src/alter.c

   1 /*
   2 ** 2005 February 15
   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 C code routines that used to generate VDBE code
  13 ** that implements the ALTER TABLE command.
  14 */
  15 #include "sqliteInt.h"
  16
  17 /*
  18 ** The code in this file only exists if we are not omitting the
  19 ** ALTER TABLE logic from the build.
  20 */
  21 #ifndef SQLITE_OMIT_ALTERTABLE
  22
  23
  24 /*
  25 ** This function is used by SQL generated to implement the
  26 ** ALTER TABLE command. The first argument is the text of a CREATE TABLE or
  27 ** CREATE INDEX command. The second is a table name. The table name in
  28 ** the CREATE TABLE or CREATE INDEX statement is replaced with the third
  29 ** argument and the result returned. Examples:
  30 **
  31 ** sqlite_rename_table('CREATE TABLE abc(a, b, c)', 'def')
  32 **     -> 'CREATE TABLE def(a, b, c)'
  33 **
  34 ** sqlite_rename_table('CREATE INDEX i ON abc(a)', 'def')
  35 **     -> 'CREATE INDEX i ON def(a, b, c)'
  36 */
  37 static void renameTableFunc(
  38   sqlite3_context *context,
  39   int NotUsed,
  40   sqlite3_value **argv
  41 ){
  42   unsigned char const *zSql = sqlite3_value_text(argv[0]);
  43   unsigned char const *zTableName = sqlite3_value_text(argv[1]);
  44
  45   int token;
  46   Token tname;
  47   unsigned char const *zCsr = zSql;
  48   int len = 0;
  49   char *zRet;
  50
  51   sqlite3 *db = sqlite3_context_db_handle(context);
  52
  53   UNUSED_PARAMETER(NotUsed);
  54
  55   /* The principle used to locate the table name in the CREATE TABLE
  56   ** statement is that the table name is the first non-space token that
  57   ** is immediately followed by a TK_LP or TK_USING token.
  58   */
  59   if( zSql ){
  60     do {
  61       if( !*zCsr ){
  62         /* Ran out of input before finding an opening bracket. Return NULL. */
  63         return;
  64       }
  65
  66       /* Store the token that zCsr points to in tname. */
  67       tname.z = (char*)zCsr;
  68       tname.n = len;
  69
  70       /* Advance zCsr to the next token. Store that token type in 'token',
  71       ** and its length in 'len' (to be used next iteration of this loop).
  72       */
  73       do {
  74         zCsr += len;
  75         len = sqlite3GetToken(zCsr, &token);
  76       } while( token==TK_SPACE );
  77       assert( len>0 );
  78     } while( token!=TK_LP && token!=TK_USING );
  79
  80     zRet = sqlite3MPrintf(db, "%.*s\"%w\"%s", (int)(((u8*)tname.z) - zSql),
  81        zSql, zTableName, tname.z+tname.n);
  82     sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);
  83   }
  84 }
  85
  86 /*
  87 ** This C function implements an SQL user function that is used by SQL code
  88 ** generated by the ALTER TABLE ... RENAME command to modify the definition
  89 ** of any foreign key constraints that use the table being renamed as the
  90 ** parent table. It is passed three arguments:
  91 **
  92 **   1) The complete text of the CREATE TABLE statement being modified,
  93 **   2) The old name of the table being renamed, and
  94 **   3) The new name of the table being renamed.
