sqlite3/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 *
  12 */
  13 #include "sqliteInt.h"
  14
  15 #ifndef SQLITE_OMIT_TRIGGER
  16 /*
  17 ** Delete a linked list of TriggerStep structures.
  18 */
  19 void sqlite3DeleteTriggerStep(TriggerStep *pTriggerStep){
  20   while( pTriggerStep ){
  21     TriggerStep * pTmp = pTriggerStep;
  22     pTriggerStep = pTriggerStep->pNext;
  23
  24     if( pTmp->target.dyn ) sqliteFree((char*)pTmp->target.z);
  25     sqlite3ExprDelete(pTmp->pWhere);
  26     sqlite3ExprListDelete(pTmp->pExprList);
  27     sqlite3SelectDelete(pTmp->pSelect);
  28     sqlite3IdListDelete(pTmp->pIdList);
  29
  30     sqliteFree(pTmp);
  31   }
  32 }
  33
  34 /*
  35 ** This is called by the parser when it sees a CREATE TRIGGER statement
  36 ** up to the point of the BEGIN before the trigger actions.  A Trigger
  37 ** structure is generated based on the information available and stored
  38 ** in pParse->pNewTrigger.  After the trigger actions have been parsed, the
  39 ** sqlite3FinishTrigger() function is called to complete the trigger
  40 ** construction process.
  41 */
  42 void sqlite3BeginTrigger(
  43   Parse *pParse,      /* The parse context of the CREATE TRIGGER statement */
  44   Token *pName1,      /* The name of the trigger */
  45   Token *pName2,      /* The name of the trigger */
  46   int tr_tm,          /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD */
  47   int op,             /* One of TK_INSERT, TK_UPDATE, TK_DELETE */
  48   IdList *pColumns,   /* column list if this is an UPDATE OF trigger */
  49   SrcList *pTableName,/* The name of the table/view the trigger applies to */
  50   int foreach,        /* One of TK_ROW or TK_STATEMENT */
  51   Expr *pWhen,        /* WHEN clause */
  52   int isTemp          /* True if the TEMPORARY keyword is present */
  53 ){
  54   Trigger *pTrigger = 0;
  55   Table *pTab;
  56   char *zName = 0;        /* Name of the trigger */
  57   sqlite3 *db = pParse->db;
  58   int iDb;                /* The database to store the trigger in */
  59   Token *pName;           /* The unqualified db name */
  60   DbFixer sFix;
  61
  62   if( isTemp ){
  63     /* If TEMP was specified, then the trigger name may not be qualified. */
  64     if( pName2 && pName2->n>0 ){
  65       sqlite3ErrorMsg(pParse, "temporary trigger may not have qualified name");
  66       goto trigger_cleanup;
  67     }
  68     iDb = 1;
  69     pName = pName1;
  70   }else{
  71     /* Figure out the db that the the trigger will be created in */
  72     iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);
  73     if( iDb<0 ){
  74       goto trigger_cleanup;
  75     }
  76   }
  77
  78   /* If the trigger name was unqualified, and the table is a temp table,
  79   ** then set iDb to 1 to create the trigger in the temporary database.
  80   ** If sqlite3SrcListLookup() returns 0, indicating the table does not
  81   ** exist, the error is caught by the block below.
  82   */
  83   if( !pTableName || sqlite3_malloc_failed ) goto trigger_cleanup;
  84   pTab = sqlite3SrcListLookup(pParse, pTableName);
  85   if( pName2->n==0 && pTab && pTab->iDb==1 ){
  86     iDb = 1;
  87   }
  88
  89   /* Ensure the table name matches database name and that the table exists */
  90   if( sqlite3_malloc_failed ) goto trigger_cleanup;
  91   assert( pTableName->nSrc==1 );
  92   if( sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName) &&
  93       sqlite3FixSrcList(&sFix, pTableName) ){
  94     goto trigger_cleanup;
  95   }
  96   pTab = sqlite3SrcListLookup(pParse, pTableName);
  97   if( !pTab ){
  98     /* The table does not exist. */
  99     goto trigger_cleanup;
 100   }
 101
 102   /* Check that the trigger name is not reserved and that no trigger of the
 103   ** specified name exists */
 104   zName = sqlite3NameFromToken(pName);
 105   if( !zName || SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){
 106     goto trigger_cleanup;
 107   }
 108   if( sqlite3HashFind(&(db->aDb[iDb].trigHash), zName,pName->n+1) ){
 109     sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);
 110     goto trigger_cleanup;
 111   }
 112
 113   /* Do not create a trigger on a system table */
 114   if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){
 115     sqlite3ErrorMsg(pParse, "cannot create trigger on system table");
 116     pParse->nErr++;
 117     goto trigger_cleanup;
 118   }
 119
 120   /* INSTEAD of triggers are only for views and views only support INSTEAD
 121   ** of triggers.
