src/trigger.c

   1 /*
   2 **
   3 ** The author disclaims copyright to this source code.  In place of
   4 ** a legal notice, here is a blessing:
   5 **
   6 **    May you do good and not evil.
   7 **    May you find forgiveness for yourself and forgive others.
   8 **    May you share freely, never taking more than you give.
   9 **
  10 *************************************************************************
  11 ** This file contains the implementation for TRIGGERs
  12 */
  13 #include "sqliteInt.h"
  14
  15 #ifndef SQLITE_OMIT_TRIGGER
  16 /*
  17 ** Delete a linked list of TriggerStep structures.
  18 */
  19 void sqlite3DeleteTriggerStep(sqlite3 *db, TriggerStep *pTriggerStep){
  20   while( pTriggerStep ){
  21     TriggerStep * pTmp = pTriggerStep;
  22     pTriggerStep = pTriggerStep->pNext;
  23
  24     sqlite3ExprDelete(db, pTmp->pWhere);
  25     sqlite3ExprListDelete(db, pTmp->pExprList);
  26     sqlite3SelectDelete(db, pTmp->pSelect);
  27     sqlite3IdListDelete(db, pTmp->pIdList);
  28     sqlite3UpsertDelete(db, pTmp->pUpsert);
  29     sqlite3DbFree(db, pTmp->zSpan);
  30
  31     sqlite3DbFree(db, pTmp);
  32   }
  33 }
  34
  35 /*
  36 ** Given table pTab, return a list of all the triggers attached to
  37 ** the table. The list is connected by Trigger.pNext pointers.
  38 **
  39 ** All of the triggers on pTab that are in the same database as pTab
  40 ** are already attached to pTab->pTrigger.  But there might be additional
  41 ** triggers on pTab in the TEMP schema.  This routine prepends all
  42 ** TEMP triggers on pTab to the beginning of the pTab->pTrigger list
  43 ** and returns the combined list.
  44 **
  45 ** To state it another way:  This routine returns a list of all triggers
  46 ** that fire off of pTab.  The list will include any TEMP triggers on
  47 ** pTab as well as the triggers lised in pTab->pTrigger.
  48 */
  49 Trigger *sqlite3TriggerList(Parse *pParse, Table *pTab){
  50   Schema * const pTmpSchema = pParse->db->aDb[1].pSchema;
  51   Trigger *pList = 0;                  /* List of triggers to return */
  52
  53   if( pParse->disableTriggers ){
  54     return 0;
  55   }
  56
  57   if( pTmpSchema!=pTab->pSchema ){
  58     HashElem *p;
  59     assert( sqlite3SchemaMutexHeld(pParse->db, 0, pTmpSchema) );
  60     for(p=sqliteHashFirst(&pTmpSchema->trigHash); p; p=sqliteHashNext(p)){
  61       Trigger *pTrig = (Trigger *)sqliteHashData(p);
  62       if( pTrig->pTabSchema==pTab->pSchema
  63        && 0==sqlite3StrICmp(pTrig->table, pTab->zName)
  64       ){
  65         pTrig->pNext = (pList ? pList : pTab->pTrigger);
  66         pList = pTrig;
  67       }
  68     }
  69   }
  70
  71   return (pList ? pList : pTab->pTrigger);
  72 }
  73
  74 /*
  75 ** This is called by the parser when it sees a CREATE TRIGGER statement
  76 ** up to the point of the BEGIN before the trigger actions.  A Trigger
  77 ** structure is generated based on the information available and stored
  78 ** in pParse->pNewTrigger.  After the trigger actions have been parsed, the
  79 ** sqlite3FinishTrigger() function is called to complete the trigger
  80 ** construction process.
  81 */
  82 void sqlite3BeginTrigger(
  83   Parse *pParse,      /* The parse context of the CREATE TRIGGER statement */
  84   Token *pName1,      /* The name of the trigger */
  85   Token *pName2,      /* The name of the trigger */
  86   int tr_tm,          /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD */
  87   int op,             /* One of TK_INSERT, TK_UPDATE, TK_DELETE */
  88   IdList *pColumns,   /* column list if this is an UPDATE OF trigger */
  89   SrcList *pTableName,/* The name of the table/view the trigger applies to */
  90   Expr *pWhen,        /* WHEN clause */
  91   int isTemp,         /* True if the TEMPORARY keyword is present */
  92   int noErr           /* Suppress errors if the trigger already exists */
  93 ){
  94   Trigger *pTrigger = 0;  /* The new trigger */
  95   Table *pTab;            /* Table that the trigger fires off of */
  96   char *zName = 0;        /* Name of the trigger */
  97   sqlite3 *db = pParse->db;  /* The database connection */
  98   int iDb;                /* The database to store the trigger in */
  99   Token *pName;           /* The unqualified db name */
 100   DbFixer sFix;           /* State vector for the DB fixer */
 101
 102   assert( pName1!=0 );   /* pName1->z might be NULL, but not pName1 itself */
 103   assert( pName2!=0 );
 104   assert( op==TK_INSERT || op==TK_UPDATE || op==TK_DELETE );
 105   assert( op>0 && op<0xff );
 106   if( isTemp ){
 107     /* If TEMP was specified, then the trigger name may not be qualified. */
 108     if( pName2->n>0 ){
 109       sqlite3ErrorMsg(pParse, "temporary trigger may not have qualified name");
 110       goto trigger_cleanup;
 111     }
 112     iDb = 1;
 113     pName = pName1;
 114   }else{
 115     /* Figure out the db that the trigger will be created in */
 116     iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
 117     if( iDb<0 ){
 118       goto trigger_cleanup;
 119     }
 120   }
 121   if( !pTableName || db->mallocFailed ){
 122     goto trigger_cleanup;
 123   }
 124
 125   /* A long-standing parser bug is that this syntax was allowed:
 126   **
 127   **    CREATE TRIGGER attached.demo AFTER INSERT ON attached.tab ....
 128   **                                                 ^^^^^^^^
 129   **
 130   ** To maintain backwards compatibility, ignore the database
 131   ** name on pTableName if we are reparsing out of SQLITE_MASTER.
 132   */
 133   if( db->init.busy && iDb!=1 ){
 134     sqlite3DbFree(db, pTableName->a[0].zDatabase);
 135     pTableName->a[0].zDatabase = 0;
 136   }
 137
 138   /* If the trigger name was unqualified, and the table is a temp table,
 139   ** then set iDb to 1 to create the trigger in the temporary database.
 140   ** If sqlite3SrcListLookup() returns 0, indicating the table does not
 141   ** exist, the error is caught by the block below.