  95 **
  96 ** It returns the new CREATE TABLE statement. For example:
  97 **
  98 **   sqlite_rename_parent('CREATE TABLE t1(a REFERENCES t2)', 't2', 't3')
  99 **       -> 'CREATE TABLE t1(a REFERENCES t3)'
 100 */
 101 #ifndef SQLITE_OMIT_FOREIGN_KEY
 102 static void renameParentFunc(
 103   sqlite3_context *context,
 104   int NotUsed,
 105   sqlite3_value **argv
 106 ){
 107   sqlite3 *db = sqlite3_context_db_handle(context);
 108   char *zOutput = 0;
 109   char *zResult;
 110   unsigned char const *zInput = sqlite3_value_text(argv[0]);
 111   unsigned char const *zOld = sqlite3_value_text(argv[1]);
 112   unsigned char const *zNew = sqlite3_value_text(argv[2]);
 113
 114   unsigned const char *z;         /* Pointer to token */
 115   int n;                          /* Length of token z */
 116   int token;                      /* Type of token */
 117
 118   UNUSED_PARAMETER(NotUsed);
 119   if( zInput==0 || zOld==0 ) return;
 120   for(z=zInput; *z; z=z+n){
 121     n = sqlite3GetToken(z, &token);
 122     if( token==TK_REFERENCES ){
 123       char *zParent;
 124       do {
 125         z += n;
 126         n = sqlite3GetToken(z, &token);
 127       }while( token==TK_SPACE );
 128
 129       if( token==TK_ILLEGAL ) break;
 130       zParent = sqlite3DbStrNDup(db, (const char *)z, n);
 131       if( zParent==0 ) break;
 132       sqlite3Dequote(zParent);
 133       if( 0==sqlite3StrICmp((const char *)zOld, zParent) ){
 134         char *zOut = sqlite3MPrintf(db, "%s%.*s\"%w\"",
 135             (zOutput?zOutput:""), (int)(z-zInput), zInput, (const char *)zNew
 136         );
 137         sqlite3DbFree(db, zOutput);
 138         zOutput = zOut;
 139         zInput = &z[n];
 140       }
 141       sqlite3DbFree(db, zParent);
 142     }
 143   }
 144
 145   zResult = sqlite3MPrintf(db, "%s%s", (zOutput?zOutput:""), zInput);
 146   sqlite3_result_text(context, zResult, -1, SQLITE_DYNAMIC);
 147   sqlite3DbFree(db, zOutput);
 148 }
 149 #endif
 150
 151 #ifndef SQLITE_OMIT_TRIGGER
 152 /* This function is used by SQL generated to implement the
 153 ** ALTER TABLE command. The first argument is the text of a CREATE TRIGGER
 154 ** statement. The second is a table name. The table name in the CREATE
 155 ** TRIGGER statement is replaced with the third argument and the result
 156 ** returned. This is analagous to renameTableFunc() above, except for CREATE
 157 ** TRIGGER, not CREATE INDEX and CREATE TABLE.
 158 */
 159 static void renameTriggerFunc(
 160   sqlite3_context *context,
 161   int NotUsed,
 162   sqlite3_value **argv
 163 ){
 164   unsigned char const *zSql = sqlite3_value_text(argv[0]);
 165   unsigned char const *zTableName = sqlite3_value_text(argv[1]);
 166
 167   int token;
 168   Token tname;
 169   int dist = 3;
 170   unsigned char const *zCsr = zSql;
 171   int len = 0;
 172   char *zRet;
 173   sqlite3 *db = sqlite3_context_db_handle(context);
 174
 175   UNUSED_PARAMETER(NotUsed);
 176
 177   /* The principle used to locate the table name in the CREATE TRIGGER
 178   ** statement is that the table name is the first token that is immediately
 179   ** preceded by either TK_ON or TK_DOT and immediately followed by one
 180   ** of TK_WHEN, TK_BEGIN or TK_FOR.
 181   */
 182   if( zSql ){
 183     do {
 184
 185       if( !*zCsr ){
 186         /* Ran out of input before finding the table name. Return NULL. */
 187         return;
 188       }
 189
 190       /* Store the token that zCsr points to in tname. */
 191       tname.z = (char*)zCsr;
 192       tname.n = len;
 193
 194       /* Advance zCsr to the next token. Store that token type in 'token',
 195       ** and its length in 'len' (to be used next iteration of this loop).
 196       */
 197       do {
 198         zCsr += len;
 199         len = sqlite3GetToken(zCsr, &token);
 200       }while( token==TK_SPACE );
 201       assert( len>0 );
 202
 203       /* Variable 'dist' stores the number of tokens read since the most
 204       ** recent TK_DOT or TK_ON. This means that when a WHEN, FOR or BEGIN
 205       ** token is read and 'dist' equals 2, the condition stated above
 206       ** to be met.
 207       **
 208       ** Note that ON cannot be a database, table or column name, so
 209       ** there is no need to worry about syntax like
 210       ** "CREATE TRIGGER ... ON ON.ON BEGIN ..." etc.
