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 ) sqlite3_free((char*)pTmp->target.z);

    25     sqlite3ExprDelete(pTmp->pWhere);

    26     sqlite3ExprListDelete(pTmp->pExprList);

    27     sqlite3SelectDelete(pTmp->pSelect);

    28     sqlite3IdListDelete(pTmp->pIdList);

    29 

    30     sqlite3_free(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   Expr *pWhen,        /* WHEN clause */

    51   int isTemp,         /* True if the TEMPORARY keyword is present */

    52   int noErr           /* Suppress errors if the trigger already exists */

    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   int iTabDb;

    62 

    63   assert( pName1!=0 );   /* pName1->z might be NULL, but not pName1 itself */

    64   assert( pName2!=0 );

    65   if( isTemp ){

    66     /* If TEMP was specified, then the trigger name may not be qualified. */

    67     if( pName2->n>0 ){

    68       sqlite3ErrorMsg(pParse, "temporary trigger may not have qualified name");

    69       goto trigger_cleanup;

    70     }

    71     iDb = 1;

    72     pName = pName1;

    73   }else{

    74     /* Figure out the db that the the trigger will be created in */

    75     iDb = sqlite3TwoPartName(pParse, pName1, pName2, &pName);

    76     if( iDb<0 ){

    77       goto trigger_cleanup;

    78     }

    79   }

    80 

    81   /* If the trigger name was unqualified, and the table is a temp table,

    82   ** then set iDb to 1 to create the trigger in the temporary database.

    83   ** If sqlite3SrcListLookup() returns 0, indicating the table does not

    84   ** exist, the error is caught by the block below.

    85   */

    86   if( !pTableName || db->mallocFailed ){

    87     goto trigger_cleanup;

    88   }

    89   pTab = sqlite3SrcListLookup(pParse, pTableName);

    90   if( pName2->n==0 && pTab && pTab->pSchema==db->aDb[1].pSchema ){

    91     iDb = 1;

    92   }

    93 

    94   /* Ensure the table name matches database name and that the table exists */

    95   if( db->mallocFailed ) goto trigger_cleanup;

    96   assert( pTableName->nSrc==1 );

    97   if( sqlite3FixInit(&sFix, pParse, iDb, "trigger", pName) && 

    98       sqlite3FixSrcList(&sFix, pTableName) ){

    99     goto trigger_cleanup;

   100   }

   101   pTab = sqlite3SrcListLookup(pParse, pTableName);

   102   if( !pTab ){

   103     /* The table does not exist. */

   104     goto trigger_cleanup;

   105   }

   106   if( IsVirtual(pTab) ){

   107     sqlite3ErrorMsg(pParse, "cannot create triggers on virtual tables");

   108     goto trigger_cleanup;

   109   }

   110 

   111   /* Check that the trigger name is not reserved and that no trigger of the

   112   ** specified name exists */

   113   zName = sqlite3NameFromToken(db, pName);

   114   if( !zName || SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){

   115     goto trigger_cleanup;

   116   }

   117   if( sqlite3HashFind(&(db->aDb[iDb].pSchema->trigHash), zName,strlen(zName)) ){

   118     if( !noErr ){

   119       sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);

   120     }

   121     goto trigger_cleanup;

   122   }

   123 

   124   /* Do not create a trigger on a system table */

   125   if( sqlite3StrNICmp(pTab->zName, "sqlite_", 7)==0 ){

   126     sqlite3ErrorMsg(pParse, "cannot create trigger on system table");

   127     pParse->nErr++;

   128     goto trigger_cleanup;

   129   }

   130 

   131   /* INSTEAD of triggers are only for views and views only support INSTEAD

   132   ** of triggers.