 122   */
 123   if( pTab->pSelect && tr_tm!=TK_INSTEAD ){
 124     sqlite3ErrorMsg(pParse, "cannot create %s trigger on view: %S",
 125         (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName, 0);
 126     goto trigger_cleanup;
 127   }
 128   if( !pTab->pSelect && tr_tm==TK_INSTEAD ){
 129     sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"
 130         " trigger on table: %S", pTableName, 0);
 131     goto trigger_cleanup;
 132   }
 133
 134 #ifndef SQLITE_OMIT_AUTHORIZATION
 135   {
 136     int code = SQLITE_CREATE_TRIGGER;
 137     const char *zDb = db->aDb[pTab->iDb].zName;
 138     const char *zDbTrig = isTemp ? db->aDb[1].zName : zDb;
 139     if( pTab->iDb==1 || isTemp ) code = SQLITE_CREATE_TEMP_TRIGGER;
 140     if( sqlite3AuthCheck(pParse, code, zName, pTab->zName, zDbTrig) ){
 141       goto trigger_cleanup;
 142     }
 143     if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(pTab->iDb),0,zDb)){
 144       goto trigger_cleanup;
 145     }
 146   }
 147 #endif
 148
 149   /* INSTEAD OF triggers can only appear on views and BEFORE triggers
 150   ** cannot appear on views.  So we might as well translate every
 151   ** INSTEAD OF trigger into a BEFORE trigger.  It simplifies code
 152   ** elsewhere.
 153   */
 154   if (tr_tm == TK_INSTEAD){
 155     tr_tm = TK_BEFORE;
 156   }
 157
 158   /* Build the Trigger object */
 159   pTrigger = (Trigger*)sqliteMalloc(sizeof(Trigger));
 160   if( pTrigger==0 ) goto trigger_cleanup;
 161   pTrigger->name = zName;
 162   zName = 0;
 163   pTrigger->table = sqliteStrDup(pTableName->a[0].zName);
 164   pTrigger->iDb = iDb;
 165   pTrigger->iTabDb = pTab->iDb;
 166   pTrigger->op = op;
 167   pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;
 168   pTrigger->pWhen = sqlite3ExprDup(pWhen);
 169   pTrigger->pColumns = sqlite3IdListDup(pColumns);
 170   pTrigger->foreach = foreach;
 171   sqlite3TokenCopy(&pTrigger->nameToken,pName);
 172   assert( pParse->pNewTrigger==0 );
 173   pParse->pNewTrigger = pTrigger;
 174
 175 trigger_cleanup:
 176   sqliteFree(zName);
 177   sqlite3SrcListDelete(pTableName);
 178   sqlite3IdListDelete(pColumns);
 179   sqlite3ExprDelete(pWhen);
 180   if( !pParse->pNewTrigger ){
 181     sqlite3DeleteTrigger(pTrigger);
 182   }else{
 183     assert( pParse->pNewTrigger==pTrigger );
 184   }
 185 }
 186
 187 /*
 188 ** This routine is called after all of the trigger actions have been parsed
 189 ** in order to complete the process of building the trigger.