 211       */
 212       dist++;
 213       if( token==TK_DOT || token==TK_ON ){
 214         dist = 0;
 215       }
 216     } while( dist!=2 || (token!=TK_WHEN && token!=TK_FOR && token!=TK_BEGIN) );
 217
 218     /* Variable tname now contains the token that is the old table-name
 219     ** in the CREATE TRIGGER statement.
 220     */
 221     zRet = sqlite3MPrintf(db, "%.*s\"%w\"%s", (int)(((u8*)tname.z) - zSql),
 222        zSql, zTableName, tname.z+tname.n);
 223     sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);
 224   }
 225 }
 226 #endif   /* !SQLITE_OMIT_TRIGGER */
 227
 228 /*
 229 ** Register built-in functions used to help implement ALTER TABLE
 230 */
 231 void sqlite3AlterFunctions(void){
 232   static FuncDef aAlterTableFuncs[] = {
 233     FUNCTION(sqlite_rename_table,   2, 0, 0, renameTableFunc),
 234 #ifndef SQLITE_OMIT_TRIGGER
 235     FUNCTION(sqlite_rename_trigger, 2, 0, 0, renameTriggerFunc),
 236 #endif
 237 #ifndef SQLITE_OMIT_FOREIGN_KEY
 238     FUNCTION(sqlite_rename_parent,  3, 0, 0, renameParentFunc),
 239 #endif
 240   };
 241   sqlite3InsertBuiltinFuncs(aAlterTableFuncs, ArraySize(aAlterTableFuncs));
 242 }
 243
 244 /*
 245 ** This function is used to create the text of expressions of the form:
 246 **
 247 **   name=<constant1> OR name=<constant2> OR ...
 248 **
 249 ** If argument zWhere is NULL, then a pointer string containing the text
 250 ** "name=<constant>" is returned, where <constant> is the quoted version
 251 ** of the string passed as argument zConstant. The returned buffer is
 252 ** allocated using sqlite3DbMalloc(). It is the responsibility of the
 253 ** caller to ensure that it is eventually freed.
 254 **
 255 ** If argument zWhere is not NULL, then the string returned is
 256 ** "<where> OR name=<constant>", where <where> is the contents of zWhere.
 257 ** In this case zWhere is passed to sqlite3DbFree() before returning.
 258 **
 259 */
 260 static char *whereOrName(sqlite3 *db, char *zWhere, char *zConstant){
 261   char *zNew;
 262   if( !zWhere ){
 263     zNew = sqlite3MPrintf(db, "name=%Q", zConstant);
 264   }else{
 265     zNew = sqlite3MPrintf(db, "%s OR name=%Q", zWhere, zConstant);
 266     sqlite3DbFree(db, zWhere);
 267   }
 268   return zNew;
 269 }
 270
 271 #if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
 272 /*
 273 ** Generate the text of a WHERE expression which can be used to select all
 274 ** tables that have foreign key constraints that refer to table pTab (i.e.
 275 ** constraints for which pTab is the parent table) from the sqlite_master
 276 ** table.
 277 */
 278 static char *whereForeignKeys(Parse *pParse, Table *pTab){
 279   FKey *p;
 280   char *zWhere = 0;
 281   for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
 282     zWhere = whereOrName(pParse->db, zWhere, p->pFrom->zName);
 283   }
 284   return zWhere;
 285 }
 286 #endif
 287
 288 /*
 289 ** Generate the text of a WHERE expression which can be used to select all
 290 ** temporary triggers on table pTab from the sqlite_temp_master table. If
 291 ** table pTab has no temporary triggers, or is itself stored in the
 292 ** temporary database, NULL is returned.
 293 */
 294 static char *whereTempTriggers(Parse *pParse, Table *pTab){
 295   Trigger *pTrig;
 296   char *zWhere = 0;
 297   const Schema *pTempSchema = pParse->db->aDb[1].pSchema; /* Temp db schema */
 298
 299   /* If the table is not located in the temp-db (in which case NULL is
 300   ** returned, loop through the tables list of triggers. For each trigger
 301   ** that is not part of the temp-db schema, add a clause to the WHERE
 302   ** expression being built up in zWhere.