   133   */

   134   if( pTab->pSelect && tr_tm!=TK_INSTEAD ){

   135     sqlite3ErrorMsg(pParse, "cannot create %s trigger on view: %S", 

   136         (tr_tm == TK_BEFORE)?"BEFORE":"AFTER", pTableName, 0);

   137     goto trigger_cleanup;

   138   }

   139   if( !pTab->pSelect && tr_tm==TK_INSTEAD ){

   140     sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"

   141         " trigger on table: %S", pTableName, 0);

   142     goto trigger_cleanup;

   143   }

   144   iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);

   145 

   146 #ifndef SQLITE_OMIT_AUTHORIZATION

   147   {

   148     int code = SQLITE_CREATE_TRIGGER;

   149     const char *zDb = db->aDb[iTabDb].zName;

   150     const char *zDbTrig = isTemp ? db->aDb[1].zName : zDb;

   151     if( iTabDb==1 || isTemp ) code = SQLITE_CREATE_TEMP_TRIGGER;

   152     if( sqlite3AuthCheck(pParse, code, zName, pTab->zName, zDbTrig) ){

   153       goto trigger_cleanup;

   154     }

   155     if( sqlite3AuthCheck(pParse, SQLITE_INSERT, SCHEMA_TABLE(iTabDb),0,zDb)){

   156       goto trigger_cleanup;

   157     }

   158   }

   159 #endif

   160 

   161   /* INSTEAD OF triggers can only appear on views and BEFORE triggers

   162   ** cannot appear on views.  So we might as well translate every

   163   ** INSTEAD OF trigger into a BEFORE trigger.  It simplifies code

   164   ** elsewhere.

   165   */

   166   if (tr_tm == TK_INSTEAD){

   167     tr_tm = TK_BEFORE;

   168   }

   169 

   170   /* Build the Trigger object */

   171   pTrigger = (Trigger*)sqlite3DbMallocZero(db, sizeof(Trigger));

   172   if( pTrigger==0 ) goto trigger_cleanup;

   173   pTrigger->name = zName;

   174   zName = 0;

   175   pTrigger->table = sqlite3DbStrDup(db, pTableName->a[0].zName);

   176   pTrigger->pSchema = db->aDb[iDb].pSchema;

   177   pTrigger->pTabSchema = pTab->pSchema;

   178   pTrigger->op = op;

   179   pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;

   180   pTrigger->pWhen = sqlite3ExprDup(db, pWhen);

   181   pTrigger->pColumns = sqlite3IdListDup(db, pColumns);

   182   sqlite3TokenCopy(db, &pTrigger->nameToken,pName);

   183   assert( pParse->pNewTrigger==0 );

   184   pParse->pNewTrigger = pTrigger;

   185 

   186 trigger_cleanup:

   187   sqlite3_free(zName);

   188   sqlite3SrcListDelete(pTableName);

   189   sqlite3IdListDelete(pColumns);

   190   sqlite3ExprDelete(pWhen);

   191   if( !pParse->pNewTrigger ){

   192     sqlite3DeleteTrigger(pTrigger);

   193   }else{

   194     assert( pParse->pNewTrigger==pTrigger );

   195   }

   196 }

   197 

   198 /*

   199 ** This routine is called after all of the trigger actions have been parsed

   200 ** in order to complete the process of building the trigger.

   201 */

   202 void sqlite3FinishTrigger(

   203   Parse *pParse,          /* Parser context */

   204   TriggerStep *pStepList, /* The triggered program */

   205   Token *pAll             /* Token that describes the complete CREATE TRIGGER */

   206 ){

   207   Trigger *pTrig = 0;     /* The trigger whose construction is finishing up */

   208   sqlite3 *db = pParse->db;  /* The database */

   209   DbFixer sFix;

   210   int iDb;                   /* Database containing the trigger */

   211 

   212   pTrig = pParse->pNewTrigger;

   213   pParse->pNewTrigger = 0;

   214   if( pParse->nErr || !pTrig ) goto triggerfinish_cleanup;

   215   iDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);

   216   pTrig->step_list = pStepList;

   217   while( pStepList ){

   218     pStepList->pTrig = pTrig;