 190 */
 191 void sqlite3FinishTrigger(
 192   Parse *pParse,          /* Parser context */
 193   TriggerStep *pStepList, /* The triggered program */
 194   Token *pAll             /* Token that describes the complete CREATE TRIGGER */
 195 ){
 196   Trigger *pTrig = 0;     /* The trigger whose construction is finishing up */
 197   sqlite3 *db = pParse->db;  /* The database */
 198   DbFixer sFix;
 199
 200   pTrig = pParse->pNewTrigger;
 201   pParse->pNewTrigger = 0;
 202   if( pParse->nErr || pTrig==0 ) goto triggerfinish_cleanup;
 203   pTrig->step_list = pStepList;
 204   while( pStepList ){
 205     pStepList->pTrig = pTrig;
 206     pStepList = pStepList->pNext;
 207   }
 208   if( sqlite3FixInit(&sFix, pParse, pTrig->iDb, "trigger", &pTrig->nameToken)
 209           && sqlite3FixTriggerStep(&sFix, pTrig->step_list) ){
 210     goto triggerfinish_cleanup;
 211   }
 212
 213   /* if we are not initializing, and this trigger is not on a TEMP table,
 214   ** build the sqlite_master entry
 215   */
 216   if( !db->init.busy ){
 217     static const VdbeOpList insertTrig[] = {
 218       { OP_NewRowid,   0, 0,  0          },
 219       { OP_String8,    0, 0,  "trigger"  },
 220       { OP_String8,    0, 0,  0          },  /* 2: trigger name */
 221       { OP_String8,    0, 0,  0          },  /* 3: table name */
 222       { OP_Integer,    0, 0,  0          },
 223       { OP_String8,    0, 0,  "CREATE TRIGGER "},
 224       { OP_String8,    0, 0,  0          },  /* 6: SQL */
 225       { OP_Concat,     0, 0,  0          },
 226       { OP_MakeRecord, 5, 0,  "tttit"    },
 227       { OP_Insert,     0, 0,  0          },
 228     };
 229     int addr;
 230     Vdbe *v;
 231
 232     /* Make an entry in the sqlite_master table */
 233     v = sqlite3GetVdbe(pParse);
 234     if( v==0 ) goto triggerfinish_cleanup;
 235     sqlite3BeginWriteOperation(pParse, 0, pTrig->iDb);
 236     sqlite3OpenMasterTable(v, pTrig->iDb);
 237     addr = sqlite3VdbeAddOpList(v, ArraySize(insertTrig), insertTrig);
 238     sqlite3VdbeChangeP3(v, addr+2, pTrig->name, 0);
 239     sqlite3VdbeChangeP3(v, addr+3, pTrig->table, 0);
 240     sqlite3VdbeChangeP3(v, addr+6, pAll->z, pAll->n);
 241     sqlite3ChangeCookie(db, v, pTrig->iDb);
 242     sqlite3VdbeAddOp(v, OP_Close, 0, 0);
 243     sqlite3VdbeOp3(v, OP_ParseSchema, pTrig->iDb, 0,
 244        sqlite3MPrintf("type='trigger' AND name='%q'", pTrig->name), P3_DYNAMIC);
 245   }
 246
 247   if( db->init.busy ){
 248     Table *pTab;
 249     Trigger *pDel;
 250     pDel = sqlite3HashInsert(&db->aDb[pTrig->iDb].trigHash,
 251                      pTrig->name, strlen(pTrig->name)+1, pTrig);
 252     if( pDel ){
 253       assert( sqlite3_malloc_failed && pDel==pTrig );
 254       goto triggerfinish_cleanup;
 255     }
 256     pTab = sqlite3LocateTable(pParse,pTrig->table,db->aDb[pTrig->iTabDb].zName);
 257     assert( pTab!=0 );
 258     pTrig->pNext = pTab->pTrigger;
 259     pTab->pTrigger = pTrig;
 260     pTrig = 0;
 261   }
 262
 263 triggerfinish_cleanup:
 264   sqlite3DeleteTrigger(pTrig);
 265   assert( !pParse->pNewTrigger );
 266   sqlite3DeleteTriggerStep(pStepList);
 267 }
 268
 269 /*
 270 ** Make a copy of all components of the given trigger step.  This has
 271 ** the effect of copying all Expr.token.z values into memory obtained
 272 ** from sqliteMalloc().  As initially created, the Expr.token.z values
 273 ** all point to the input string that was fed to the parser.  But that
 274 ** string is ephemeral - it will go away as soon as the sqlite3_exec()
 275 ** call that started the parser exits.  This routine makes a persistent
 276 ** copy of all the Expr.token.z strings so that the TriggerStep structure
 277 ** will be valid even after the sqlite3_exec() call returns.
 278 */
 279 static void sqlitePersistTriggerStep(TriggerStep *p){
 280   if( p->target.z ){
 281     p->target.z = sqliteStrNDup(p->target.z, p->target.n);
 282     p->target.dyn = 1;
 283   }
 284   if( p->pSelect ){
 285     Select *pNew = sqlite3SelectDup(p->pSelect);
 286     sqlite3SelectDelete(p->pSelect);
 287     p->pSelect = pNew;
 288   }
 289   if( p->pWhere ){
 290     Expr *pNew = sqlite3ExprDup(p->pWhere);
 291     sqlite3ExprDelete(p->pWhere);
 292     p->pWhere = pNew;
 293   }
 294   if( p->pExprList ){
 295     ExprList *pNew = sqlite3ExprListDup(p->pExprList);
 296     sqlite3ExprListDelete(p->pExprList);
 297     p->pExprList = pNew;
 298   }
 299   if( p->pIdList ){
 300     IdList *pNew = sqlite3IdListDup(p->pIdList);
 301     sqlite3IdListDelete(p->pIdList);
 302     p->pIdList = pNew;
 303   }
 304 }
 305
 306 /*
 307 ** Turn a SELECT statement (that the pSelect parameter points to) into
 308 ** a trigger step.  Return a pointer to a TriggerStep structure.