 303   */
 304   if( pTab->pSchema!=pTempSchema ){
 305     sqlite3 *db = pParse->db;
 306     for(pTrig=sqlite3TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
 307       if( pTrig->pSchema==pTempSchema ){
 308         zWhere = whereOrName(db, zWhere, pTrig->zName);
 309       }
 310     }
 311   }
 312   if( zWhere ){
 313     char *zNew = sqlite3MPrintf(pParse->db, "type='trigger' AND (%s)", zWhere);
 314     sqlite3DbFree(pParse->db, zWhere);
 315     zWhere = zNew;
 316   }
 317   return zWhere;
 318 }
 319
 320 /*
 321 ** Generate code to drop and reload the internal representation of table
 322 ** pTab from the database, including triggers and temporary triggers.
 323 ** Argument zName is the name of the table in the database schema at
 324 ** the time the generated code is executed. This can be different from
 325 ** pTab->zName if this function is being called to code part of an
 326 ** "ALTER TABLE RENAME TO" statement.
 327 */
 328 static void reloadTableSchema(Parse *pParse, Table *pTab, const char *zName){
 329   Vdbe *v;
 330   char *zWhere;
 331   int iDb;                   /* Index of database containing pTab */
 332 #ifndef SQLITE_OMIT_TRIGGER
 333   Trigger *pTrig;
 334 #endif
 335
 336   v = sqlite3GetVdbe(pParse);
 337   if( NEVER(v==0) ) return;
 338   assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
 339   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
 340   assert( iDb>=0 );
 341
 342 #ifndef SQLITE_OMIT_TRIGGER
 343   /* Drop any table triggers from the internal schema. */
 344   for(pTrig=sqlite3TriggerList(pParse, pTab); pTrig; pTrig=pTrig->pNext){
 345     int iTrigDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
 346     assert( iTrigDb==iDb || iTrigDb==1 );
 347     sqlite3VdbeAddOp4(v, OP_DropTrigger, iTrigDb, 0, 0, pTrig->zName, 0);
 348   }
 349 #endif
 350
 351   /* Drop the table and index from the internal schema.  */
 352   sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);
 353
 354   /* Reload the table, index and permanent trigger schemas. */
 355   zWhere = sqlite3MPrintf(pParse->db, "tbl_name=%Q", zName);
 356   if( !zWhere ) return;
 357   sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere);
 358
 359 #ifndef SQLITE_OMIT_TRIGGER
 360   /* Now, if the table is not stored in the temp database, reload any temp
 361   ** triggers. Don't use IN(...) in case SQLITE_OMIT_SUBQUERY is defined.
 362   */
 363   if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){
 364     sqlite3VdbeAddParseSchemaOp(v, 1, zWhere);
 365   }
 366 #endif
 367 }
 368
 369 /*
 370 ** Parameter zName is the name of a table that is about to be altered
 371 ** (either with ALTER TABLE ... RENAME TO or ALTER TABLE ... ADD COLUMN).
 372 ** If the table is a system table, this function leaves an error message
 373 ** in pParse->zErr (system tables may not be altered) and returns non-zero.
 374 **
 375 ** Or, if zName is not a system table, zero is returned.
 376 */
 377 static int isSystemTable(Parse *pParse, const char *zName){
 378   if( 0==sqlite3StrNICmp(zName, "sqlite_", 7) ){
 379     sqlite3ErrorMsg(pParse, "table %s may not be altered", zName);
 380     return 1;
 381   }
 382   return 0;
 383 }
 384
 385 /*
 386 ** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy"
 387 ** command.
 388 */
 389 void sqlite3AlterRenameTable(
 390   Parse *pParse,            /* Parser context. */
 391   SrcList *pSrc,            /* The table to rename. */
 392   Token *pName              /* The new table name. */
 393 ){
 394   int iDb;                  /* Database that contains the table */
 395   char *zDb;                /* Name of database iDb */
 396   Table *pTab;              /* Table being renamed */
 397   char *zName = 0;          /* NULL-terminated version of pName */
 398   sqlite3 *db = pParse->db; /* Database connection */
 399   int nTabName;             /* Number of UTF-8 characters in zTabName */
 400   const char *zTabName;     /* Original name of the table */
 401   Vdbe *v;
 402 #ifndef SQLITE_OMIT_TRIGGER
 403   char *zWhere = 0;         /* Where clause to locate temp triggers */
 404 #endif
 405   VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
 406   u32 savedDbFlags;         /* Saved value of db->mDbFlags */
 407
 408   savedDbFlags = db->mDbFlags;
 409   if( NEVER(db->mallocFailed) ) goto exit_rename_table;
 410   assert( pSrc->nSrc==1 );
 411   assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
 412
 413   pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
 414   if( !pTab ) goto exit_rename_table;
 415   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
 416   zDb = db->aDb[iDb].zDbSName;
 417   db->mDbFlags |= DBFLAG_PreferBuiltin;
 418
 419   /* Get a NULL terminated version of the new table name. */
 420   zName = sqlite3NameFromToken(db, pName);
 421   if( !zName ) goto exit_rename_table;
 422
 423   /* Check that a table or index named 'zName' does not already exist
 424   ** in database iDb. If so, this is an error.
