src/prepare.c

   1 /*
   2 ** 2005 May 25
   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 the implementation of the sqlite3_prepare()
  13 ** interface, and routines that contribute to loading the database schema
  14 ** from disk.
  15 */
  16 #include "sqliteInt.h"
  17
  18 /*
  19 ** Fill the InitData structure with an error message that indicates
  20 ** that the database is corrupt.
  21 */
  22 static void corruptSchema(
  23   InitData *pData,     /* Initialization context */
  24   const char *zObj,    /* Object being parsed at the point of error */
  25   const char *zExtra   /* Error information */
  26 ){
  27   sqlite3 *db = pData->db;
  28   if( !db->mallocFailed && (db->flags & SQLITE_WriteSchema)==0 ){
  29     char *z;
  30     if( zObj==0 ) zObj = "?";
  31     z = sqlite3MPrintf(db, "malformed database schema (%s)", zObj);
  32     if( zExtra ) z = sqlite3MPrintf(db, "%z - %s", z, zExtra);
  33     sqlite3DbFree(db, *pData->pzErrMsg);
  34     *pData->pzErrMsg = z;
  35   }
  36   pData->rc = db->mallocFailed ? SQLITE_NOMEM_BKPT : SQLITE_CORRUPT_BKPT;
  37 }
  38
  39 /*
  40 ** This is the callback routine for the code that initializes the
  41 ** database.  See sqlite3Init() below for additional information.
  42 ** This routine is also called from the OP_ParseSchema opcode of the VDBE.
  43 **
  44 ** Each callback contains the following information:
  45 **
  46 **     argv[0] = name of thing being created
  47 **     argv[1] = root page number for table or index. 0 for trigger or view.
  48 **     argv[2] = SQL text for the CREATE statement.
  49 **
  50 */
  51 int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
  52   InitData *pData = (InitData*)pInit;
  53   sqlite3 *db = pData->db;
  54   int iDb = pData->iDb;
  55
  56   assert( argc==3 );
  57   UNUSED_PARAMETER2(NotUsed, argc);
  58   assert( sqlite3_mutex_held(db->mutex) );
  59   DbClearProperty(db, iDb, DB_Empty);
  60   if( db->mallocFailed ){
  61     corruptSchema(pData, argv[0], 0);
  62     return 1;
  63   }
  64
  65   assert( iDb>=0 && iDb<db->nDb );
  66   if( argv==0 ) return 0;   /* Might happen if EMPTY_RESULT_CALLBACKS are on */
  67   if( argv[1]==0 ){
  68     corruptSchema(pData, argv[0], 0);
  69   }else if( sqlite3_strnicmp(argv[2],"create ",7)==0 ){
  70     /* Call the parser to process a CREATE TABLE, INDEX or VIEW.
  71     ** But because db->init.busy is set to 1, no VDBE code is generated
  72     ** or executed.  All the parser does is build the internal data
  73     ** structures that describe the table, index, or view.
  74     */
  75     int rc;
  76     u8 saved_iDb = db->init.iDb;
  77     sqlite3_stmt *pStmt;
  78     TESTONLY(int rcp);            /* Return code from sqlite3_prepare() */
  79
  80     assert( db->init.busy );
  81     db->init.iDb = iDb;
  82     db->init.newTnum = sqlite3Atoi(argv[1]);
  83     db->init.orphanTrigger = 0;
  84     TESTONLY(rcp = ) sqlite3_prepare(db, argv[2], -1, &pStmt, 0);
  85     rc = db->errCode;
  86     assert( (rc&0xFF)==(rcp&0xFF) );
  87     db->init.iDb = saved_iDb;
  88     assert( saved_iDb==0 || (db->flags & SQLITE_Vacuum)!=0 );
  89     if( SQLITE_OK!=rc ){
  90       if( db->init.orphanTrigger ){
  91         assert( iDb==1 );
  92       }else{
  93         pData->rc = rc;
  94         if( rc==SQLITE_NOMEM ){
  95           sqlite3OomFault(db);
  96         }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED ){
  97           corruptSchema(pData, argv[0], sqlite3_errmsg(db));
  98         }
  99       }
 100     }
 101     sqlite3_finalize(pStmt);
 102   }else if( argv[0]==0 || (argv[2]!=0 && argv[2][0]!=0) ){
 103     corruptSchema(pData, argv[0], 0);
 104   }else{
 105     /* If the SQL column is blank it means this is an index that
 106     ** was created to be the PRIMARY KEY or to fulfill a UNIQUE
 107     ** constraint for a CREATE TABLE.  The index should have already
 108     ** been created when we processed the CREATE TABLE.  All we have
 109     ** to do here is record the root page number for that index.
 110     */
 111     Index *pIndex;
 112     pIndex = sqlite3FindIndex(db, argv[0], db->aDb[iDb].zDbSName);
 113     if( pIndex==0 ){
 114       /* This can occur if there exists an index on a TEMP table which
 115       ** has the same name as another index on a permanent index.  Since
 116       ** the permanent table is hidden by the TEMP table, we can also
 117       ** safely ignore the index on the permanent table.