 142   */
 143   pTab = sqlite3SrcListLookup(pParse, pTableName);
 144   if( db->init.busy==0 && pName2->n==0 && pTab
 145         && pTab->pSchema==db->aDb[1].pSchema ){
 146     iDb = 1;
 147   }
 148
 149   /* Ensure the table name matches database name and that the table exists */
 150   if( db->mallocFailed ) goto trigger_cleanup;
 151   assert( pTableName->nSrc==1 );
 152   sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName);
 153   if( sqlite3FixSrcList(&sFix, pTableName) ){
 154     goto trigger_cleanup;
 155   }
 156   pTab = sqlite3SrcListLookup(pParse, pTableName);
 157   if( !pTab ){
 158     /* The table does not exist. */
 159     if( db->init.iDb==1 ){
 160       /* Ticket #3810.
 161       ** Normally, whenever a table is dropped, all associated triggers are
 162       ** dropped too.  But if a TEMP trigger is created on a non-TEMP table
 163       ** and the table is dropped by a different database connection, the
 164       ** trigger is not visible to the database connection that does the
 165       ** drop so the trigger cannot be dropped.  This results in an
 166       ** "orphaned trigger" - a trigger whose associated table is missing.
 167       */
 168       db->init.orphanTrigger = 1;
 169     }
 170     goto trigger_cleanup;
 171   }
 172   if( IsVirtual(pTab) ){
 173     sqlite3ErrorMsg(pParse, "cannot create triggers on virtual tables");
 174     goto trigger_cleanup;
 175   }
 176
 177   /* Check that the trigger name is not reserved and that no trigger of the
 178   ** specified name exists */
 179   zName = sqlite3NameFromToken(db, pName);
 180   if( zName==0 ){
 181     assert( db->mallocFailed );
 182     goto trigger_cleanup;
 183   }
 184   if( sqlite3CheckObjectName(pParse, zName, "trigger", pTab->zName) ){
 185     goto trigger_cleanup;
 186   }
 187   assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
 188   if( !IN_RENAME_OBJECT ){
 189     if( sqlite3HashFind(&(db->aDb[iDb].pSchema->trigHash),zName) ){
 190       if( !noErr ){
 191         sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);
 192       }else{
 193         assert( !db->init.busy );
 194         sqlite3CodeVerifySchema(pParse, iDb);
 195       }
 196       goto trigger_cleanup;
 197     }
 198   }
 199
 200   /* Do not create a trigger on a system table */
 201   if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
 202     sqlite3ErrorMsg(pParse, "cannot create trigger on system table");
 203     goto trigger_cleanup;
 204   }
 205
 206   /* INSTEAD of triggers are only for views and views only support INSTEAD
 207   ** of triggers.
 208   */
 209   if( pTab->pSelect && tr_tm!=TK_INSTEAD ){
 210     sqlite3ErrorMsg(pParse, "cannot create %s trigger on view: %S",
 211         (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName, 0);
 212     goto trigger_cleanup;
 213   }
 214   if( !pTab->pSelect && tr_tm==TK_INSTEAD ){
 215     sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"
 216         " trigger on table: %S", pTableName, 0);
 217     goto trigger_cleanup;
 218   }
 219
 220 #ifndef SQLITE_OMIT_AUTHORIZATION
 221   if( !IN_RENAME_OBJECT ){
 222     int iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
 223     int code = SQLITE_CREATE_TRIGGER;
 224     const char *zDb = db->aDb[iTabDb].zDbSName;
 225     const char *zDbTrig = isTemp ? db->aDb[1].zDbSName : zDb;
 226     if( iTabDb==1 || isTemp ) code = SQLITE_CREATE_TEMP_TRIGGER;
 227     if( sqlite3AuthCheck(pParse, code, zName, pTab->zName, zDbTrig) ){
 228       goto trigger_cleanup;
 229     }
 230     if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(iTabDb),0,zDb)){
 231       goto trigger_cleanup;
 232     }
 233   }
 234 #endif
 235
 236   /* INSTEAD OF triggers can only appear on views and BEFORE triggers
 237   ** cannot appear on views.  So we might as well translate every
 238   ** INSTEAD OF trigger into a BEFORE trigger.  It simplifies code
 239   ** elsewhere.
 240   */
 241   if (tr_tm == TK_INSTEAD){
 242     tr_tm = TK_BEFORE;
 243   }
 244
 245   /* Build the Trigger object */
 246   pTrigger = (Trigger*)sqlite3DbMallocZero(db, sizeof(Trigger));
 247   if( pTrigger==0 ) goto trigger_cleanup;
 248   pTrigger->zName = zName;
 249   zName = 0;
 250   pTrigger->table = sqlite3DbStrDup(db, pTableName->a[0].zName);
 251   pTrigger->pSchema = db->aDb[iDb].pSchema;
 252   pTrigger->pTabSchema = pTab->pSchema;
 253   pTrigger->op = (u8)op;
 254   pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;
 255   if( IN_RENAME_OBJECT ){
 256     sqlite3RenameTokenRemap(pParse, pTrigger->table, pTableName->a[0].zName);
 257     pTrigger->pWhen = pWhen;
 258     pWhen = 0;
 259   }else{
 260     pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
 261   }
 262   pTrigger->pColumns = pColumns;
 263   pColumns = 0;
 264   assert( pParse->pNewTrigger==0 );
 265   pParse->pNewTrigger = pTrigger;
 266
 267 trigger_cleanup:
 268   sqlite3DbFree(db, zName);
 269   sqlite3SrcListDelete(db, pTableName);
 270   sqlite3IdListDelete(db, pColumns);
 271   sqlite3ExprDelete(db, pWhen);
 272   if( !pParse->pNewTrigger ){
 273     sqlite3DeleteTrigger(db, pTrigger);
 274   }else{
 275     assert( pParse->pNewTrigger==pTrigger );
 276   }
 277 }
 278
 279 /*
 280 ** This routine is called after all of the trigger actions have been parsed
 281 ** in order to complete the process of building the trigger.