 425   */
 426   if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){
 427     sqlite3ErrorMsg(pParse,
 428         "there is already another table or index with this name: %s", zName);
 429     goto exit_rename_table;
 430   }
 431
 432   /* Make sure it is not a system table being altered, or a reserved name
 433   ** that the table is being renamed to.
 434   */
 435   if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ){
 436     goto exit_rename_table;
 437   }
 438   if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){ goto
 439     exit_rename_table;
 440   }
 441
 442 #ifndef SQLITE_OMIT_VIEW
 443   if( pTab->pSelect ){
 444     sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);
 445     goto exit_rename_table;
 446   }
 447 #endif
 448
 449 #ifndef SQLITE_OMIT_AUTHORIZATION
 450   /* Invoke the authorization callback. */
 451   if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
 452     goto exit_rename_table;
 453   }
 454 #endif
 455
 456 #ifndef SQLITE_OMIT_VIRTUALTABLE
 457   if( sqlite3ViewGetColumnNames(pParse, pTab) ){
 458     goto exit_rename_table;
 459   }
 460   if( IsVirtual(pTab) ){
 461     pVTab = sqlite3GetVTable(db, pTab);
 462     if( pVTab->pVtab->pModule->xRename==0 ){
 463       pVTab = 0;
 464     }
 465   }
 466 #endif
 467
 468   /* Begin a transaction for database iDb.
 469   ** Then modify the schema cookie (since the ALTER TABLE modifies the
 470   ** schema). Open a statement transaction if the table is a virtual
 471   ** table.
 472   */
 473   v = sqlite3GetVdbe(pParse);
 474   if( v==0 ){
 475     goto exit_rename_table;
 476   }
 477   sqlite3BeginWriteOperation(pParse, pVTab!=0, iDb);
 478   sqlite3ChangeCookie(pParse, iDb);
 479
 480   /* If this is a virtual table, invoke the xRename() function if
 481   ** one is defined. The xRename() callback will modify the names
 482   ** of any resources used by the v-table implementation (including other
 483   ** SQLite tables) that are identified by the name of the virtual table.
 484   */
 485 #ifndef SQLITE_OMIT_VIRTUALTABLE
 486   if( pVTab ){
 487     int i = ++pParse->nMem;
 488     sqlite3VdbeLoadString(v, i, zName);
 489     sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pVTab, P4_VTAB);
 490     sqlite3MayAbort(pParse);
 491   }
 492 #endif
 493
 494   /* figure out how many UTF-8 characters are in zName */
 495   zTabName = pTab->zName;
 496   nTabName = sqlite3Utf8CharLen(zTabName, -1);
 497
 498 #if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
 499   if( db->flags&SQLITE_ForeignKeys ){
 500     /* If foreign-key support is enabled, rewrite the CREATE TABLE
 501     ** statements corresponding to all child tables of foreign key constraints
 502     ** for which the renamed table is the parent table.  */
 503     if( (zWhere=whereForeignKeys(pParse, pTab))!=0 ){
 504       sqlite3NestedParse(pParse,
 505           "UPDATE \"%w\".%s SET "
 506               "sql = sqlite_rename_parent(sql, %Q, %Q) "
 507               "WHERE %s;", zDb, MASTER_NAME, zTabName, zName, zWhere);
 508       sqlite3DbFree(db, zWhere);
 509     }
 510   }
 511 #endif
 512
 513   /* Modify the sqlite_master table to use the new table name. */
 514   sqlite3NestedParse(pParse,
 515       "UPDATE %Q.%s SET "
 516 #ifdef SQLITE_OMIT_TRIGGER
 517           "sql = sqlite_rename_table(sql, %Q), "
 518 #else
 519           "sql = CASE "
 520             "WHEN type = 'trigger' THEN sqlite_rename_trigger(sql, %Q)"
 521             "ELSE sqlite_rename_table(sql, %Q) END, "
 522 #endif
 523           "tbl_name = %Q, "
 524           "name = CASE "
 525             "WHEN type='table' THEN %Q "
 526             "WHEN name LIKE 'sqlite_autoindex%%' AND type='index' THEN "
 527              "'sqlite_autoindex_' || %Q || substr(name,%d+18) "
 528             "ELSE name END "
 529       "WHERE tbl_name=%Q COLLATE nocase AND "
 530           "(type='table' OR type='index' OR type='trigger');",
 531       zDb, MASTER_NAME, zName, zName, zName,
 532 #ifndef SQLITE_OMIT_TRIGGER
 533       zName,
 534 #endif
 535       zName, nTabName, zTabName
 536   );
 537
 538 #ifndef SQLITE_OMIT_AUTOINCREMENT
 539   /* If the sqlite_sequence table exists in this database, then update
 540   ** it with the new table name.