 118       */
 119       /* Do Nothing */;
 120     }else if( sqlite3GetInt32(argv[1], &pIndex->tnum)==0 ){
 121       corruptSchema(pData, argv[0], "invalid rootpage");
 122     }
 123   }
 124   return 0;
 125 }
 126
 127 /*
 128 ** Attempt to read the database schema and initialize internal
 129 ** data structures for a single database file.  The index of the
 130 ** database file is given by iDb.  iDb==0 is used for the main
 131 ** database.  iDb==1 should never be used.  iDb>=2 is used for
 132 ** auxiliary databases.  Return one of the SQLITE_ error codes to
 133 ** indicate success or failure.
 134 */
 135 static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
 136   int rc;
 137   int i;
 138 #ifndef SQLITE_OMIT_DEPRECATED
 139   int size;
 140 #endif
 141   Db *pDb;
 142   char const *azArg[4];
 143   int meta[5];
 144   InitData initData;
 145   const char *zMasterName;
 146   int openedTransaction = 0;
 147
 148   assert( iDb>=0 && iDb<db->nDb );
 149   assert( db->aDb[iDb].pSchema );
 150   assert( sqlite3_mutex_held(db->mutex) );
 151   assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
 152
 153   /* Construct the in-memory representation schema tables (sqlite_master or
 154   ** sqlite_temp_master) by invoking the parser directly.  The appropriate
 155   ** table name will be inserted automatically by the parser so we can just
 156   ** use the abbreviation "x" here.  The parser will also automatically tag
 157   ** the schema table as read-only. */
 158   azArg[0] = zMasterName = SCHEMA_TABLE(iDb);
 159   azArg[1] = "1";
 160   azArg[2] = "CREATE TABLE x(type text,name text,tbl_name text,"
 161                             "rootpage integer,sql text)";
 162   azArg[3] = 0;
 163   initData.db = db;
 164   initData.iDb = iDb;
 165   initData.rc = SQLITE_OK;
 166   initData.pzErrMsg = pzErrMsg;
 167   sqlite3InitCallback(&initData, 3, (char **)azArg, 0);
 168   if( initData.rc ){
 169     rc = initData.rc;
 170     goto error_out;
 171   }
 172
 173   /* Create a cursor to hold the database open
 174   */
 175   pDb = &db->aDb[iDb];
 176   if( pDb->pBt==0 ){
 177     if( !OMIT_TEMPDB && ALWAYS(iDb==1) ){
 178       DbSetProperty(db, 1, DB_SchemaLoaded);
 179     }
 180     return SQLITE_OK;
 181   }
 182
 183   /* If there is not already a read-only (or read-write) transaction opened
 184   ** on the b-tree database, open one now. If a transaction is opened, it
 185   ** will be closed before this function returns.  */
 186   sqlite3BtreeEnter(pDb->pBt);
 187   if( !sqlite3BtreeIsInReadTrans(pDb->pBt) ){
 188     rc = sqlite3BtreeBeginTrans(pDb->pBt, 0);
 189     if( rc!=SQLITE_OK ){
 190       sqlite3SetString(pzErrMsg, db, sqlite3ErrStr(rc));
 191       goto initone_error_out;
 192     }
 193     openedTransaction = 1;
 194   }
 195
 196   /* Get the database meta information.
 197   **
 198   ** Meta values are as follows:
 199   **    meta[0]   Schema cookie.  Changes with each schema change.
 200   **    meta[1]   File format of schema layer.
 201   **    meta[2]   Size of the page cache.
 202   **    meta[3]   Largest rootpage (auto/incr_vacuum mode)
 203   **    meta[4]   Db text encoding. 1:UTF-8 2:UTF-16LE 3:UTF-16BE
 204   **    meta[5]   User version
 205   **    meta[6]   Incremental vacuum mode
 206   **    meta[7]   unused
 207   **    meta[8]   unused
 208   **    meta[9]   unused
 209   **
 210   ** Note: The #defined SQLITE_UTF* symbols in sqliteInt.h correspond to
 211   ** the possible values of meta[4].
 212   */
 213   for(i=0; i<ArraySize(meta); i++){
 214     sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
 215   }
 216   pDb->pSchema->schema_cookie = meta[BTREE_SCHEMA_VERSION-1];
 217
 218   /* If opening a non-empty database, check the text encoding. For the
 219   ** main database, set sqlite3.enc to the encoding of the main database.
 220   ** For an attached db, it is an error if the encoding is not the same
 221   ** as sqlite3.enc.