 282 */
 283 void sqlite3FinishTrigger(
 284   Parse *pParse,          /* Parser context */
 285   TriggerStep *pStepList, /* The triggered program */
 286   Token *pAll             /* Token that describes the complete CREATE TRIGGER */
 287 ){
 288   Trigger *pTrig = pParse->pNewTrigger;   /* Trigger being finished */
 289   char *zName;                            /* Name of trigger */
 290   sqlite3 *db = pParse->db;               /* The database */
 291   DbFixer sFix;                           /* Fixer object */
 292   int iDb;                                /* Database containing the trigger */
 293   Token nameToken;                        /* Trigger name for error reporting */
 294
 295   pParse->pNewTrigger = 0;
 296   if( NEVER(pParse->nErr) || !pTrig ) goto triggerfinish_cleanup;
 297   zName = pTrig->zName;
 298   iDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
 299   pTrig->step_list = pStepList;
 300   while( pStepList ){
 301     pStepList->pTrig = pTrig;
 302     pStepList = pStepList->pNext;
 303   }
 304   sqlite3TokenInit(&nameToken, pTrig->zName);
 305   sqlite3FixInit(&sFix, pParse, iDb, "trigger", &nameToken);
 306   if( sqlite3FixTriggerStep(&sFix, pTrig->step_list)
 307    || sqlite3FixExpr(&sFix, pTrig->pWhen)
 308   ){
 309     goto triggerfinish_cleanup;
 310   }
 311
 312 #ifndef SQLITE_OMIT_ALTERTABLE
 313   if( IN_RENAME_OBJECT ){
 314     assert( !db->init.busy );
 315     pParse->pNewTrigger = pTrig;
 316     pTrig = 0;
 317   }else
 318 #endif
 319
 320   /* if we are not initializing,
 321   ** build the sqlite_master entry
 322   */
 323   if( !db->init.busy ){
 324     Vdbe *v;
 325     char *z;
 326
 327     /* Make an entry in the sqlite_master table */
 328     v = sqlite3GetVdbe(pParse);
 329     if( v==0 ) goto triggerfinish_cleanup;
 330     sqlite3BeginWriteOperation(pParse, 0, iDb);
 331     z = sqlite3DbStrNDup(db, (char*)pAll->z, pAll->n);
 332     testcase( z==0 );
 333     sqlite3NestedParse(pParse,
 334        "INSERT INTO %Q.%s VALUES('trigger',%Q,%Q,0,'CREATE TRIGGER %q')",
 335        db->aDb[iDb].zDbSName, MASTER_NAME, zName,
 336        pTrig->table, z);
 337     sqlite3DbFree(db, z);
 338     sqlite3ChangeCookie(pParse, iDb);
 339     sqlite3VdbeAddParseSchemaOp(v, iDb,
 340         sqlite3MPrintf(db, "type='trigger' AND name='%q'", zName));
 341   }
 342
 343   if( db->init.busy ){
 344     Trigger *pLink = pTrig;
 345     Hash *pHash = &db->aDb[iDb].pSchema->trigHash;
 346     assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
 347     assert( pLink!=0 );
 348     pTrig = sqlite3HashInsert(pHash, zName, pTrig);
 349     if( pTrig ){
 350       sqlite3OomFault(db);
 351     }else if( pLink->pSchema==pLink->pTabSchema ){
 352       Table *pTab;
 353       pTab = sqlite3HashFind(&pLink->pTabSchema->tblHash, pLink->table);
 354       assert( pTab!=0 );
 355       pLink->pNext = pTab->pTrigger;
 356       pTab->pTrigger = pLink;
 357     }
 358   }
 359
 360 triggerfinish_cleanup:
 361   sqlite3DeleteTrigger(db, pTrig);
 362   assert( IN_RENAME_OBJECT || !pParse->pNewTrigger );
 363   sqlite3DeleteTriggerStep(db, pStepList);
 364 }
 365
 366 /*
 367 ** Duplicate a range of text from an SQL statement, then convert all
 368 ** whitespace characters into ordinary space characters.
 369 */
 370 static char *triggerSpanDup(sqlite3 *db, const char *zStart, const char *zEnd){
 371   char *z = sqlite3DbSpanDup(db, zStart, zEnd);
 372   int i;
 373   if( z ) for(i=0; z[i]; i++) if( sqlite3Isspace(z[i]) ) z[i] = ' ';
 374   return z;
 375 }
 376
 377 /*
 378 ** Turn a SELECT statement (that the pSelect parameter points to) into
 379 ** a trigger step.  Return a pointer to a TriggerStep structure.
 380 **
 381 ** The parser calls this routine when it finds a SELECT statement in
 382 ** body of a TRIGGER.
 383 */
 384 TriggerStep *sqlite3TriggerSelectStep(
 385   sqlite3 *db,                /* Database connection */
 386   Select *pSelect,            /* The SELECT statement */
 387   const char *zStart,         /* Start of SQL text */
 388   const char *zEnd            /* End of SQL text */
 389 ){
 390   TriggerStep *pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep));
 391   if( pTriggerStep==0 ) {
 392     sqlite3SelectDelete(db, pSelect);
 393     return 0;
 394   }
 395   pTriggerStep->op = TK_SELECT;
 396   pTriggerStep->pSelect = pSelect;
 397   pTriggerStep->orconf = OE_Default;
 398   pTriggerStep->zSpan = triggerSpanDup(db, zStart, zEnd);
 399   return pTriggerStep;
 400 }
 401
 402 /*
 403 ** Allocate space to hold a new trigger step.  The allocated space
 404 ** holds both the TriggerStep object and the TriggerStep.target.z string.
 405 **
 406 ** If an OOM error occurs, NULL is returned and db->mallocFailed is set.
 407 */
 408 static TriggerStep *triggerStepAllocate(
 409   Parse *pParse,              /* Parser context */
 410   u8 op,                      /* Trigger opcode */
 411   Token *pName,               /* The target name */
 412   const char *zStart,         /* Start of SQL text */
 413   const char *zEnd            /* End of SQL text */
 414 ){
 415   sqlite3 *db = pParse->db;
 416   TriggerStep *pTriggerStep;
 417
 418   pTriggerStep = sqlite3DbMallocZero(db, sizeof(TriggerStep) + pName->n + 1);
 419   if( pTriggerStep ){
 420     char *z = (char*)&pTriggerStep[1];
 421     memcpy(z, pName->z, pName->n);
 422     sqlite3Dequote(z);
 423     pTriggerStep->zTarget = z;
 424     pTriggerStep->op = op;
 425     pTriggerStep->zSpan = triggerSpanDup(db, zStart, zEnd);
 426     if( IN_RENAME_OBJECT ){
 427       sqlite3RenameTokenMap(pParse, pTriggerStep->zTarget, pName);
 428     }
 429   }
 430   return pTriggerStep;
 431 }
 432
 433 /*
 434 ** Build a trigger step out of an INSERT statement.  Return a pointer
 435 ** to the new trigger step.
 436 **
 437 ** The parser calls this routine when it sees an INSERT inside the
 438 ** body of a trigger.
 439 */
 440 TriggerStep *sqlite3TriggerInsertStep(
 441   Parse *pParse,      /* Parser */
 442   Token *pTableName,  /* Name of the table into which we insert */
 443   IdList *pColumn,    /* List of columns in pTableName to insert into */
 444   Select *pSelect,    /* A SELECT statement that supplies values */
 445   u8 orconf,          /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */
 446   Upsert *pUpsert,    /* ON CONFLICT clauses for upsert */
 447   const char *zStart, /* Start of SQL text */
 448   const char *zEnd    /* End of SQL text */
 449 ){
 450   sqlite3 *db = pParse->db;
 451   TriggerStep *pTriggerStep;
 452
 453   assert(pSelect != 0 || db->mallocFailed);
 454
 455   pTriggerStep = triggerStepAllocate(pParse, TK_INSERT, pTableName,zStart,zEnd);
 456   if( pTriggerStep ){
 457     if( IN_RENAME_OBJECT ){
 458       pTriggerStep->pSelect = pSelect;
 459       pSelect = 0;
 460     }else{
 461       pTriggerStep->pSelect = sqlite3SelectDup(db, pSelect, EXPRDUP_REDUCE);
 462     }
 463     pTriggerStep->pIdList = pColumn;
 464     pTriggerStep->pUpsert = pUpsert;
 465     pTriggerStep->orconf = orconf;
 466     if( pUpsert ){
 467       sqlite3HasExplicitNulls(pParse, pUpsert->pUpsertTarget);
 468     }
 469   }else{
 470     testcase( pColumn );
 471     sqlite3IdListDelete(db, pColumn);
 472     testcase( pUpsert );
 473     sqlite3UpsertDelete(db, pUpsert);
 474   }
 475   sqlite3SelectDelete(db, pSelect);
 476
 477   return pTriggerStep;
 478 }
 479
 480 /*
 481 ** Construct a trigger step that implements an UPDATE statement and return
 482 ** a pointer to that trigger step.  The parser calls this routine when it
 483 ** sees an UPDATE statement inside the body of a CREATE TRIGGER.