 541   */
 542   if( sqlite3FindTable(db, "sqlite_sequence", zDb) ){
 543     sqlite3NestedParse(pParse,
 544         "UPDATE \"%w\".sqlite_sequence set name = %Q WHERE name = %Q",
 545         zDb, zName, pTab->zName);
 546   }
 547 #endif
 548
 549 #ifndef SQLITE_OMIT_TRIGGER
 550   /* If there are TEMP triggers on this table, modify the sqlite_temp_master
 551   ** table. Don't do this if the table being ALTERed is itself located in
 552   ** the temp database.
 553   */
 554   if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){
 555     sqlite3NestedParse(pParse,
 556         "UPDATE sqlite_temp_master SET "
 557             "sql = sqlite_rename_trigger(sql, %Q), "
 558             "tbl_name = %Q "
 559             "WHERE %s;", zName, zName, zWhere);
 560     sqlite3DbFree(db, zWhere);
 561   }
 562 #endif
 563
 564 #if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
 565   if( db->flags&SQLITE_ForeignKeys ){
 566     FKey *p;
 567     for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
 568       Table *pFrom = p->pFrom;
 569       if( pFrom!=pTab ){
 570         reloadTableSchema(pParse, p->pFrom, pFrom->zName);
 571       }
 572     }
 573   }
 574 #endif
 575
 576   /* Drop and reload the internal table schema. */
 577   reloadTableSchema(pParse, pTab, zName);
 578
 579 exit_rename_table:
 580   sqlite3SrcListDelete(db, pSrc);
 581   sqlite3DbFree(db, zName);
 582   db->mDbFlags = savedDbFlags;
 583 }
 584
 585 /*
 586 ** This function is called after an "ALTER TABLE ... ADD" statement
 587 ** has been parsed. Argument pColDef contains the text of the new
 588 ** column definition.
 589 **
 590 ** The Table structure pParse->pNewTable was extended to include
 591 ** the new column during parsing.
 592 */
 593 void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
 594   Table *pNew;              /* Copy of pParse->pNewTable */
 595   Table *pTab;              /* Table being altered */
 596   int iDb;                  /* Database number */
 597   const char *zDb;          /* Database name */
 598   const char *zTab;         /* Table name */
 599   char *zCol;               /* Null-terminated column definition */
 600   Column *pCol;             /* The new column */
 601   Expr *pDflt;              /* Default value for the new column */
 602   sqlite3 *db;              /* The database connection; */
 603   Vdbe *v = pParse->pVdbe;  /* The prepared statement under construction */
 604   int r1;                   /* Temporary registers */
 605
 606   db = pParse->db;
 607   if( pParse->nErr || db->mallocFailed ) return;
 608   assert( v!=0 );
 609   pNew = pParse->pNewTable;
 610   assert( pNew );
 611
 612   assert( sqlite3BtreeHoldsAllMutexes(db) );
 613   iDb = sqlite3SchemaToIndex(db, pNew->pSchema);
 614   zDb = db->aDb[iDb].zDbSName;
 615   zTab = &pNew->zName[16];  /* Skip the "sqlite_altertab_" prefix on the name */
 616   pCol = &pNew->aCol[pNew->nCol-1];
 617   pDflt = pCol->pDflt;
 618   pTab = sqlite3FindTable(db, zTab, zDb);
 619   assert( pTab );
 620
 621 #ifndef SQLITE_OMIT_AUTHORIZATION
 622   /* Invoke the authorization callback. */
 623   if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
 624     return;
 625   }
 626 #endif
 627
 628   /* If the default value for the new column was specified with a
 629   ** literal NULL, then set pDflt to 0. This simplifies checking
 630   ** for an SQL NULL default below.
