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