   219     pStepList = pStepList->pNext;

   220   }

   221   if( sqlite3FixInit(&sFix, pParse, iDb, "trigger", &pTrig->nameToken) 

   222           && sqlite3FixTriggerStep(&sFix, pTrig->step_list) ){

   223     goto triggerfinish_cleanup;

   224   }

   225 

   226   /* if we are not initializing, and this trigger is not on a TEMP table, 

   227   ** build the sqlite_master entry

   228   */

   229   if( !db->init.busy ){

   230     static const VdbeOpList insertTrig[] = {

   231       { OP_NewRowid,   0, 0,  0          },

   232       { OP_String8,    0, 0,  "trigger"  },

   233       { OP_String8,    0, 0,  0          },  /* 2: trigger name */

   234       { OP_String8,    0, 0,  0          },  /* 3: table name */

   235       { OP_Integer,    0, 0,  0          },

   236       { OP_String8,    0, 0,  "CREATE TRIGGER "},

   237       { OP_String8,    0, 0,  0          },  /* 6: SQL */

   238       { OP_Concat,     0, 0,  0          }, 

   239       { OP_MakeRecord, 5, 0,  "aaada"    },

   240       { OP_Insert,     0, 0,  0          },

   241     };

   242     int addr;

   243     Vdbe *v;

   244 

   245     /* Make an entry in the sqlite_master table */

   246     v = sqlite3GetVdbe(pParse);

   247     if( v==0 ) goto triggerfinish_cleanup;

   248     sqlite3BeginWriteOperation(pParse, 0, iDb);

   249     sqlite3OpenMasterTable(pParse, iDb);

   250     addr = sqlite3VdbeAddOpList(v, ArraySize(insertTrig), insertTrig);

   251     sqlite3VdbeChangeP3(v, addr+2, pTrig->name, 0); 

   252     sqlite3VdbeChangeP3(v, addr+3, pTrig->table, 0); 

   253     sqlite3VdbeChangeP3(v, addr+6, (char*)pAll->z, pAll->n);

   254     sqlite3ChangeCookie(db, v, iDb);

   255     sqlite3VdbeAddOp(v, OP_Close, 0, 0);

   256     sqlite3VdbeOp3(v, OP_ParseSchema, iDb, 0, sqlite3MPrintf(

   257         db, "type='trigger' AND name='%q'", pTrig->name), P3_DYNAMIC

   258     );

   259   }

   260 

   261   if( db->init.busy ){

   262     int n;

   263     Table *pTab;

   264     Trigger *pDel;

   265     pDel = (Trigger*)sqlite3HashInsert(&db->aDb[iDb].pSchema->trigHash, 

   266                      pTrig->name, strlen(pTrig->name), pTrig);

   267     if( pDel ){

   268       assert( pDel==pTrig );

   269       db->mallocFailed = 1;

   270       goto triggerfinish_cleanup;

   271     }

   272     n = strlen(pTrig->table) + 1;

   273     pTab = (Table*)sqlite3HashFind(&pTrig->pTabSchema->tblHash, pTrig->table, n);

   274     assert( pTab!=0 );

   275     pTrig->pNext = pTab->pTrigger;

   276     pTab->pTrigger = pTrig;

   277     pTrig = 0;

   278   }

   279 

   280 triggerfinish_cleanup:

   281   sqlite3DeleteTrigger(pTrig);

   282   assert( !pParse->pNewTrigger );

   283   sqlite3DeleteTriggerStep(pStepList);

   284 }

   285 

   286 /*

   287 ** Make a copy of all components of the given trigger step.  This has

   288 ** the effect of copying all Expr.token.z values into memory obtained

   289 ** from sqlite3_malloc().  As initially created, the Expr.token.z values

   290 ** all point to the input string that was fed to the parser.  But that

   291 ** string is ephemeral - it will go away as soon as the sqlite3_exec()

   292 ** call that started the parser exits.  This routine makes a persistent

   293 ** copy of all the Expr.token.z strings so that the TriggerStep structure

   294 ** will be valid even after the sqlite3_exec() call returns.