 484 */
 485 TriggerStep *sqlite3TriggerUpdateStep(
 486   Parse *pParse,          /* Parser */
 487   Token *pTableName,   /* Name of the table to be updated */
 488   ExprList *pEList,    /* The SET clause: list of column and new values */
 489   Expr *pWhere,        /* The WHERE clause */
 490   u8 orconf,           /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
 491   const char *zStart,  /* Start of SQL text */
 492   const char *zEnd     /* End of SQL text */
 493 ){
 494   sqlite3 *db = pParse->db;
 495   TriggerStep *pTriggerStep;
 496
 497   pTriggerStep = triggerStepAllocate(pParse, TK_UPDATE, pTableName,zStart,zEnd);
 498   if( pTriggerStep ){
 499     if( IN_RENAME_OBJECT ){
 500       pTriggerStep->pExprList = pEList;
 501       pTriggerStep->pWhere = pWhere;
 502       pEList = 0;
 503       pWhere = 0;
 504     }else{
 505       pTriggerStep->pExprList = sqlite3ExprListDup(db, pEList, EXPRDUP_REDUCE);
 506       pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
 507     }
 508     pTriggerStep->orconf = orconf;
 509   }
 510   sqlite3ExprListDelete(db, pEList);
 511   sqlite3ExprDelete(db, pWhere);
 512   return pTriggerStep;
 513 }
 514
 515 /*
 516 ** Construct a trigger step that implements a DELETE statement and return
 517 ** a pointer to that trigger step.  The parser calls this routine when it
 518 ** sees a DELETE statement inside the body of a CREATE TRIGGER.
 519 */
 520 TriggerStep *sqlite3TriggerDeleteStep(
 521   Parse *pParse,          /* Parser */
 522   Token *pTableName,      /* The table from which rows are deleted */
 523   Expr *pWhere,           /* The WHERE clause */
 524   const char *zStart,     /* Start of SQL text */
 525   const char *zEnd        /* End of SQL text */
 526 ){
 527   sqlite3 *db = pParse->db;
 528   TriggerStep *pTriggerStep;
 529
 530   pTriggerStep = triggerStepAllocate(pParse, TK_DELETE, pTableName,zStart,zEnd);
 531   if( pTriggerStep ){
 532     if( IN_RENAME_OBJECT ){
 533       pTriggerStep->pWhere = pWhere;
 534       pWhere = 0;
 535     }else{
 536       pTriggerStep->pWhere = sqlite3ExprDup(db, pWhere, EXPRDUP_REDUCE);
 537     }
 538     pTriggerStep->orconf = OE_Default;
 539   }
 540   sqlite3ExprDelete(db, pWhere);
 541   return pTriggerStep;
 542 }
 543
 544 /*
 545 ** Recursively delete a Trigger structure
 546 */
 547 void sqlite3DeleteTrigger(sqlite3 *db, Trigger *pTrigger){
 548   if( pTrigger==0 ) return;
 549   sqlite3DeleteTriggerStep(db, pTrigger->step_list);
 550   sqlite3DbFree(db, pTrigger->zName);
 551   sqlite3DbFree(db, pTrigger->table);
 552   sqlite3ExprDelete(db, pTrigger->pWhen);
 553   sqlite3IdListDelete(db, pTrigger->pColumns);
 554   sqlite3DbFree(db, pTrigger);
 555 }
 556
 557 /*
 558 ** This function is called to drop a trigger from the database schema.
 559 **
 560 ** This may be called directly from the parser and therefore identifies
 561 ** the trigger by name.  The sqlite3DropTriggerPtr() routine does the
 562 ** same job as this routine except it takes a pointer to the trigger
 563 ** instead of the trigger name.
 564 **/
 565 void sqlite3DropTrigger(Parse *pParse, SrcList *pName, int noErr){
 566   Trigger *pTrigger = 0;
 567   int i;
 568   const char *zDb;
 569   const char *zName;
 570   sqlite3 *db = pParse->db;
 571
 572   if( db->mallocFailed ) goto drop_trigger_cleanup;
 573   if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
 574     goto drop_trigger_cleanup;
 575   }
 576
 577   assert( pName->nSrc==1 );
 578   zDb = pName->a[0].zDatabase;
 579   zName = pName->a[0].zName;
 580   assert( zDb!=0 || sqlite3BtreeHoldsAllMutexes(db) );
 581   for(i=OMIT_TEMPDB; i<db->nDb; i++){
 582     int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
 583     if( zDb && sqlite3DbIsNamed(db, j, zDb)==0 ) continue;
 584     assert( sqlite3SchemaMutexHeld(db, j, 0) );
 585     pTrigger = sqlite3HashFind(&(db->aDb[j].pSchema->trigHash), zName);
 586     if( pTrigger ) break;
 587   }
 588   if( !pTrigger ){
 589     if( !noErr ){
 590       sqlite3ErrorMsg(pParse, "no such trigger: %S", pName, 0);
 591     }else{
 592       sqlite3CodeVerifyNamedSchema(pParse, zDb);
 593     }
 594     pParse->checkSchema = 1;
 595     goto drop_trigger_cleanup;
 596   }
 597   sqlite3DropTriggerPtr(pParse, pTrigger);
 598
 599 drop_trigger_cleanup:
 600   sqlite3SrcListDelete(db, pName);
 601 }
 602
 603 /*
 604 ** Return a pointer to the Table structure for the table that a trigger
 605 ** is set on.
 606 */
 607 static Table *tableOfTrigger(Trigger *pTrigger){
 608   return sqlite3HashFind(&pTrigger->pTabSchema->tblHash, pTrigger->table);
 609 }
 610
 611
 612 /*
 613 ** Drop a trigger given a pointer to that trigger.