 222   */
 223   if( meta[BTREE_TEXT_ENCODING-1] ){  /* text encoding */
 224     if( iDb==0 ){
 225 #ifndef SQLITE_OMIT_UTF16
 226       u8 encoding;
 227       /* If opening the main database, set ENC(db). */
 228       encoding = (u8)meta[BTREE_TEXT_ENCODING-1] & 3;
 229       if( encoding==0 ) encoding = SQLITE_UTF8;
 230       ENC(db) = encoding;
 231 #else
 232       ENC(db) = SQLITE_UTF8;
 233 #endif
 234     }else{
 235       /* If opening an attached database, the encoding much match ENC(db) */
 236       if( meta[BTREE_TEXT_ENCODING-1]!=ENC(db) ){
 237         sqlite3SetString(pzErrMsg, db, "attached databases must use the same"
 238             " text encoding as main database");
 239         rc = SQLITE_ERROR;
 240         goto initone_error_out;
 241       }
 242     }
 243   }else{
 244     DbSetProperty(db, iDb, DB_Empty);
 245   }
 246   pDb->pSchema->enc = ENC(db);
 247
 248   if( pDb->pSchema->cache_size==0 ){
 249 #ifndef SQLITE_OMIT_DEPRECATED
 250     size = sqlite3AbsInt32(meta[BTREE_DEFAULT_CACHE_SIZE-1]);
 251     if( size==0 ){ size = SQLITE_DEFAULT_CACHE_SIZE; }
 252     pDb->pSchema->cache_size = size;
 253 #else
 254     pDb->pSchema->cache_size = SQLITE_DEFAULT_CACHE_SIZE;
 255 #endif
 256     sqlite3BtreeSetCacheSize(pDb->pBt, pDb->pSchema->cache_size);
 257   }
 258
 259   /*
 260   ** file_format==1    Version 3.0.0.
 261   ** file_format==2    Version 3.1.3.  // ALTER TABLE ADD COLUMN
 262   ** file_format==3    Version 3.1.4.  // ditto but with non-NULL defaults
 263   ** file_format==4    Version 3.3.0.  // DESC indices.  Boolean constants
 264   */
 265   pDb->pSchema->file_format = (u8)meta[BTREE_FILE_FORMAT-1];
 266   if( pDb->pSchema->file_format==0 ){
 267     pDb->pSchema->file_format = 1;
 268   }
 269   if( pDb->pSchema->file_format>SQLITE_MAX_FILE_FORMAT ){
 270     sqlite3SetString(pzErrMsg, db, "unsupported file format");
 271     rc = SQLITE_ERROR;
 272     goto initone_error_out;
 273   }
 274
 275   /* Ticket #2804:  When we open a database in the newer file format,
 276   ** clear the legacy_file_format pragma flag so that a VACUUM will
 277   ** not downgrade the database and thus invalidate any descending
 278   ** indices that the user might have created.
 279   */
 280   if( iDb==0 && meta[BTREE_FILE_FORMAT-1]>=4 ){
 281     db->flags &= ~SQLITE_LegacyFileFmt;
 282   }
 283
 284   /* Read the schema information out of the schema tables
 285   */
 286   assert( db->init.busy );
 287   {
 288     char *zSql;
 289     zSql = sqlite3MPrintf(db,
 290         "SELECT name, rootpage, sql FROM \"%w\".%s ORDER BY rowid",
 291         db->aDb[iDb].zDbSName, zMasterName);
 292 #ifndef SQLITE_OMIT_AUTHORIZATION
 293     {
 294       sqlite3_xauth xAuth;
 295       xAuth = db->xAuth;
 296       db->xAuth = 0;
 297 #endif
 298       rc = sqlite3_exec(db, zSql, sqlite3InitCallback, &initData, 0);
 299 #ifndef SQLITE_OMIT_AUTHORIZATION
 300       db->xAuth = xAuth;
 301     }
 302 #endif
 303     if( rc==SQLITE_OK ) rc = initData.rc;
 304     sqlite3DbFree(db, zSql);
 305 #ifndef SQLITE_OMIT_ANALYZE
 306     if( rc==SQLITE_OK ){
 307       sqlite3AnalysisLoad(db, iDb);
 308     }
 309 #endif
 310   }
 311   if( db->mallocFailed ){
 312     rc = SQLITE_NOMEM_BKPT;
 313     sqlite3ResetAllSchemasOfConnection(db);
 314   }
 315   if( rc==SQLITE_OK || (db->flags&SQLITE_WriteSchema)){
 316     /* Black magic: If the SQLITE_WriteSchema flag is set, then consider
 317     ** the schema loaded, even if errors occurred. In this situation the
 318     ** current sqlite3_prepare() operation will fail, but the following one
 319     ** will attempt to compile the supplied statement against whatever subset
 320     ** of the schema was loaded before the error occurred. The primary
 321     ** purpose of this is to allow access to the sqlite_master table
 322     ** even when its contents have been corrupted.
 323     */
 324     DbSetProperty(db, iDb, DB_SchemaLoaded);
 325     rc = SQLITE_OK;
 326   }
 327
 328   /* Jump here for an error that occurs after successfully allocating
 329   ** curMain and calling sqlite3BtreeEnter(). For an error that occurs
 330   ** before that point, jump to error_out.