   295 */

   296 static void sqlitePersistTriggerStep(sqlite3 *db, TriggerStep *p){

   297   if( p->target.z ){

   298     p->target.z = (u8*)sqlite3DbStrNDup(db, (char*)p->target.z, p->target.n);

   299     p->target.dyn = 1;

   300   }

   301   if( p->pSelect ){

   302     Select *pNew = sqlite3SelectDup(db, p->pSelect);

   303     sqlite3SelectDelete(p->pSelect);

   304     p->pSelect = pNew;

   305   }

   306   if( p->pWhere ){

   307     Expr *pNew = sqlite3ExprDup(db, p->pWhere);

   308     sqlite3ExprDelete(p->pWhere);

   309     p->pWhere = pNew;

   310   }

   311   if( p->pExprList ){

   312     ExprList *pNew = sqlite3ExprListDup(db, p->pExprList);

   313     sqlite3ExprListDelete(p->pExprList);

   314     p->pExprList = pNew;

   315   }

   316   if( p->pIdList ){

   317     IdList *pNew = sqlite3IdListDup(db, p->pIdList);

   318     sqlite3IdListDelete(p->pIdList);

   319     p->pIdList = pNew;

   320   }

   321 }

   322 

   323 /*

   324 ** Turn a SELECT statement (that the pSelect parameter points to) into

   325 ** a trigger step.  Return a pointer to a TriggerStep structure.

   326 **

   327 ** The parser calls this routine when it finds a SELECT statement in

   328 ** body of a TRIGGER.  

   329 */

   330 TriggerStep *sqlite3TriggerSelectStep(sqlite3 *db, Select *pSelect){

   331   TriggerStep *pTriggerStep = (TriggerStep*)sqlite3DbMallocZero(db, sizeof(TriggerStep));

   332   if( pTriggerStep==0 ) {

   333     sqlite3SelectDelete(pSelect);

   334     return 0;

   335   }

   336 

   337   pTriggerStep->op = TK_SELECT;

   338   pTriggerStep->pSelect = pSelect;

   339   pTriggerStep->orconf = OE_Default;

   340   sqlitePersistTriggerStep(db, pTriggerStep);

   341 

   342   return pTriggerStep;

   343 }

   344 

   345 /*

   346 ** Build a trigger step out of an INSERT statement.  Return a pointer

   347 ** to the new trigger step.

   348 **

   349 ** The parser calls this routine when it sees an INSERT inside the

   350 ** body of a trigger.

   351 */

   352 TriggerStep *sqlite3TriggerInsertStep(

   353   sqlite3 *db,        /* The database connection */

   354   Token *pTableName,  /* Name of the table into which we insert */

   355   IdList *pColumn,    /* List of columns in pTableName to insert into */

   356   ExprList *pEList,   /* The VALUE clause: a list of values to be inserted */

   357   Select *pSelect,    /* A SELECT statement that supplies values */

   358   int orconf          /* The conflict algorithm (OE_Abort, OE_Replace, etc.) */

   359 ){

   360   TriggerStep *pTriggerStep;

   361 

   362   assert(pEList == 0 || pSelect == 0);

   363   assert(pEList != 0 || pSelect != 0 || db->mallocFailed);

   364 

   365   pTriggerStep = (TriggerStep*)sqlite3DbMallocZero(db, sizeof(TriggerStep));

   366   if( pTriggerStep ){

   367     pTriggerStep->op = TK_INSERT;

   368     pTriggerStep->pSelect = pSelect;

   369     pTriggerStep->target  = *pTableName;

   370     pTriggerStep->pIdList = pColumn;

   371     pTriggerStep->pExprList = pEList;

   372     pTriggerStep->orconf = orconf;

   373     sqlitePersistTriggerStep(db, pTriggerStep);

   374   }else{

   375     sqlite3IdListDelete(pColumn);

   376     sqlite3ExprListDelete(pEList);

   377     sqlite3SelectDelete(pSelect);

   378   }

   379 

   380   return pTriggerStep;

   381 }

   382 

   383 /*

   384 ** Construct a trigger step that implements an UPDATE statement and return

   385 ** a pointer to that trigger step.  The parser calls this routine when it

   386 ** sees an UPDATE statement inside the body of a CREATE TRIGGER.