 614 */
 615 void sqlite3DropTriggerPtr(Parse *pParse, Trigger *pTrigger){
 616   Table   *pTable;
 617   Vdbe *v;
 618   sqlite3 *db = pParse->db;
 619   int iDb;
 620
 621   iDb = sqlite3SchemaToIndex(pParse->db, pTrigger->pSchema);
 622   assert( iDb>=0 && iDb<db->nDb );
 623   pTable = tableOfTrigger(pTrigger);
 624   assert( (pTable && pTable->pSchema==pTrigger->pSchema) || iDb==1 );
 625 #ifndef SQLITE_OMIT_AUTHORIZATION
 626   if( pTable ){
 627     int code = SQLITE_DROP_TRIGGER;
 628     const char *zDb = db->aDb[iDb].zDbSName;
 629     const char *zTab = SCHEMA_TABLE(iDb);
 630     if( iDb==1 ) code = SQLITE_DROP_TEMP_TRIGGER;
 631     if( sqlite3AuthCheck(pParse, code, pTrigger->zName, pTable->zName, zDb) ||
 632       sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
 633       return;
 634     }
 635   }
 636 #endif
 637
 638   /* Generate code to destroy the database record of the trigger.
 639   */
 640   if( (v = sqlite3GetVdbe(pParse))!=0 ){
 641     sqlite3NestedParse(pParse,
 642        "DELETE FROM %Q.%s WHERE name=%Q AND type='trigger'",
 643        db->aDb[iDb].zDbSName, MASTER_NAME, pTrigger->zName
 644     );
 645     sqlite3ChangeCookie(pParse, iDb);
 646     sqlite3VdbeAddOp4(v, OP_DropTrigger, iDb, 0, 0, pTrigger->zName, 0);
 647   }
 648 }
 649
 650 /*
 651 ** Remove a trigger from the hash tables of the sqlite* pointer.
 652 */
 653 void sqlite3UnlinkAndDeleteTrigger(sqlite3 *db, int iDb, const char *zName){
 654   Trigger *pTrigger;
 655   Hash *pHash;
 656
 657   assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
 658   pHash = &(db->aDb[iDb].pSchema->trigHash);
 659   pTrigger = sqlite3HashInsert(pHash, zName, 0);
 660   if( ALWAYS(pTrigger) ){
 661     if( pTrigger->pSchema==pTrigger->pTabSchema ){
 662       Table *pTab = tableOfTrigger(pTrigger);
 663       if( pTab ){
 664         Trigger **pp;
 665         for(pp=&pTab->pTrigger; *pp; pp=&((*pp)->pNext)){
 666           if( *pp==pTrigger ){
 667             *pp = (*pp)->pNext;
 668             break;
 669           }
 670         }
 671       }
 672     }
 673     sqlite3DeleteTrigger(db, pTrigger);
 674     db->mDbFlags |= DBFLAG_SchemaChange;
 675   }
 676 }
 677
 678 /*
 679 ** pEList is the SET clause of an UPDATE statement.  Each entry
 680 ** in pEList is of the format <id>=<expr>.  If any of the entries
 681 ** in pEList have an <id> which matches an identifier in pIdList,
 682 ** then return TRUE.  If pIdList==NULL, then it is considered a
 683 ** wildcard that matches anything.  Likewise if pEList==NULL then
 684 ** it matches anything so always return true.  Return false only
 685 ** if there is no match.
 686 */
 687 static int checkColumnOverlap(IdList *pIdList, ExprList *pEList){
 688   int e;
 689   if( pIdList==0 || NEVER(pEList==0) ) return 1;
 690   for(e=0; e<pEList->nExpr; e++){
 691     if( sqlite3IdListIndex(pIdList, pEList->a[e].zEName)>=0 ) return 1;
 692   }
 693   return 0;
 694 }
 695
 696 /*
 697 ** Return a list of all triggers on table pTab if there exists at least
 698 ** one trigger that must be fired when an operation of type 'op' is
 699 ** performed on the table, and, if that operation is an UPDATE, if at
 700 ** least one of the columns in pChanges is being modified.
 701 */
 702 Trigger *sqlite3TriggersExist(
 703   Parse *pParse,          /* Parse context */
 704   Table *pTab,            /* The table the contains the triggers */
 705   int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */
 706   ExprList *pChanges,     /* Columns that change in an UPDATE statement */
 707   int *pMask              /* OUT: Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
 708 ){
 709   int mask = 0;
 710   Trigger *pList = 0;
 711   Trigger *p;
 712
 713   if( (pParse->db->flags & SQLITE_EnableTrigger)!=0 ){
 714     pList = sqlite3TriggerList(pParse, pTab);
 715   }
 716   assert( pList==0 || IsVirtual(pTab)==0 );
 717   for(p=pList; p; p=p->pNext){
 718     if( p->op==op && checkColumnOverlap(p->pColumns, pChanges) ){
 719       mask |= p->tr_tm;
 720     }
 721   }
 722   if( pMask ){
 723     *pMask = mask;
 724   }
 725   return (mask ? pList : 0);
 726 }
 727
 728 /*
 729 ** Convert the pStep->zTarget string into a SrcList and return a pointer
 730 ** to that SrcList.
 731 **
 732 ** This routine adds a specific database name, if needed, to the target when
 733 ** forming the SrcList.  This prevents a trigger in one database from
 734 ** referring to a target in another database.  An exception is when the
 735 ** trigger is in TEMP in which case it can refer to any other database it
 736 ** wants.
 737 */
 738 static SrcList *targetSrcList(
 739   Parse *pParse,       /* The parsing context */
 740   TriggerStep *pStep   /* The trigger containing the target token */
 741 ){
 742   sqlite3 *db = pParse->db;
 743   int iDb;             /* Index of the database to use */
 744   SrcList *pSrc;       /* SrcList to be returned */
 745
 746   pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
 747   if( pSrc ){
 748     assert( pSrc->nSrc>0 );
 749     pSrc->a[pSrc->nSrc-1].zName = sqlite3DbStrDup(db, pStep->zTarget);
 750     iDb = sqlite3SchemaToIndex(db, pStep->pTrig->pSchema);
 751     if( iDb==0 || iDb>=2 ){
 752       const char *zDb;
 753       assert( iDb<db->nDb );
 754       zDb = db->aDb[iDb].zDbSName;
 755       pSrc->a[pSrc->nSrc-1].zDatabase =  sqlite3DbStrDup(db, zDb);
 756     }
 757   }
 758   return pSrc;
 759 }
 760
 761 /*
 762 ** Generate VDBE code for the statements inside the body of a single
 763 ** trigger.