 331   */
 332 initone_error_out:
 333   if( openedTransaction ){
 334     sqlite3BtreeCommit(pDb->pBt);
 335   }
 336   sqlite3BtreeLeave(pDb->pBt);
 337
 338 error_out:
 339   if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
 340     sqlite3OomFault(db);
 341   }
 342   return rc;
 343 }
 344
 345 /*
 346 ** Initialize all database files - the main database file, the file
 347 ** used to store temporary tables, and any additional database files
 348 ** created using ATTACH statements.  Return a success code.  If an
 349 ** error occurs, write an error message into *pzErrMsg.
 350 **
 351 ** After a database is initialized, the DB_SchemaLoaded bit is set
 352 ** bit is set in the flags field of the Db structure. If the database
 353 ** file was of zero-length, then the DB_Empty flag is also set.
 354 */
 355 int sqlite3Init(sqlite3 *db, char **pzErrMsg){
 356   int i, rc;
 357   int commit_internal = !(db->flags&SQLITE_InternChanges);
 358
 359   assert( sqlite3_mutex_held(db->mutex) );
 360   assert( sqlite3BtreeHoldsMutex(db->aDb[0].pBt) );
 361   assert( db->init.busy==0 );
 362   rc = SQLITE_OK;
 363   db->init.busy = 1;
 364   ENC(db) = SCHEMA_ENC(db);
 365   for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
 366     if( DbHasProperty(db, i, DB_SchemaLoaded) || i==1 ) continue;
 367     rc = sqlite3InitOne(db, i, pzErrMsg);
 368     if( rc ){
 369       sqlite3ResetOneSchema(db, i);
 370     }
 371   }
 372
 373   /* Once all the other databases have been initialized, load the schema
 374   ** for the TEMP database. This is loaded last, as the TEMP database
 375   ** schema may contain references to objects in other databases.
 376   */
 377 #ifndef SQLITE_OMIT_TEMPDB
 378   assert( db->nDb>1 );
 379   if( rc==SQLITE_OK && !DbHasProperty(db, 1, DB_SchemaLoaded) ){
 380     rc = sqlite3InitOne(db, 1, pzErrMsg);
 381     if( rc ){
 382       sqlite3ResetOneSchema(db, 1);
 383     }
 384   }
 385 #endif
 386
 387   db->init.busy = 0;
 388   if( rc==SQLITE_OK && commit_internal ){
 389     sqlite3CommitInternalChanges(db);
 390   }
 391
 392   return rc;
 393 }
 394
 395 /*
 396 ** This routine is a no-op if the database schema is already initialized.
 397 ** Otherwise, the schema is loaded. An error code is returned.
 398 */
 399 int sqlite3ReadSchema(Parse *pParse){
 400   int rc = SQLITE_OK;
 401   sqlite3 *db = pParse->db;
 402   assert( sqlite3_mutex_held(db->mutex) );
 403   if( !db->init.busy ){
 404     rc = sqlite3Init(db, &pParse->zErrMsg);
 405   }
 406   if( rc!=SQLITE_OK ){
 407     pParse->rc = rc;
 408     pParse->nErr++;
 409   }
 410   return rc;
 411 }
 412
 413
 414 /*
 415 ** Check schema cookies in all databases.  If any cookie is out
 416 ** of date set pParse->rc to SQLITE_SCHEMA.  If all schema cookies
 417 ** make no changes to pParse->rc.
 418 */
 419 static void schemaIsValid(Parse *pParse){
 420   sqlite3 *db = pParse->db;
 421   int iDb;
 422   int rc;
 423   int cookie;
 424
 425   assert( pParse->checkSchema );
 426   assert( sqlite3_mutex_held(db->mutex) );
 427   for(iDb=0; iDb<db->nDb; iDb++){
 428     int openedTransaction = 0;         /* True if a transaction is opened */
 429     Btree *pBt = db->aDb[iDb].pBt;     /* Btree database to read cookie from */
 430     if( pBt==0 ) continue;
 431
 432     /* If there is not already a read-only (or read-write) transaction opened
 433     ** on the b-tree database, open one now. If a transaction is opened, it
 434     ** will be closed immediately after reading the meta-value. */
 435     if( !sqlite3BtreeIsInReadTrans(pBt) ){
 436       rc = sqlite3BtreeBeginTrans(pBt, 0);
 437       if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
 438         sqlite3OomFault(db);
 439       }
 440       if( rc!=SQLITE_OK ) return;
 441       openedTransaction = 1;
 442     }
 443
 444     /* Read the schema cookie from the database. If it does not match the
 445     ** value stored as part of the in-memory schema representation,
 446     ** set Parse.rc to SQLITE_SCHEMA. */
 447     sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&cookie);
 448     assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
 449     if( cookie!=db->aDb[iDb].pSchema->schema_cookie ){
 450       sqlite3ResetOneSchema(db, iDb);
 451       pParse->rc = SQLITE_SCHEMA;
 452     }
 453
 454     /* Close the transaction, if one was opened. */
 455     if( openedTransaction ){
 456       sqlite3BtreeCommit(pBt);
 457     }
 458   }
 459 }
 460
 461 /*
 462 ** Convert a schema pointer into the iDb index that indicates
 463 ** which database file in db->aDb[] the schema refers to.