 309 **
 310 ** The parser calls this routine when it finds a SELECT statement in
 311 ** body of a TRIGGER.
 312 */
 313 TriggerStep *sqlite3TriggerSelectStep(Select *pSelect){
 314   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
 315   if( pTriggerStep==0 ) return 0;
 316
 317   pTriggerStep->op = TK_SELECT;
 318   pTriggerStep->pSelect = pSelect;
 319   pTriggerStep->orconf = OE_Default;
 320   sqlitePersistTriggerStep(pTriggerStep);
 321
 322   return pTriggerStep;
 323 }
 324
 325 /*
 326 ** Build a trigger step out of an INSERT statement.  Return a pointer
 327 ** to the new trigger step.
 328 **
 329 ** The parser calls this routine when it sees an INSERT inside the
 330 ** body of a trigger.
 331 */
 332 TriggerStep *sqlite3TriggerInsertStep(
 333   Token *pTableName,  /* Name of the table into which we insert */
 334   IdList *pColumn,    /* List of columns in pTableName to insert into */
 335   ExprList *pEList,   /* The VALUE clause: a list of values to be inserted */
 336   Select *pSelect,    /* A SELECT statement that supplies values */
 337   int orconf          /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */
 338 ){
 339   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
 340
 341   assert(pEList == 0 || pSelect == 0);
 342   assert(pEList != 0 || pSelect != 0);
 343
 344   if( pTriggerStep ){
 345     pTriggerStep->op = TK_INSERT;
 346     pTriggerStep->pSelect = pSelect;
 347     pTriggerStep->target  = *pTableName;
 348     pTriggerStep->pIdList = pColumn;
 349     pTriggerStep->pExprList = pEList;
 350     pTriggerStep->orconf = orconf;
 351     sqlitePersistTriggerStep(pTriggerStep);
 352   }else{
 353     sqlite3IdListDelete(pColumn);
 354     sqlite3ExprListDelete(pEList);
 355     sqlite3SelectDup(pSelect);
 356   }
 357
 358   return pTriggerStep;
 359 }
 360
 361 /*
 362 ** Construct a trigger step that implements an UPDATE statement and return
 363 ** a pointer to that trigger step.  The parser calls this routine when it
 364 ** sees an UPDATE statement inside the body of a CREATE TRIGGER.
 365 */
 366 TriggerStep *sqlite3TriggerUpdateStep(
 367   Token *pTableName,   /* Name of the table to be updated */
 368   ExprList *pEList,    /* The SET clause: list of column and new values */
 369   Expr *pWhere,        /* The WHERE clause */
 370   int orconf           /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
 371 ){
 372   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
 373   if( pTriggerStep==0 ) return 0;
 374
 375   pTriggerStep->op = TK_UPDATE;
 376   pTriggerStep->target  = *pTableName;
 377   pTriggerStep->pExprList = pEList;
 378   pTriggerStep->pWhere = pWhere;
 379   pTriggerStep->orconf = orconf;
 380   sqlitePersistTriggerStep(pTriggerStep);
 381
 382   return pTriggerStep;
 383 }
 384
 385 /*
 386 ** Construct a trigger step that implements a DELETE statement and return
 387 ** a pointer to that trigger step.  The parser calls this routine when it
 388 ** sees a DELETE statement inside the body of a CREATE TRIGGER.