 764 */
 765 static int codeTriggerProgram(
 766   Parse *pParse,            /* The parser context */
 767   TriggerStep *pStepList,   /* List of statements inside the trigger body */
 768   int orconf                /* Conflict algorithm. (OE_Abort, etc) */
 769 ){
 770   TriggerStep *pStep;
 771   Vdbe *v = pParse->pVdbe;
 772   sqlite3 *db = pParse->db;
 773
 774   assert( pParse->pTriggerTab && pParse->pToplevel );
 775   assert( pStepList );
 776   assert( v!=0 );
 777   for(pStep=pStepList; pStep; pStep=pStep->pNext){
 778     /* Figure out the ON CONFLICT policy that will be used for this step
 779     ** of the trigger program. If the statement that caused this trigger
 780     ** to fire had an explicit ON CONFLICT, then use it. Otherwise, use
 781     ** the ON CONFLICT policy that was specified as part of the trigger
 782     ** step statement. Example:
 783     **
 784     **   CREATE TRIGGER AFTER INSERT ON t1 BEGIN;
 785     **     INSERT OR REPLACE INTO t2 VALUES(new.a, new.b);
 786     **   END;
 787     **
 788     **   INSERT INTO t1 ... ;            -- insert into t2 uses REPLACE policy
 789     **   INSERT OR IGNORE INTO t1 ... ;  -- insert into t2 uses IGNORE policy
 790     */
 791     pParse->eOrconf = (orconf==OE_Default)?pStep->orconf:(u8)orconf;
 792     assert( pParse->okConstFactor==0 );
 793
 794 #ifndef SQLITE_OMIT_TRACE
 795     if( pStep->zSpan ){
 796       sqlite3VdbeAddOp4(v, OP_Trace, 0x7fffffff, 1, 0,
 797                         sqlite3MPrintf(db, "-- %s", pStep->zSpan),
 798                         P4_DYNAMIC);
 799     }
 800 #endif
 801
 802     switch( pStep->op ){
 803       case TK_UPDATE: {
 804         sqlite3Update(pParse,
 805           targetSrcList(pParse, pStep),
 806           sqlite3ExprListDup(db, pStep->pExprList, 0),
 807           sqlite3ExprDup(db, pStep->pWhere, 0),
 808           pParse->eOrconf, 0, 0, 0
 809         );
 810         break;
 811       }
 812       case TK_INSERT: {
 813         sqlite3Insert(pParse,
 814           targetSrcList(pParse, pStep),
 815           sqlite3SelectDup(db, pStep->pSelect, 0),
 816           sqlite3IdListDup(db, pStep->pIdList),
 817           pParse->eOrconf,
 818           sqlite3UpsertDup(db, pStep->pUpsert)
 819         );
 820         break;
 821       }
 822       case TK_DELETE: {
 823         sqlite3DeleteFrom(pParse,
 824           targetSrcList(pParse, pStep),
 825           sqlite3ExprDup(db, pStep->pWhere, 0), 0, 0
 826         );
 827         break;
 828       }
 829       default: assert( pStep->op==TK_SELECT ); {
 830         SelectDest sDest;
 831         Select *pSelect = sqlite3SelectDup(db, pStep->pSelect, 0);
 832         sqlite3SelectDestInit(&sDest, SRT_Discard, 0);
 833         sqlite3Select(pParse, pSelect, &sDest);
 834         sqlite3SelectDelete(db, pSelect);
 835         break;
 836       }
 837     }
 838     if( pStep->op!=TK_SELECT ){
 839       sqlite3VdbeAddOp0(v, OP_ResetCount);
 840     }
 841   }
 842
 843   return 0;
 844 }
 845
 846 #ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
 847 /*
 848 ** This function is used to add VdbeComment() annotations to a VDBE
 849 ** program. It is not used in production code, only for debugging.
 850 */
 851 static const char *onErrorText(int onError){
 852   switch( onError ){
 853     case OE_Abort:    return "abort";
 854     case OE_Rollback: return "rollback";
 855     case OE_Fail:     return "fail";
 856     case OE_Replace:  return "replace";
 857     case OE_Ignore:   return "ignore";
 858     case OE_Default:  return "default";
 859   }
 860   return "n/a";
 861 }
 862 #endif
 863
 864 /*
 865 ** Parse context structure pFrom has just been used to create a sub-vdbe
 866 ** (trigger program). If an error has occurred, transfer error information
 867 ** from pFrom to pTo.
 868 */
 869 static void transferParseError(Parse *pTo, Parse *pFrom){
 870   assert( pFrom->zErrMsg==0 || pFrom->nErr );
 871   assert( pTo->zErrMsg==0 || pTo->nErr );
 872   if( pTo->nErr==0 ){
 873     pTo->zErrMsg = pFrom->zErrMsg;
 874     pTo->nErr = pFrom->nErr;
 875     pTo->rc = pFrom->rc;
 876   }else{
 877     sqlite3DbFree(pFrom->db, pFrom->zErrMsg);
 878   }
 879 }
 880
 881 /*
 882 ** Create and populate a new TriggerPrg object with a sub-program
 883 ** implementing trigger pTrigger with ON CONFLICT policy orconf.
 884 */
 885 static TriggerPrg *codeRowTrigger(
 886   Parse *pParse,       /* Current parse context */
 887   Trigger *pTrigger,   /* Trigger to code */
 888   Table *pTab,         /* The table pTrigger is attached to */
 889   int orconf           /* ON CONFLICT policy to code trigger program with */
 890 ){
 891   Parse *pTop = sqlite3ParseToplevel(pParse);
 892   sqlite3 *db = pParse->db;   /* Database handle */
 893   TriggerPrg *pPrg;           /* Value to return */
 894   Expr *pWhen = 0;            /* Duplicate of trigger WHEN expression */
 895   Vdbe *v;                    /* Temporary VM */
 896   NameContext sNC;            /* Name context for sub-vdbe */
 897   SubProgram *pProgram = 0;   /* Sub-vdbe for trigger program */
 898   Parse *pSubParse;           /* Parse context for sub-vdbe */
 899   int iEndTrigger = 0;        /* Label to jump to if WHEN is false */
 900
 901   assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
 902   assert( pTop->pVdbe );
 903
 904   /* Allocate the TriggerPrg and SubProgram objects. To ensure that they
 905   ** are freed if an error occurs, link them into the Parse.pTriggerPrg
 906   ** list of the top-level Parse object sooner rather than later.  */
 907   pPrg = sqlite3DbMallocZero(db, sizeof(TriggerPrg));
 908   if( !pPrg ) return 0;
 909   pPrg->pNext = pTop->pTriggerPrg;
 910   pTop->pTriggerPrg = pPrg;
 911   pPrg->pProgram = pProgram = sqlite3DbMallocZero(db, sizeof(SubProgram));
 912   if( !pProgram ) return 0;
 913   sqlite3VdbeLinkSubProgram(pTop->pVdbe, pProgram);
 914   pPrg->pTrigger = pTrigger;
 915   pPrg->orconf = orconf;
 916   pPrg->aColmask[0] = 0xffffffff;
 917   pPrg->aColmask[1] = 0xffffffff;
 918
 919   /* Allocate and populate a new Parse context to use for coding the
 920   ** trigger sub-program.  */
 921   pSubParse = sqlite3StackAllocZero(db, sizeof(Parse));
 922   if( !pSubParse ) return 0;
 923   memset(&sNC, 0, sizeof(sNC));
 924   sNC.pParse = pSubParse;