 464 **
 465 ** If the same database is attached more than once, the first
 466 ** attached database is returned.
 467 */
 468 int sqlite3SchemaToIndex(sqlite3 *db, Schema *pSchema){
 469   int i = -1000000;
 470
 471   /* If pSchema is NULL, then return -1000000. This happens when code in
 472   ** expr.c is trying to resolve a reference to a transient table (i.e. one
 473   ** created by a sub-select). In this case the return value of this
 474   ** function should never be used.
 475   **
 476   ** We return -1000000 instead of the more usual -1 simply because using
 477   ** -1000000 as the incorrect index into db->aDb[] is much
 478   ** more likely to cause a segfault than -1 (of course there are assert()
 479   ** statements too, but it never hurts to play the odds).
 480   */
 481   assert( sqlite3_mutex_held(db->mutex) );
 482   if( pSchema ){
 483     for(i=0; ALWAYS(i<db->nDb); i++){
 484       if( db->aDb[i].pSchema==pSchema ){
 485         break;
 486       }
 487     }
 488     assert( i>=0 && i<db->nDb );
 489   }
 490   return i;
 491 }
 492
 493 /*
 494 ** Free all memory allocations in the pParse object
 495 */
 496 void sqlite3ParserReset(Parse *pParse){
 497   if( pParse ){
 498     sqlite3 *db = pParse->db;
 499     sqlite3DbFree(db, pParse->aLabel);
 500     sqlite3ExprListDelete(db, pParse->pConstExpr);
 501     if( db ){
 502       assert( db->lookaside.bDisable >= pParse->disableLookaside );
 503       db->lookaside.bDisable -= pParse->disableLookaside;
 504     }
 505     pParse->disableLookaside = 0;
 506   }
 507 }
 508
 509 /*
 510 ** Compile the UTF-8 encoded SQL statement zSql into a statement handle.
 511 */
 512 static int sqlite3Prepare(
 513   sqlite3 *db,              /* Database handle. */
 514   const char *zSql,         /* UTF-8 encoded SQL statement. */
 515   int nBytes,               /* Length of zSql in bytes. */
 516   u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
 517   Vdbe *pReprepare,         /* VM being reprepared */
 518   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 519   const char **pzTail       /* OUT: End of parsed string */
 520 ){
 521   char *zErrMsg = 0;        /* Error message */
 522   int rc = SQLITE_OK;       /* Result code */
 523   int i;                    /* Loop counter */
 524   Parse sParse;             /* Parsing context */
 525
 526   memset(&sParse, 0, PARSE_HDR_SZ);
 527   memset(PARSE_TAIL(&sParse), 0, PARSE_TAIL_SZ);
 528   sParse.pReprepare = pReprepare;
 529   assert( ppStmt && *ppStmt==0 );
 530   /* assert( !db->mallocFailed ); // not true with SQLITE_USE_ALLOCA */
 531   assert( sqlite3_mutex_held(db->mutex) );
 532
 533   /* For a long-term use prepared statement avoid the use of
 534   ** lookaside memory.
 535   */
 536   if( prepFlags & SQLITE_PREPARE_PERSISTENT ){
 537     sParse.disableLookaside++;
 538     db->lookaside.bDisable++;
 539   }
 540
 541   /* Check to verify that it is possible to get a read lock on all
 542   ** database schemas.  The inability to get a read lock indicates that
 543   ** some other database connection is holding a write-lock, which in
 544   ** turn means that the other connection has made uncommitted changes
 545   ** to the schema.
 546   **
 547   ** Were we to proceed and prepare the statement against the uncommitted
 548   ** schema changes and if those schema changes are subsequently rolled
 549   ** back and different changes are made in their place, then when this
 550   ** prepared statement goes to run the schema cookie would fail to detect
 551   ** the schema change.  Disaster would follow.
 552   **
 553   ** This thread is currently holding mutexes on all Btrees (because
 554   ** of the sqlite3BtreeEnterAll() in sqlite3LockAndPrepare()) so it
 555   ** is not possible for another thread to start a new schema change
 556   ** while this routine is running.  Hence, we do not need to hold
 557   ** locks on the schema, we just need to make sure nobody else is
 558   ** holding them.
 559   **
 560   ** Note that setting READ_UNCOMMITTED overrides most lock detection,
 561   ** but it does *not* override schema lock detection, so this all still
 562   ** works even if READ_UNCOMMITTED is set.