 631   */
 632   assert( pDflt==0 || pDflt->op==TK_SPAN );
 633   if( pDflt && pDflt->pLeft->op==TK_NULL ){
 634     pDflt = 0;
 635   }
 636
 637   /* Check that the new column is not specified as PRIMARY KEY or UNIQUE.
 638   ** If there is a NOT NULL constraint, then the default value for the
 639   ** column must not be NULL.
 640   */
 641   if( pCol->colFlags & COLFLAG_PRIMKEY ){
 642     sqlite3ErrorMsg(pParse, "Cannot add a PRIMARY KEY column");
 643     return;
 644   }
 645   if( pNew->pIndex ){
 646     sqlite3ErrorMsg(pParse, "Cannot add a UNIQUE column");
 647     return;
 648   }
 649   if( (db->flags&SQLITE_ForeignKeys) && pNew->pFKey && pDflt ){
 650     sqlite3ErrorMsg(pParse,
 651         "Cannot add a REFERENCES column with non-NULL default value");
 652     return;
 653   }
 654   if( pCol->notNull && !pDflt ){
 655     sqlite3ErrorMsg(pParse,
 656         "Cannot add a NOT NULL column with default value NULL");
 657     return;
 658   }
 659
 660   /* Ensure the default expression is something that sqlite3ValueFromExpr()
 661   ** can handle (i.e. not CURRENT_TIME etc.)
 662   */
 663   if( pDflt ){
 664     sqlite3_value *pVal = 0;
 665     int rc;
 666     rc = sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_BLOB, &pVal);
 667     assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
 668     if( rc!=SQLITE_OK ){
 669       assert( db->mallocFailed == 1 );
 670       return;
 671     }
 672     if( !pVal ){
 673       sqlite3ErrorMsg(pParse, "Cannot add a column with non-constant default");
 674       return;
 675     }
 676     sqlite3ValueFree(pVal);
 677   }
 678
 679   /* Modify the CREATE TABLE statement. */
 680   zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);
 681   if( zCol ){
 682     char *zEnd = &zCol[pColDef->n-1];
 683     u32 savedDbFlags = db->mDbFlags;
 684     while( zEnd>zCol && (*zEnd==';' || sqlite3Isspace(*zEnd)) ){
 685       *zEnd-- = '\0';
 686     }
 687     db->mDbFlags |= DBFLAG_PreferBuiltin;
 688     sqlite3NestedParse(pParse,
 689         "UPDATE \"%w\".%s SET "
 690           "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "
 691         "WHERE type = 'table' AND name = %Q",
 692       zDb, MASTER_NAME, pNew->addColOffset, zCol, pNew->addColOffset+1,
 693       zTab
 694     );
 695     sqlite3DbFree(db, zCol);
 696     db->mDbFlags = savedDbFlags;
 697   }
 698
 699   /* Make sure the schema version is at least 3.  But do not upgrade
 700   ** from less than 3 to 4, as that will corrupt any preexisting DESC
 701   ** index.
 702   */
 703   r1 = sqlite3GetTempReg(pParse);
 704   sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, r1, BTREE_FILE_FORMAT);
 705   sqlite3VdbeUsesBtree(v, iDb);
 706   sqlite3VdbeAddOp2(v, OP_AddImm, r1, -2);
 707   sqlite3VdbeAddOp2(v, OP_IfPos, r1, sqlite3VdbeCurrentAddr(v)+2);
 708   VdbeCoverage(v);
 709   sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, 3);
 710   sqlite3ReleaseTempReg(pParse, r1);
 711
 712   /* Reload the schema of the modified table. */
 713   reloadTableSchema(pParse, pTab, pTab->zName);
 714 }
 715
 716 /*
 717 ** This function is called by the parser after the table-name in
 718 ** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument
 719 ** pSrc is the full-name of the table being altered.