 389 */
 390 TriggerStep *sqlite3TriggerDeleteStep(Token *pTableName, Expr *pWhere){
 391   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));
 392   if( pTriggerStep==0 ) return 0;
 393
 394   pTriggerStep->op = TK_DELETE;
 395   pTriggerStep->target  = *pTableName;
 396   pTriggerStep->pWhere = pWhere;
 397   pTriggerStep->orconf = OE_Default;
 398   sqlitePersistTriggerStep(pTriggerStep);
 399
 400   return pTriggerStep;
 401 }
 402
 403 /*
 404 ** Recursively delete a Trigger structure
 405 */
 406 void sqlite3DeleteTrigger(Trigger *pTrigger){
 407   if( pTrigger==0 ) return;
 408   sqlite3DeleteTriggerStep(pTrigger->step_list);
 409   sqliteFree(pTrigger->name);
 410   sqliteFree(pTrigger->table);
 411   sqlite3ExprDelete(pTrigger->pWhen);
 412   sqlite3IdListDelete(pTrigger->pColumns);
 413   if( pTrigger->nameToken.dyn ) sqliteFree((char*)pTrigger->nameToken.z);
 414   sqliteFree(pTrigger);
 415 }
 416
 417 /*
 418 ** This function is called to drop a trigger from the database schema.
 419 **
 420 ** This may be called directly from the parser and therefore identifies
 421 ** the trigger by name.  The sqlite3DropTriggerPtr() routine does the
 422 ** same job as this routine except it takes a pointer to the trigger
 423 ** instead of the trigger name.
 424 **/
 425 void sqlite3DropTrigger(Parse *pParse, SrcList *pName){
 426   Trigger *pTrigger = 0;
 427   int i;
 428   const char *zDb;
 429   const char *zName;
 430   int nName;
 431   sqlite3 *db = pParse->db;
 432
 433   if( sqlite3_malloc_failed ) goto drop_trigger_cleanup;
 434   if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
 435     goto drop_trigger_cleanup;
 436   }
 437
 438   assert( pName->nSrc==1 );
 439   zDb = pName->a[0].zDatabase;
 440   zName = pName->a[0].zName;
 441   nName = strlen(zName);
 442   for(i=OMIT_TEMPDB; i<db->nDb; i++){
 443     int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */
 444     if( zDb && sqlite3StrICmp(db->aDb[j].zName, zDb) ) continue;
 445     pTrigger = sqlite3HashFind(&(db->aDb[j].trigHash), zName, nName+1);
 446     if( pTrigger ) break;
 447   }
 448   if( !pTrigger ){
 449     sqlite3ErrorMsg(pParse, "no such trigger: %S", pName, 0);
 450     goto drop_trigger_cleanup;
 451   }
 452   sqlite3DropTriggerPtr(pParse, pTrigger, 0);
 453
 454 drop_trigger_cleanup:
 455   sqlite3SrcListDelete(pName);
 456 }
 457
 458 /*
 459 ** Return a pointer to the Table structure for the table that a trigger
 460 ** is set on.
 461 */
 462 static Table *tableOfTrigger(sqlite3 *db, Trigger *pTrigger){
 463   return sqlite3FindTable(db,pTrigger->table,db->aDb[pTrigger->iTabDb].zName);
 464 }
 465
 466
 467 /*
 468 ** Drop a trigger given a pointer to that trigger.  If nested is false,
 469 ** then also generate code to remove the trigger from the SQLITE_MASTER
 470 ** table.
 471 */
 472 void sqlite3DropTriggerPtr(Parse *pParse, Trigger *pTrigger, int nested){
 473   Table   *pTable;
 474   Vdbe *v;
 475   sqlite3 *db = pParse->db;
 476   int iDb;
 477
 478   iDb = pTrigger->iDb;
 479   assert( iDb>=0 && iDb<db->nDb );
 480   pTable = tableOfTrigger(db, pTrigger);
 481   assert(pTable);
 482   assert( pTable->iDb==iDb || iDb==1 );
 483 #ifndef SQLITE_OMIT_AUTHORIZATION
 484   {
 485     int code = SQLITE_DROP_TRIGGER;
 486     const char *zDb = db->aDb[iDb].zName;
 487     const char *zTab = SCHEMA_TABLE(iDb);
 488     if( iDb==1 ) code = SQLITE_DROP_TEMP_TRIGGER;
 489     if( sqlite3AuthCheck(pParse, code, pTrigger->name, pTable->zName, zDb) ||
 490       sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){
 491       return;
 492     }
 493   }
 494 #endif
 495
 496   /* Generate code to destroy the database record of the trigger.