 925   pSubParse->db = db;
 926   pSubParse->pTriggerTab = pTab;
 927   pSubParse->pToplevel = pTop;
 928   pSubParse->zAuthContext = pTrigger->zName;
 929   pSubParse->eTriggerOp = pTrigger->op;
 930   pSubParse->nQueryLoop = pParse->nQueryLoop;
 931   pSubParse->disableVtab = pParse->disableVtab;
 932
 933   v = sqlite3GetVdbe(pSubParse);
 934   if( v ){
 935     VdbeComment((v, "Start: %s.%s (%s %s%s%s ON %s)",
 936       pTrigger->zName, onErrorText(orconf),
 937       (pTrigger->tr_tm==TRIGGER_BEFORE ? "BEFORE" : "AFTER"),
 938         (pTrigger->op==TK_UPDATE ? "UPDATE" : ""),
 939         (pTrigger->op==TK_INSERT ? "INSERT" : ""),
 940         (pTrigger->op==TK_DELETE ? "DELETE" : ""),
 941       pTab->zName
 942     ));
 943 #ifndef SQLITE_OMIT_TRACE
 944     if( pTrigger->zName ){
 945       sqlite3VdbeChangeP4(v, -1,
 946         sqlite3MPrintf(db, "-- TRIGGER %s", pTrigger->zName), P4_DYNAMIC
 947       );
 948     }
 949 #endif
 950
 951     /* If one was specified, code the WHEN clause. If it evaluates to false
 952     ** (or NULL) the sub-vdbe is immediately halted by jumping to the
 953     ** OP_Halt inserted at the end of the program.  */
 954     if( pTrigger->pWhen ){
 955       pWhen = sqlite3ExprDup(db, pTrigger->pWhen, 0);
 956       if( SQLITE_OK==sqlite3ResolveExprNames(&sNC, pWhen)
 957        && db->mallocFailed==0
 958       ){
 959         iEndTrigger = sqlite3VdbeMakeLabel(pSubParse);
 960         sqlite3ExprIfFalse(pSubParse, pWhen, iEndTrigger, SQLITE_JUMPIFNULL);
 961       }
 962       sqlite3ExprDelete(db, pWhen);
 963     }
 964
 965     /* Code the trigger program into the sub-vdbe. */
 966     codeTriggerProgram(pSubParse, pTrigger->step_list, orconf);
 967
 968     /* Insert an OP_Halt at the end of the sub-program. */
 969     if( iEndTrigger ){
 970       sqlite3VdbeResolveLabel(v, iEndTrigger);
 971     }
 972     sqlite3VdbeAddOp0(v, OP_Halt);
 973     VdbeComment((v, "End: %s.%s", pTrigger->zName, onErrorText(orconf)));
 974
 975     transferParseError(pParse, pSubParse);
 976     if( db->mallocFailed==0 && pParse->nErr==0 ){
 977       pProgram->aOp = sqlite3VdbeTakeOpArray(v, &pProgram->nOp, &pTop->nMaxArg);
 978     }
 979     pProgram->nMem = pSubParse->nMem;
 980     pProgram->nCsr = pSubParse->nTab;
 981     pProgram->token = (void *)pTrigger;
 982     pPrg->aColmask[0] = pSubParse->oldmask;
 983     pPrg->aColmask[1] = pSubParse->newmask;
 984     sqlite3VdbeDelete(v);
 985   }
 986
 987   assert( !pSubParse->pAinc       && !pSubParse->pZombieTab );
 988   assert( !pSubParse->pTriggerPrg && !pSubParse->nMaxArg );
 989   sqlite3ParserReset(pSubParse);
 990   sqlite3StackFree(db, pSubParse);
 991
 992   return pPrg;
 993 }
 994
 995 /*
 996 ** Return a pointer to a TriggerPrg object containing the sub-program for
 997 ** trigger pTrigger with default ON CONFLICT algorithm orconf. If no such
 998 ** TriggerPrg object exists, a new object is allocated and populated before
 999 ** being returned.
1000 */
1001 static TriggerPrg *getRowTrigger(
1002   Parse *pParse,       /* Current parse context */
1003   Trigger *pTrigger,   /* Trigger to code */
1004   Table *pTab,         /* The table trigger pTrigger is attached to */
1005   int orconf           /* ON CONFLICT algorithm. */
1006 ){
1007   Parse *pRoot = sqlite3ParseToplevel(pParse);
1008   TriggerPrg *pPrg;
1009
1010   assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
1011
1012   /* It may be that this trigger has already been coded (or is in the
1013   ** process of being coded). If this is the case, then an entry with
1014   ** a matching TriggerPrg.pTrigger field will be present somewhere
1015   ** in the Parse.pTriggerPrg list. Search for such an entry.  */
1016   for(pPrg=pRoot->pTriggerPrg;
1017       pPrg && (pPrg->pTrigger!=pTrigger || pPrg->orconf!=orconf);
1018       pPrg=pPrg->pNext
1019   );
1020
1021   /* If an existing TriggerPrg could not be located, create a new one. */
1022   if( !pPrg ){
1023     pPrg = codeRowTrigger(pParse, pTrigger, pTab, orconf);
1024   }
1025
1026   return pPrg;
1027 }
1028
1029 /*
1030 ** Generate code for the trigger program associated with trigger p on
1031 ** table pTab. The reg, orconf and ignoreJump parameters passed to this
1032 ** function are the same as those described in the header function for
1033 ** sqlite3CodeRowTrigger()
1034 */
1035 void sqlite3CodeRowTriggerDirect(
1036   Parse *pParse,       /* Parse context */
1037   Trigger *p,          /* Trigger to code */
1038   Table *pTab,         /* The table to code triggers from */
1039   int reg,             /* Reg array containing OLD.* and NEW.* values */
1040   int orconf,          /* ON CONFLICT policy */
1041   int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
1042 ){
1043   Vdbe *v = sqlite3GetVdbe(pParse); /* Main VM */
1044   TriggerPrg *pPrg;
1045   pPrg = getRowTrigger(pParse, p, pTab, orconf);
1046   assert( pPrg || pParse->nErr || pParse->db->mallocFailed );
1047
1048   /* Code the OP_Program opcode in the parent VDBE. P4 of the OP_Program
1049   ** is a pointer to the sub-vdbe containing the trigger program.  */
1050   if( pPrg ){
1051     int bRecursive = (p->zName && 0==(pParse->db->flags&SQLITE_RecTriggers));
1052
1053     sqlite3VdbeAddOp4(v, OP_Program, reg, ignoreJump, ++pParse->nMem,
1054                       (const char *)pPrg->pProgram, P4_SUBPROGRAM);
1055     VdbeComment(
1056         (v, "Call: %s.%s", (p->zName?p->zName:"fkey"), onErrorText(orconf)));
1057
1058     /* Set the P5 operand of the OP_Program instruction to non-zero if
1059     ** recursive invocation of this trigger program is disallowed. Recursive
1060     ** invocation is disallowed if (a) the sub-program is really a trigger,
1061     ** not a foreign key action, and (b) the flag to enable recursive triggers
1062     ** is clear.  */
1063     sqlite3VdbeChangeP5(v, (u8)bRecursive);
1064   }
1065 }
1066
1067 /*
1068 ** This is called to code the required FOR EACH ROW triggers for an operation
1069 ** on table pTab. The operation to code triggers for (INSERT, UPDATE or DELETE)
1070 ** is given by the op parameter. The tr_tm parameter determines whether the
1071 ** BEFORE or AFTER triggers are coded. If the operation is an UPDATE, then
1072 ** parameter pChanges is passed the list of columns being modified.