 720 **
 721 ** This routine makes a (partial) copy of the Table structure
 722 ** for the table being altered and sets Parse.pNewTable to point
 723 ** to it. Routines called by the parser as the column definition
 724 ** is parsed (i.e. sqlite3AddColumn()) add the new Column data to
 725 ** the copy. The copy of the Table structure is deleted by tokenize.c
 726 ** after parsing is finished.
 727 **
 728 ** Routine sqlite3AlterFinishAddColumn() will be called to complete
 729 ** coding the "ALTER TABLE ... ADD" statement.
 730 */
 731 void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){
 732   Table *pNew;
 733   Table *pTab;
 734   Vdbe *v;
 735   int iDb;
 736   int i;
 737   int nAlloc;
 738   sqlite3 *db = pParse->db;
 739
 740   /* Look up the table being altered. */
 741   assert( pParse->pNewTable==0 );
 742   assert( sqlite3BtreeHoldsAllMutexes(db) );
 743   if( db->mallocFailed ) goto exit_begin_add_column;
 744   pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
 745   if( !pTab ) goto exit_begin_add_column;
 746
 747 #ifndef SQLITE_OMIT_VIRTUALTABLE
 748   if( IsVirtual(pTab) ){
 749     sqlite3ErrorMsg(pParse, "virtual tables may not be altered");
 750     goto exit_begin_add_column;
 751   }
 752 #endif
 753
 754   /* Make sure this is not an attempt to ALTER a view. */
 755   if( pTab->pSelect ){
 756     sqlite3ErrorMsg(pParse, "Cannot add a column to a view");
 757     goto exit_begin_add_column;
 758   }
 759   if( SQLITE_OK!=isSystemTable(pParse, pTab->zName) ){
 760     goto exit_begin_add_column;
 761   }
 762
 763   assert( pTab->addColOffset>0 );
 764   iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
 765
 766   /* Put a copy of the Table struct in Parse.pNewTable for the
 767   ** sqlite3AddColumn() function and friends to modify.  But modify
 768   ** the name by adding an "sqlite_altertab_" prefix.  By adding this
 769   ** prefix, we insure that the name will not collide with an existing
 770   ** table because user table are not allowed to have the "sqlite_"
 771   ** prefix on their name.
 772   */
 773   pNew = (Table*)sqlite3DbMallocZero(db, sizeof(Table));
 774   if( !pNew ) goto exit_begin_add_column;
 775   pParse->pNewTable = pNew;
 776   pNew->nTabRef = 1;
 777   pNew->nCol = pTab->nCol;
 778   assert( pNew->nCol>0 );
 779   nAlloc = (((pNew->nCol-1)/8)*8)+8;
 780   assert( nAlloc>=pNew->nCol && nAlloc%8==0 && nAlloc-pNew->nCol<8 );
 781   pNew->aCol = (Column*)sqlite3DbMallocZero(db, sizeof(Column)*nAlloc);
 782   pNew->zName = sqlite3MPrintf(db, "sqlite_altertab_%s", pTab->zName);
 783   if( !pNew->aCol || !pNew->zName ){
 784     assert( db->mallocFailed );
 785     goto exit_begin_add_column;
 786   }
 787   memcpy(pNew->aCol, pTab->aCol, sizeof(Column)*pNew->nCol);
 788   for(i=0; i<pNew->nCol; i++){
 789     Column *pCol = &pNew->aCol[i];
 790     pCol->zName = sqlite3DbStrDup(db, pCol->zName);
 791     pCol->zColl = 0;
 792     pCol->pDflt = 0;
 793   }
 794   pNew->pSchema = db->aDb[iDb].pSchema;
 795   pNew->addColOffset = pTab->addColOffset;
 796   pNew->nTabRef = 1;
 797
 798   /* Begin a transaction and increment the schema cookie.  */
 799   sqlite3BeginWriteOperation(pParse, 0, iDb);
 800   v = sqlite3GetVdbe(pParse);
 801   if( !v ) goto exit_begin_add_column;
 802   sqlite3ChangeCookie(pParse, iDb);
 803
 804 exit_begin_add_column:
 805   sqlite3SrcListDelete(db, pSrc);
 806   return;
 807 }
 808 #endif  /* SQLITE_ALTER_TABLE */