 497   */
 498   if( pTable!=0 && (v = sqlite3GetVdbe(pParse))!=0 ){
 499     int base;
 500     static const VdbeOpList dropTrigger[] = {
 501       { OP_Rewind,     0, ADDR(9),  0},
 502       { OP_String8,    0, 0,        0}, /* 1 */
 503       { OP_Column,     0, 1,        0},
 504       { OP_Ne,         0, ADDR(8),  0},
 505       { OP_String8,    0, 0,        "trigger"},
 506       { OP_Column,     0, 0,        0},
 507       { OP_Ne,         0, ADDR(8),  0},
 508       { OP_Delete,     0, 0,        0},
 509       { OP_Next,       0, ADDR(1),  0}, /* 8 */
 510     };
 511
 512     sqlite3BeginWriteOperation(pParse, 0, iDb);
 513     sqlite3OpenMasterTable(v, iDb);
 514     base = sqlite3VdbeAddOpList(v,  ArraySize(dropTrigger), dropTrigger);
 515     sqlite3VdbeChangeP3(v, base+1, pTrigger->name, 0);
 516     sqlite3ChangeCookie(db, v, iDb);
 517     sqlite3VdbeAddOp(v, OP_Close, 0, 0);
 518     sqlite3VdbeOp3(v, OP_DropTrigger, iDb, 0, pTrigger->name, 0);
 519   }
 520 }
 521
 522 /*
 523 ** Remove a trigger from the hash tables of the sqlite* pointer.
 524 */
 525 void sqlite3UnlinkAndDeleteTrigger(sqlite3 *db, int iDb, const char *zName){
 526   Trigger *pTrigger;
 527   int nName = strlen(zName);
 528   pTrigger = sqlite3HashInsert(&(db->aDb[iDb].trigHash), zName, nName+1, 0);
 529   if( pTrigger ){
 530     Table *pTable = tableOfTrigger(db, pTrigger);
 531     assert( pTable!=0 );
 532     if( pTable->pTrigger == pTrigger ){
 533       pTable->pTrigger = pTrigger->pNext;
 534     }else{
 535       Trigger *cc = pTable->pTrigger;
 536       while( cc ){
 537         if( cc->pNext == pTrigger ){
 538           cc->pNext = cc->pNext->pNext;
 539           break;
 540         }
 541         cc = cc->pNext;
 542       }
 543       assert(cc);
 544     }
 545     sqlite3DeleteTrigger(pTrigger);
 546     db->flags |= SQLITE_InternChanges;
 547   }
 548 }
 549
 550 /*
 551 ** pEList is the SET clause of an UPDATE statement.  Each entry
 552 ** in pEList is of the format <id>=<expr>.  If any of the entries
 553 ** in pEList have an <id> which matches an identifier in pIdList,
 554 ** then return TRUE.  If pIdList==NULL, then it is considered a
 555 ** wildcard that matches anything.  Likewise if pEList==NULL then
 556 ** it matches anything so always return true.  Return false only
 557 ** if there is no match.
 558 */
 559 static int checkColumnOverLap(IdList *pIdList, ExprList *pEList){
 560   int e;
 561   if( !pIdList || !pEList ) return 1;
 562   for(e=0; e<pEList->nExpr; e++){
 563     if( sqlite3IdListIndex(pIdList, pEList->a[e].zName)>=0 ) return 1;
 564   }
 565   return 0;
 566 }
 567
 568 /*
 569 ** Return a bit vector to indicate what kind of triggers exist for operation
 570 ** "op" on table pTab.  If pChanges is not NULL then it is a list of columns
 571 ** that are being updated.  Triggers only match if the ON clause of the
 572 ** trigger definition overlaps the set of columns being updated.
 573 **
 574 ** The returned bit vector is some combination of TRIGGER_BEFORE and
 575 ** TRIGGER_AFTER.
 576 */
 577 int sqlite3TriggersExist(
 578   Parse *pParse,          /* Used to check for recursive triggers */
 579   Table *pTab,            /* The table the contains the triggers */
 580   int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */
 581   ExprList *pChanges      /* Columns that change in an UPDATE statement */
 582 ){
 583   Trigger *pTrigger = pTab->pTrigger;
 584   int mask = 0;
 585
 586   while( pTrigger ){
 587     if( pTrigger->op==op && checkColumnOverLap(pTrigger->pColumns, pChanges) ){
 588       TriggerStack *ss;
 589       ss = pParse->trigStack;
 590       while( ss && ss->pTrigger!=pTab->pTrigger ){
 591         ss = ss->pNext;
 592       }
 593       if( ss==0 ){
 594         mask |= pTrigger->tr_tm;
 595       }
 596     }
 597     pTrigger = pTrigger->pNext;
 598   }
 599   return mask;
 600 }
 601
 602 /*
 603 ** Convert the pStep->target token into a SrcList and return a pointer
 604 ** to that SrcList.