 563   */
 564   for(i=0; i<db->nDb; i++) {
 565     Btree *pBt = db->aDb[i].pBt;
 566     if( pBt ){
 567       assert( sqlite3BtreeHoldsMutex(pBt) );
 568       rc = sqlite3BtreeSchemaLocked(pBt);
 569       if( rc ){
 570         const char *zDb = db->aDb[i].zDbSName;
 571         sqlite3ErrorWithMsg(db, rc, "database schema is locked: %s", zDb);
 572         testcase( db->flags & SQLITE_ReadUncommit );
 573         goto end_prepare;
 574       }
 575     }
 576   }
 577
 578   sqlite3VtabUnlockList(db);
 579
 580   sParse.db = db;
 581   if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){
 582     char *zSqlCopy;
 583     int mxLen = db->aLimit[SQLITE_LIMIT_SQL_LENGTH];
 584     testcase( nBytes==mxLen );
 585     testcase( nBytes==mxLen+1 );
 586     if( nBytes>mxLen ){
 587       sqlite3ErrorWithMsg(db, SQLITE_TOOBIG, "statement too long");
 588       rc = sqlite3ApiExit(db, SQLITE_TOOBIG);
 589       goto end_prepare;
 590     }
 591     zSqlCopy = sqlite3DbStrNDup(db, zSql, nBytes);
 592     if( zSqlCopy ){
 593       sqlite3RunParser(&sParse, zSqlCopy, &zErrMsg);
 594       sParse.zTail = &zSql[sParse.zTail-zSqlCopy];
 595       sqlite3DbFree(db, zSqlCopy);
 596     }else{
 597       sParse.zTail = &zSql[nBytes];
 598     }
 599   }else{
 600     sqlite3RunParser(&sParse, zSql, &zErrMsg);
 601   }
 602   assert( 0==sParse.nQueryLoop );
 603
 604   if( sParse.rc==SQLITE_DONE ) sParse.rc = SQLITE_OK;
 605   if( sParse.checkSchema ){
 606     schemaIsValid(&sParse);
 607   }
 608   if( db->mallocFailed ){
 609     sParse.rc = SQLITE_NOMEM_BKPT;
 610   }
 611   if( pzTail ){
 612     *pzTail = sParse.zTail;
 613   }
 614   rc = sParse.rc;
 615
 616 #ifndef SQLITE_OMIT_EXPLAIN
 617   if( rc==SQLITE_OK && sParse.pVdbe && sParse.explain ){
 618     static const char * const azColName[] = {
 619        "addr", "opcode", "p1", "p2", "p3", "p4", "p5", "comment",
 620        "selectid", "order", "from", "detail"
 621     };
 622     int iFirst, mx;
 623     if( sParse.explain==2 ){
 624       sqlite3VdbeSetNumCols(sParse.pVdbe, 4);
 625       iFirst = 8;
 626       mx = 12;
 627     }else{
 628       sqlite3VdbeSetNumCols(sParse.pVdbe, 8);
 629       iFirst = 0;
 630       mx = 8;
 631     }
 632     for(i=iFirst; i<mx; i++){
 633       sqlite3VdbeSetColName(sParse.pVdbe, i-iFirst, COLNAME_NAME,
 634                             azColName[i], SQLITE_STATIC);
 635     }
 636   }
 637 #endif
 638
 639   if( db->init.busy==0 ){
 640     sqlite3VdbeSetSql(sParse.pVdbe, zSql, (int)(sParse.zTail-zSql), prepFlags);
 641   }
 642   if( sParse.pVdbe && (rc!=SQLITE_OK || db->mallocFailed) ){
 643     sqlite3VdbeFinalize(sParse.pVdbe);
 644     assert(!(*ppStmt));
 645   }else{
 646     *ppStmt = (sqlite3_stmt*)sParse.pVdbe;
 647   }
 648
 649   if( zErrMsg ){
 650     sqlite3ErrorWithMsg(db, rc, "%s", zErrMsg);
 651     sqlite3DbFree(db, zErrMsg);
 652   }else{
 653     sqlite3Error(db, rc);
 654   }
 655
 656   /* Delete any TriggerPrg structures allocated while parsing this statement. */
 657   while( sParse.pTriggerPrg ){
 658     TriggerPrg *pT = sParse.pTriggerPrg;
 659     sParse.pTriggerPrg = pT->pNext;
 660     sqlite3DbFree(db, pT);
 661   }
 662
 663 end_prepare:
 664
 665   sqlite3ParserReset(&sParse);
 666   rc = sqlite3ApiExit(db, rc);
 667   assert( (rc&db->errMask)==rc );
 668   return rc;
 669 }
 670 static int sqlite3LockAndPrepare(
 671   sqlite3 *db,              /* Database handle. */
 672   const char *zSql,         /* UTF-8 encoded SQL statement. */
 673   int nBytes,               /* Length of zSql in bytes. */
 674   u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
 675   Vdbe *pOld,               /* VM being reprepared */
 676   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 677   const char **pzTail       /* OUT: End of parsed string */
 678 ){
 679   int rc;
 680
 681 #ifdef SQLITE_ENABLE_API_ARMOR
 682   if( ppStmt==0 ) return SQLITE_MISUSE_BKPT;
 683 #endif
 684   *ppStmt = 0;
 685   if( !sqlite3SafetyCheckOk(db)||zSql==0 ){
 686     return SQLITE_MISUSE_BKPT;
 687   }
 688   sqlite3_mutex_enter(db->mutex);
 689   sqlite3BtreeEnterAll(db);
 690   rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
 691   if( rc==SQLITE_SCHEMA ){
 692     sqlite3_finalize(*ppStmt);
 693     rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
 694   }
 695   sqlite3BtreeLeaveAll(db);
 696   sqlite3_mutex_leave(db->mutex);
 697   assert( rc==SQLITE_OK || *ppStmt==0 );
 698   return rc;
 699 }
 700
 701 /*
 702 ** Rerun the compilation of a statement after a schema change.