   387 */

   388 TriggerStep *sqlite3TriggerUpdateStep(

   389   sqlite3 *db,         /* The database connection */

   390   Token *pTableName,   /* Name of the table to be updated */

   391   ExprList *pEList,    /* The SET clause: list of column and new values */

   392   Expr *pWhere,        /* The WHERE clause */

   393   int orconf           /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */

   394 ){

   395   TriggerStep *pTriggerStep = (TriggerStep*)sqlite3DbMallocZero(db, sizeof(TriggerStep));

   396   if( pTriggerStep==0 ){

   397      sqlite3ExprListDelete(pEList);

   398      sqlite3ExprDelete(pWhere);

   399      return 0;

   400   }

   401 

   402   pTriggerStep->op = TK_UPDATE;

   403   pTriggerStep->target  = *pTableName;

   404   pTriggerStep->pExprList = pEList;

   405   pTriggerStep->pWhere = pWhere;

   406   pTriggerStep->orconf = orconf;

   407   sqlitePersistTriggerStep(db, pTriggerStep);

   408 

   409   return pTriggerStep;

   410 }

   411 

   412 /*

   413 ** Construct a trigger step that implements a DELETE statement and return

   414 ** a pointer to that trigger step.  The parser calls this routine when it

   415 ** sees a DELETE statement inside the body of a CREATE TRIGGER.

   416 */

   417 TriggerStep *sqlite3TriggerDeleteStep(

   418   sqlite3 *db,            /* Database connection */

   419   Token *pTableName,      /* The table from which rows are deleted */

   420   Expr *pWhere            /* The WHERE clause */

   421 ){

   422   TriggerStep *pTriggerStep = (TriggerStep*)sqlite3DbMallocZero(db, sizeof(TriggerStep));

   423   if( pTriggerStep==0 ){

   424     sqlite3ExprDelete(pWhere);

   425     return 0;

   426   }

   427 

   428   pTriggerStep->op = TK_DELETE;

   429   pTriggerStep->target  = *pTableName;

   430   pTriggerStep->pWhere = pWhere;

   431   pTriggerStep->orconf = OE_Default;

   432   sqlitePersistTriggerStep(db, pTriggerStep);

   433 

   434   return pTriggerStep;

   435 }

   436 

   437 /* 

   438 ** Recursively delete a Trigger structure

   439 */

   440 void sqlite3DeleteTrigger(Trigger *pTrigger){

   441   if( pTrigger==0 ) return;

   442   sqlite3DeleteTriggerStep(pTrigger->step_list);

   443   sqlite3_free(pTrigger->name);

   444   sqlite3_free(pTrigger->table);

   445   sqlite3ExprDelete(pTrigger->pWhen);

   446   sqlite3IdListDelete(pTrigger->pColumns);

   447   if( pTrigger->nameToken.dyn ) sqlite3_free((char*)pTrigger->nameToken.z);

   448   sqlite3_free(pTrigger);

   449 }

   450 

   451 /*

   452 ** This function is called to drop a trigger from the database schema. 

   453 **

   454 ** This may be called directly from the parser and therefore identifies

   455 ** the trigger by name.  The sqlite3DropTriggerPtr() routine does the

   456 ** same job as this routine except it takes a pointer to the trigger

   457 ** instead of the trigger name.