 605 **
 606 ** This routine adds a specific database name, if needed, to the target when
 607 ** forming the SrcList.  This prevents a trigger in one database from
 608 ** referring to a target in another database.  An exception is when the
 609 ** trigger is in TEMP in which case it can refer to any other database it
 610 ** wants.
 611 */
 612 static SrcList *targetSrcList(
 613   Parse *pParse,       /* The parsing context */
 614   TriggerStep *pStep   /* The trigger containing the target token */
 615 ){
 616   Token sDb;           /* Dummy database name token */
 617   int iDb;             /* Index of the database to use */
 618   SrcList *pSrc;       /* SrcList to be returned */
 619
 620   iDb = pStep->pTrig->iDb;
 621   if( iDb==0 || iDb>=2 ){
 622     assert( iDb<pParse->db->nDb );
 623     sDb.z = pParse->db->aDb[iDb].zName;
 624     sDb.n = strlen(sDb.z);
 625     pSrc = sqlite3SrcListAppend(0, &sDb, &pStep->target);
 626   } else {
 627     pSrc = sqlite3SrcListAppend(0, &pStep->target, 0);
 628   }
 629   return pSrc;
 630 }
 631
 632 /*
 633 ** Generate VDBE code for zero or more statements inside the body of a
 634 ** trigger.
 635 */
 636 static int codeTriggerProgram(
 637   Parse *pParse,            /* The parser context */
 638   TriggerStep *pStepList,   /* List of statements inside the trigger body */
 639   int orconfin              /* Conflict algorithm. (OE_Abort, etc) */
 640 ){
 641   TriggerStep * pTriggerStep = pStepList;
 642   int orconf;
 643   Vdbe *v = pParse->pVdbe;
 644
 645   assert( pTriggerStep!=0 );
 646   assert( v!=0 );
 647   sqlite3VdbeAddOp(v, OP_ContextPush, 0, 0);
 648   VdbeComment((v, "# begin trigger %s", pStepList->pTrig->name));
 649   while( pTriggerStep ){
 650     orconf = (orconfin == OE_Default)?pTriggerStep->orconf:orconfin;
 651     pParse->trigStack->orconf = orconf;
 652     switch( pTriggerStep->op ){
 653       case TK_SELECT: {
 654         Select * ss = sqlite3SelectDup(pTriggerStep->pSelect);
 655         assert(ss);
 656         assert(ss->pSrc);
 657         sqlite3SelectResolve(pParse, ss, 0);
 658         sqlite3Select(pParse, ss, SRT_Discard, 0, 0, 0, 0, 0);
 659         sqlite3SelectDelete(ss);
 660         break;
 661       }
 662       case TK_UPDATE: {
 663         SrcList *pSrc;
 664         pSrc = targetSrcList(pParse, pTriggerStep);
 665         sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);
 666         sqlite3Update(pParse, pSrc,
 667                 sqlite3ExprListDup(pTriggerStep->pExprList),
 668                 sqlite3ExprDup(pTriggerStep->pWhere), orconf);
 669         sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);
 670         break;
 671       }
 672       case TK_INSERT: {
 673         SrcList *pSrc;
 674         pSrc = targetSrcList(pParse, pTriggerStep);
 675         sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);
 676         sqlite3Insert(pParse, pSrc,
 677           sqlite3ExprListDup(pTriggerStep->pExprList),
 678           sqlite3SelectDup(pTriggerStep->pSelect),
 679           sqlite3IdListDup(pTriggerStep->pIdList), orconf);
 680         sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);
 681         break;
 682       }
 683       case TK_DELETE: {
 684         SrcList *pSrc;
 685         sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);
 686         pSrc = targetSrcList(pParse, pTriggerStep);
 687         sqlite3DeleteFrom(pParse, pSrc, sqlite3ExprDup(pTriggerStep->pWhere));
 688         sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);
 689         break;
 690       }
 691       default:
 692         assert(0);
 693     }
 694     pTriggerStep = pTriggerStep->pNext;
 695   }
 696   sqlite3VdbeAddOp(v, OP_ContextPop, 0, 0);
 697   VdbeComment((v, "# end trigger %s", pStepList->pTrig->name));
 698
 699   return 0;
 700 }
 701
 702 /*
 703 ** This is called to code FOR EACH ROW triggers.