 703 **
 704 ** If the statement is successfully recompiled, return SQLITE_OK. Otherwise,
 705 ** if the statement cannot be recompiled because another connection has
 706 ** locked the sqlite3_master table, return SQLITE_LOCKED. If any other error
 707 ** occurs, return SQLITE_SCHEMA.
 708 */
 709 int sqlite3Reprepare(Vdbe *p){
 710   int rc;
 711   sqlite3_stmt *pNew;
 712   const char *zSql;
 713   sqlite3 *db;
 714   u8 prepFlags;
 715
 716   assert( sqlite3_mutex_held(sqlite3VdbeDb(p)->mutex) );
 717   zSql = sqlite3_sql((sqlite3_stmt *)p);
 718   assert( zSql!=0 );  /* Reprepare only called for prepare_v2() statements */
 719   db = sqlite3VdbeDb(p);
 720   assert( sqlite3_mutex_held(db->mutex) );
 721   prepFlags = sqlite3VdbePrepareFlags(p);
 722   rc = sqlite3LockAndPrepare(db, zSql, -1, prepFlags, p, &pNew, 0);
 723   if( rc ){
 724     if( rc==SQLITE_NOMEM ){
 725       sqlite3OomFault(db);
 726     }
 727     assert( pNew==0 );
 728     return rc;
 729   }else{
 730     assert( pNew!=0 );
 731   }
 732   sqlite3VdbeSwap((Vdbe*)pNew, p);
 733   sqlite3TransferBindings(pNew, (sqlite3_stmt*)p);
 734   sqlite3VdbeResetStepResult((Vdbe*)pNew);
 735   sqlite3VdbeFinalize((Vdbe*)pNew);
 736   return SQLITE_OK;
 737 }
 738
 739
 740 /*
 741 ** Two versions of the official API.  Legacy and new use.  In the legacy
 742 ** version, the original SQL text is not saved in the prepared statement
 743 ** and so if a schema change occurs, SQLITE_SCHEMA is returned by
 744 ** sqlite3_step().  In the new version, the original SQL text is retained
 745 ** and the statement is automatically recompiled if an schema change
 746 ** occurs.
 747 */
 748 int sqlite3_prepare(
 749   sqlite3 *db,              /* Database handle. */
 750   const char *zSql,         /* UTF-8 encoded SQL statement. */
 751   int nBytes,               /* Length of zSql in bytes. */
 752   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 753   const char **pzTail       /* OUT: End of parsed string */
 754 ){
 755   int rc;
 756   rc = sqlite3LockAndPrepare(db,zSql,nBytes,0,0,ppStmt,pzTail);
 757   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
 758   return rc;
 759 }
 760 int sqlite3_prepare_v2(
 761   sqlite3 *db,              /* Database handle. */
 762   const char *zSql,         /* UTF-8 encoded SQL statement. */
 763   int nBytes,               /* Length of zSql in bytes. */
 764   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 765   const char **pzTail       /* OUT: End of parsed string */
 766 ){
 767   int rc;
 768   /* EVIDENCE-OF: R-37923-12173 The sqlite3_prepare_v2() interface works
 769   ** exactly the same as sqlite3_prepare_v3() with a zero prepFlags
 770   ** parameter.
 771   **
 772   ** Proof in that the 5th parameter to sqlite3LockAndPrepare is 0 */
 773   rc = sqlite3LockAndPrepare(db,zSql,nBytes,SQLITE_PREPARE_SAVESQL,0,
 774                              ppStmt,pzTail);
 775   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );
 776   return rc;
 777 }
 778 int sqlite3_prepare_v3(
 779   sqlite3 *db,              /* Database handle. */
 780   const char *zSql,         /* UTF-8 encoded SQL statement. */
 781   int nBytes,               /* Length of zSql in bytes. */
 782   unsigned int prepFlags,   /* Zero or more SQLITE_PREPARE_* flags */
 783   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 784   const char **pzTail       /* OUT: End of parsed string */
 785 ){
 786   int rc;
 787   /* EVIDENCE-OF: R-56861-42673 sqlite3_prepare_v3() differs from
 788   ** sqlite3_prepare_v2() only in having the extra prepFlags parameter,
 789   ** which is a bit array consisting of zero or more of the
 790   ** SQLITE_PREPARE_* flags.
 791   **
 792   ** Proof by comparison to the implementation of sqlite3_prepare_v2()
 793   ** directly above. */
 794   rc = sqlite3LockAndPrepare(db,zSql,nBytes,
 795                  SQLITE_PREPARE_SAVESQL|(prepFlags&SQLITE_PREPARE_MASK),
 796                  0,ppStmt,pzTail);
 797   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );
 798   return rc;
 799 }
 800
 801
 802 #ifndef SQLITE_OMIT_UTF16
 803 /*
 804 ** Compile the UTF-16 encoded SQL statement zSql into a statement handle.