1073 **
1074 ** If there are no triggers that fire at the specified time for the specified
1075 ** operation on pTab, this function is a no-op.
1076 **
1077 ** The reg argument is the address of the first in an array of registers
1078 ** that contain the values substituted for the new.* and old.* references
1079 ** in the trigger program. If N is the number of columns in table pTab
1080 ** (a copy of pTab->nCol), then registers are populated as follows:
1081 **
1082 **   Register       Contains
1083 **   ------------------------------------------------------
1084 **   reg+0          OLD.rowid
1085 **   reg+1          OLD.* value of left-most column of pTab
1086 **   ...            ...
1087 **   reg+N          OLD.* value of right-most column of pTab
1088 **   reg+N+1        NEW.rowid
1089 **   reg+N+2        OLD.* value of left-most column of pTab
1090 **   ...            ...
1091 **   reg+N+N+1      NEW.* value of right-most column of pTab
1092 **
1093 ** For ON DELETE triggers, the registers containing the NEW.* values will
1094 ** never be accessed by the trigger program, so they are not allocated or
1095 ** populated by the caller (there is no data to populate them with anyway).
1096 ** Similarly, for ON INSERT triggers the values stored in the OLD.* registers
1097 ** are never accessed, and so are not allocated by the caller. So, for an
1098 ** ON INSERT trigger, the value passed to this function as parameter reg
1099 ** is not a readable register, although registers (reg+N) through
1100 ** (reg+N+N+1) are.
1101 **
1102 ** Parameter orconf is the default conflict resolution algorithm for the
1103 ** trigger program to use (REPLACE, IGNORE etc.). Parameter ignoreJump
1104 ** is the instruction that control should jump to if a trigger program
1105 ** raises an IGNORE exception.
1106 */
1107 void sqlite3CodeRowTrigger(
1108   Parse *pParse,       /* Parse context */
1109   Trigger *pTrigger,   /* List of triggers on table pTab */
1110   int op,              /* One of TK_UPDATE, TK_INSERT, TK_DELETE */
1111   ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
1112   int tr_tm,           /* One of TRIGGER_BEFORE, TRIGGER_AFTER */
1113   Table *pTab,         /* The table to code triggers from */
1114   int reg,             /* The first in an array of registers (see above) */
1115   int orconf,          /* ON CONFLICT policy */
1116   int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
1117 ){
1118   Trigger *p;          /* Used to iterate through pTrigger list */
1119
1120   assert( op==TK_UPDATE || op==TK_INSERT || op==TK_DELETE );
1121   assert( tr_tm==TRIGGER_BEFORE || tr_tm==TRIGGER_AFTER );
1122   assert( (op==TK_UPDATE)==(pChanges!=0) );
1123
1124   for(p=pTrigger; p; p=p->pNext){
1125
1126     /* Sanity checking:  The schema for the trigger and for the table are
1127     ** always defined.  The trigger must be in the same schema as the table
1128     ** or else it must be a TEMP trigger. */
1129     assert( p->pSchema!=0 );
1130     assert( p->pTabSchema!=0 );
1131     assert( p->pSchema==p->pTabSchema
1132          || p->pSchema==pParse->db->aDb[1].pSchema );
1133
1134     /* Determine whether we should code this trigger */
1135     if( p->op==op
1136      && p->tr_tm==tr_tm
1137      && checkColumnOverlap(p->pColumns, pChanges)
1138     ){
1139       sqlite3CodeRowTriggerDirect(pParse, p, pTab, reg, orconf, ignoreJump);
1140     }
1141   }
1142 }
1143
1144 /*
1145 ** Triggers may access values stored in the old.* or new.* pseudo-table.
1146 ** This function returns a 32-bit bitmask indicating which columns of the
1147 ** old.* or new.* tables actually are used by triggers. This information
1148 ** may be used by the caller, for example, to avoid having to load the entire
1149 ** old.* record into memory when executing an UPDATE or DELETE command.
1150 **
1151 ** Bit 0 of the returned mask is set if the left-most column of the
1152 ** table may be accessed using an [old|new].<col> reference. Bit 1 is set if
1153 ** the second leftmost column value is required, and so on. If there
1154 ** are more than 32 columns in the table, and at least one of the columns
1155 ** with an index greater than 32 may be accessed, 0xffffffff is returned.
1156 **
1157 ** It is not possible to determine if the old.rowid or new.rowid column is
1158 ** accessed by triggers. The caller must always assume that it is.
1159 **
1160 ** Parameter isNew must be either 1 or 0. If it is 0, then the mask returned
1161 ** applies to the old.* table. If 1, the new.* table.
1162 **
1163 ** Parameter tr_tm must be a mask with one or both of the TRIGGER_BEFORE
1164 ** and TRIGGER_AFTER bits set. Values accessed by BEFORE triggers are only
1165 ** included in the returned mask if the TRIGGER_BEFORE bit is set in the
1166 ** tr_tm parameter. Similarly, values accessed by AFTER triggers are only
1167 ** included in the returned mask if the TRIGGER_AFTER bit is set in tr_tm.
1168 */
1169 u32 sqlite3TriggerColmask(
1170   Parse *pParse,       /* Parse context */
1171   Trigger *pTrigger,   /* List of triggers on table pTab */
1172   ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
1173   int isNew,           /* 1 for new.* ref mask, 0 for old.* ref mask */
1174   int tr_tm,           /* Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
1175   Table *pTab,         /* The table to code triggers from */
1176   int orconf           /* Default ON CONFLICT policy for trigger steps */
1177 ){
1178   const int op = pChanges ? TK_UPDATE : TK_DELETE;
1179   u32 mask = 0;
1180   Trigger *p;
1181
1182   assert( isNew==1 || isNew==0 );
1183   for(p=pTrigger; p; p=p->pNext){
1184     if( p->op==op && (tr_tm&p->tr_tm)
1185      && checkColumnOverlap(p->pColumns,pChanges)
1186     ){
1187       TriggerPrg *pPrg;
1188       pPrg = getRowTrigger(pParse, p, pTab, orconf);
1189       if( pPrg ){
1190         mask |= pPrg->aColmask[isNew];
1191       }
1192     }
1193   }
1194
1195   return mask;
1196 }
1197
1198 #endif /* !defined(SQLITE_OMIT_TRIGGER) */