   458 **/

   459 void sqlite3DropTrigger(Parse *pParse, SrcList *pName, int noErr){

   460   Trigger *pTrigger = 0;

   461   int i;

   462   const char *zDb;

   463   const char *zName;

   464   int nName;

   465   sqlite3 *db = pParse->db;

   466 

   467   if( db->mallocFailed ) goto drop_trigger_cleanup;

   468   if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){

   469     goto drop_trigger_cleanup;

   470   }

   471 

   472   assert( pName->nSrc==1 );

   473   zDb = pName->a[0].zDatabase;

   474   zName = pName->a[0].zName;

   475   nName = strlen(zName);

   476   for(i=OMIT_TEMPDB; i<db->nDb; i++){

   477     int j = (i<2) ? i^1 : i;  /* Search TEMP before MAIN */

   478     if( zDb && sqlite3StrICmp(db->aDb[j].zName, zDb) ) continue;

   479     pTrigger = (Trigger*)sqlite3HashFind(&(db->aDb[j].pSchema->trigHash), zName, nName);

   480     if( pTrigger ) break;

   481   }

   482   if( !pTrigger ){

   483     if( !noErr ){

   484       sqlite3ErrorMsg(pParse, "no such trigger: %S", pName, 0);

   485     }

   486     goto drop_trigger_cleanup;

   487   }

   488   sqlite3DropTriggerPtr(pParse, pTrigger);

   489 

   490 drop_trigger_cleanup:

   491   sqlite3SrcListDelete(pName);

   492 }

   493 

   494 /*

   495 ** Return a pointer to the Table structure for the table that a trigger

   496 ** is set on.

   497 */

   498 static Table *tableOfTrigger(Trigger *pTrigger){

   499   int n = strlen(pTrigger->table) + 1;

   500   return (Table*)sqlite3HashFind(&pTrigger->pTabSchema->tblHash, pTrigger->table, n);

   501 }

   502 

   503 

   504 /*

   505 ** Drop a trigger given a pointer to that trigger. 

   506 */

   507 void sqlite3DropTriggerPtr(Parse *pParse, Trigger *pTrigger){

   508   Table   *pTable;

   509   Vdbe *v;

   510   sqlite3 *db = pParse->db;

   511   int iDb;

   512 

   513   iDb = sqlite3SchemaToIndex(pParse->db, pTrigger->pSchema);

   514   assert( iDb>=0 && iDb<db->nDb );

   515   pTable = tableOfTrigger(pTrigger);

   516   assert( pTable );

   517   assert( pTable->pSchema==pTrigger->pSchema || iDb==1 );

   518 #ifndef SQLITE_OMIT_AUTHORIZATION

   519   {

   520     int code = SQLITE_DROP_TRIGGER;

   521     const char *zDb = db->aDb[iDb].zName;

   522     const char *zTab = SCHEMA_TABLE(iDb);

   523     if( iDb==1 ) code = SQLITE_DROP_TEMP_TRIGGER;

   524     if( sqlite3AuthCheck(pParse, code, pTrigger->name, pTable->zName, zDb) ||

   525       sqlite3AuthCheck(pParse, SQLITE_DELETE, zTab, 0, zDb) ){

   526       return;

   527     }

   528   }

   529 #endif

   530 

   531   /* Generate code to destroy the database record of the trigger.

   532   */

   533   assert( pTable!=0 );

   534   if( (v = sqlite3GetVdbe(pParse))!=0 ){

   535     int base;

   536     static const VdbeOpList dropTrigger[] = {

   537       { OP_Rewind,     0, ADDR(9),  0},

   538       { OP_String8,    0, 0,        0}, /* 1 */

   539       { OP_Column,     0, 1,        0},

   540       { OP_Ne,         0, ADDR(8),  0},

   541       { OP_String8,    0, 0,        "trigger"},

   542       { OP_Column,     0, 0,        0},

   543       { OP_Ne,         0, ADDR(8),  0},

   544       { OP_Delete,     0, 0,        0},

   545       { OP_Next,       0, ADDR(1),  0}, /* 8 */

   546     };

