->nTotalChange = saved_nTotalChange; |
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273 |
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274 /* Currently there is an SQL level transaction open on the vacuum |
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275 ** database. No locks are held on any other files (since the main file |
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276 ** was committed at the btree level). So it safe to end the transaction |
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277 ** by manually setting the autoCommit flag to true and detaching the |
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278 ** vacuum database. The vacuum_db journal file is deleted when the pager |
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279 ** is closed by the DETACH. |
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280 */ |
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281 db->autoCommit = 1; |
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282 |
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283 if( pDb ){ |
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284 sqlite3BtreeClose(pDb->pBt); |
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285 pDb->pBt = 0; |
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286 pDb->pSchema = 0; |
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287 } |
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288 |
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289 sqlite3ResetInternalSchema(db, 0); |
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290 |
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291 return rc; |
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292 } |
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293 #endif /* SQLITE_OMIT_VACUUM && SQLITE_OMIT_ATTACH */ |