 805 */
 806 static int sqlite3Prepare16(
 807   sqlite3 *db,              /* Database handle. */
 808   const void *zSql,         /* UTF-16 encoded SQL statement. */
 809   int nBytes,               /* Length of zSql in bytes. */
 810   u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
 811   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 812   const void **pzTail       /* OUT: End of parsed string */
 813 ){
 814   /* This function currently works by first transforming the UTF-16
 815   ** encoded string to UTF-8, then invoking sqlite3_prepare(). The
 816   ** tricky bit is figuring out the pointer to return in *pzTail.
 817   */
 818   char *zSql8;
 819   const char *zTail8 = 0;
 820   int rc = SQLITE_OK;
 821
 822 #ifdef SQLITE_ENABLE_API_ARMOR
 823   if( ppStmt==0 ) return SQLITE_MISUSE_BKPT;
 824 #endif
 825   *ppStmt = 0;
 826   if( !sqlite3SafetyCheckOk(db)||zSql==0 ){
 827     return SQLITE_MISUSE_BKPT;
 828   }
 829   if( nBytes>=0 ){
 830     int sz;
 831     const char *z = (const char*)zSql;
 832     for(sz=0; sz<nBytes && (z[sz]!=0 || z[sz+1]!=0); sz += 2){}
 833     nBytes = sz;
 834   }
 835   sqlite3_mutex_enter(db->mutex);
 836   zSql8 = sqlite3Utf16to8(db, zSql, nBytes, SQLITE_UTF16NATIVE);
 837   if( zSql8 ){
 838     rc = sqlite3LockAndPrepare(db, zSql8, -1, prepFlags, 0, ppStmt, &zTail8);
 839   }
 840
 841   if( zTail8 && pzTail ){
 842     /* If sqlite3_prepare returns a tail pointer, we calculate the
 843     ** equivalent pointer into the UTF-16 string by counting the unicode
 844     ** characters between zSql8 and zTail8, and then returning a pointer
 845     ** the same number of characters into the UTF-16 string.
 846     */
 847     int chars_parsed = sqlite3Utf8CharLen(zSql8, (int)(zTail8-zSql8));
 848     *pzTail = (u8 *)zSql + sqlite3Utf16ByteLen(zSql, chars_parsed);
 849   }
 850   sqlite3DbFree(db, zSql8);
 851   rc = sqlite3ApiExit(db, rc);
 852   sqlite3_mutex_leave(db->mutex);
 853   return rc;
 854 }
 855
 856 /*
 857 ** Two versions of the official API.  Legacy and new use.  In the legacy
 858 ** version, the original SQL text is not saved in the prepared statement
 859 ** and so if a schema change occurs, SQLITE_SCHEMA is returned by
 860 ** sqlite3_step().  In the new version, the original SQL text is retained
 861 ** and the statement is automatically recompiled if an schema change
 862 ** occurs.
 863 */
 864 int sqlite3_prepare16(
 865   sqlite3 *db,              /* Database handle. */
 866   const void *zSql,         /* UTF-16 encoded SQL statement. */
 867   int nBytes,               /* Length of zSql in bytes. */
 868   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 869   const void **pzTail       /* OUT: End of parsed string */
 870 ){
 871   int rc;
 872   rc = sqlite3Prepare16(db,zSql,nBytes,0,ppStmt,pzTail);
 873   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
 874   return rc;
 875 }
 876 int sqlite3_prepare16_v2(
 877   sqlite3 *db,              /* Database handle. */
 878   const void *zSql,         /* UTF-16 encoded SQL statement. */
 879   int nBytes,               /* Length of zSql in bytes. */
 880   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 881   const void **pzTail       /* OUT: End of parsed string */
 882 ){
 883   int rc;
 884   rc = sqlite3Prepare16(db,zSql,nBytes,SQLITE_PREPARE_SAVESQL,ppStmt,pzTail);
 885   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
 886   return rc;
 887 }
 888 int sqlite3_prepare16_v3(
 889   sqlite3 *db,              /* Database handle. */
 890   const void *zSql,         /* UTF-16 encoded SQL statement. */
 891   int nBytes,               /* Length of zSql in bytes. */
 892   unsigned int prepFlags,   /* Zero or more SQLITE_PREPARE_* flags */
 893   sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
 894   const void **pzTail       /* OUT: End of parsed string */
 895 ){
 896   int rc;
 897   rc = sqlite3Prepare16(db,zSql,nBytes,
 898          SQLITE_PREPARE_SAVESQL|(prepFlags&SQLITE_PREPARE_MASK),
 899          ppStmt,pzTail);
 900   assert( rc==SQLITE_OK || ppStmt==0 || *ppStmt==0 );  /* VERIFY: F13021 */
 901   return rc;
 902 }
 903
 904 #endif /* SQLITE_OMIT_UTF16 */