 704 **
 705 ** When the code that this function generates is executed, the following
 706 ** must be true:
 707 **
 708 ** 1. No cursors may be open in the main database.  (But newIdx and oldIdx
 709 **    can be indices of cursors in temporary tables.  See below.)
 710 **
 711 ** 2. If the triggers being coded are ON INSERT or ON UPDATE triggers, then
 712 **    a temporary vdbe cursor (index newIdx) must be open and pointing at
 713 **    a row containing values to be substituted for new.* expressions in the
 714 **    trigger program(s).
 715 **
 716 ** 3. If the triggers being coded are ON DELETE or ON UPDATE triggers, then
 717 **    a temporary vdbe cursor (index oldIdx) must be open and pointing at
 718 **    a row containing values to be substituted for old.* expressions in the
 719 **    trigger program(s).
 720 **
 721 */
 722 int sqlite3CodeRowTrigger(
 723   Parse *pParse,       /* Parse context */
 724   int op,              /* One of TK_UPDATE, TK_INSERT, TK_DELETE */
 725   ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */
 726   int tr_tm,           /* One of TRIGGER_BEFORE, TRIGGER_AFTER */
 727   Table *pTab,         /* The table to code triggers from */
 728   int newIdx,          /* The indice of the "new" row to access */
 729   int oldIdx,          /* The indice of the "old" row to access */
 730   int orconf,          /* ON CONFLICT policy */
 731   int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */
 732 ){
 733   Trigger *pTrigger;
 734   TriggerStack *pStack;
 735   TriggerStack trigStackEntry;
 736
 737   assert(op == TK_UPDATE || op == TK_INSERT || op == TK_DELETE);
 738   assert(tr_tm == TRIGGER_BEFORE || tr_tm == TRIGGER_AFTER );
 739
 740   assert(newIdx != -1 || oldIdx != -1);
 741
 742   pTrigger = pTab->pTrigger;
 743   while( pTrigger ){
 744     int fire_this = 0;
 745
 746     /* determine whether we should code this trigger */
 747     if( pTrigger->op == op && pTrigger->tr_tm == tr_tm ){
 748       fire_this = 1;
 749       for(pStack=pParse->trigStack; pStack; pStack=pStack->pNext){
 750         if( pStack->pTrigger==pTrigger ){
 751           fire_this = 0;
 752         }
 753       }
 754       if( op == TK_UPDATE && pTrigger->pColumns &&
 755           !checkColumnOverLap(pTrigger->pColumns, pChanges) ){
 756         fire_this = 0;
 757       }
 758     }
 759
 760     if( fire_this ){
 761       int endTrigger;
 762       Expr * whenExpr;
 763       AuthContext sContext;
 764       NameContext sNC;
 765
 766       memset(&sNC, 0, sizeof(sNC));
 767       sNC.pParse = pParse;
 768
 769       /* Push an entry on to the trigger stack */
 770       trigStackEntry.pTrigger = pTrigger;
 771       trigStackEntry.newIdx = newIdx;
 772       trigStackEntry.oldIdx = oldIdx;
 773       trigStackEntry.pTab = pTab;
 774       trigStackEntry.pNext = pParse->trigStack;
 775       trigStackEntry.ignoreJump = ignoreJump;
 776       pParse->trigStack = &trigStackEntry;
 777       sqlite3AuthContextPush(pParse, &sContext, pTrigger->name);
 778
 779       /* code the WHEN clause */
 780       endTrigger = sqlite3VdbeMakeLabel(pParse->pVdbe);
 781       whenExpr = sqlite3ExprDup(pTrigger->pWhen);
 782       if( sqlite3ExprResolveNames(&sNC, whenExpr) ){
 783         pParse->trigStack = trigStackEntry.pNext;
 784         sqlite3ExprDelete(whenExpr);
 785         return 1;
 786       }
 787       sqlite3ExprIfFalse(pParse, whenExpr, endTrigger, 1);
 788       sqlite3ExprDelete(whenExpr);
 789
 790       codeTriggerProgram(pParse, pTrigger->step_list, orconf);
 791
 792       /* Pop the entry off the trigger stack */
 793       pParse->trigStack = trigStackEntry.pNext;
 794       sqlite3AuthContextPop(&sContext);
 795
 796       sqlite3VdbeResolveLabel(pParse->pVdbe, endTrigger);
 797     }
 798     pTrigger = pTrigger->pNext;
 799   }
 800   return 0;
 801 }
 802 #endif /* !defined(SQLITE_OMIT_TRIGGER) */