   547 

   548     sqlite3BeginWriteOperation(pParse, 0, iDb);

   549     sqlite3OpenMasterTable(pParse, iDb);

   550     base = sqlite3VdbeAddOpList(v,  ArraySize(dropTrigger), dropTrigger);

   551     sqlite3VdbeChangeP3(v, base+1, pTrigger->name, 0);

   552     sqlite3ChangeCookie(db, v, iDb);

   553     sqlite3VdbeAddOp(v, OP_Close, 0, 0);

   554     sqlite3VdbeOp3(v, OP_DropTrigger, iDb, 0, pTrigger->name, 0);

   555   }

   556 }

   557 

   558 /*

   559 ** Remove a trigger from the hash tables of the sqlite* pointer.

   560 */

   561 void sqlite3UnlinkAndDeleteTrigger(sqlite3 *db, int iDb, const char *zName){

   562   Trigger *pTrigger;

   563   int nName = strlen(zName);

   564   pTrigger = (Trigger*)sqlite3HashInsert(&(db->aDb[iDb].pSchema->trigHash),

   565                                zName, nName, 0);

   566   if( pTrigger ){

   567     Table *pTable = tableOfTrigger(pTrigger);

   568     assert( pTable!=0 );

   569     if( pTable->pTrigger == pTrigger ){

   570       pTable->pTrigger = pTrigger->pNext;

   571     }else{

   572       Trigger *cc = pTable->pTrigger;

   573       while( cc ){ 

   574         if( cc->pNext == pTrigger ){

   575           cc->pNext = cc->pNext->pNext;

   576           break;

   577         }

   578         cc = cc->pNext;

   579       }

   580       assert(cc);

   581     }

   582     sqlite3DeleteTrigger(pTrigger);

   583     db->flags |= SQLITE_InternChanges;

   584   }

   585 }

   586 

   587 /*

   588 ** pEList is the SET clause of an UPDATE statement.  Each entry

   589 ** in pEList is of the format <id>=<expr>.  If any of the entries

   590 ** in pEList have an <id> which matches an identifier in pIdList,

   591 ** then return TRUE.  If pIdList==NULL, then it is considered a

   592 ** wildcard that matches anything.  Likewise if pEList==NULL then

   593 ** it matches anything so always return true.  Return false only

   594 ** if there is no match.

   595 */

   596 static int checkColumnOverLap(IdList *pIdList, ExprList *pEList){

   597   int e;

   598   if( !pIdList || !pEList ) return 1;

   599   for(e=0; e<pEList->nExpr; e++){

   600     if( sqlite3IdListIndex(pIdList, pEList->a[e].zName)>=0 ) return 1;

   601   }

   602   return 0; 

   603 }

   604 

   605 /*

   606 ** Return a bit vector to indicate what kind of triggers exist for operation

   607 ** "op" on table pTab.  If pChanges is not NULL then it is a list of columns

   608 ** that are being updated.  Triggers only match if the ON clause of the

   609 ** trigger definition overlaps the set of columns being updated.

   610 **

   611 ** The returned bit vector is some combination of TRIGGER_BEFORE and

   612 ** TRIGGER_AFTER.

   613 */

   614 int sqlite3TriggersExist(

   615   Parse *pParse,          /* Used to check for recursive triggers */

   616   Table *pTab,            /* The table the contains the triggers */

   617   int op,                 /* one of TK_DELETE, TK_INSERT, TK_UPDATE */

   618   ExprList *pChanges      /* Columns that change in an UPDATE statement */

   619 ){

   620   Trigger *pTrigger;

   621   int mask = 0;

   622 

   623   pTrigger = IsVirtual(pTab) ? 0 : pTab->pTrigger;

   624   while( pTrigger ){

   625     if( pTrigger->op==op && checkColumnOverLap(pTrigger->pColumns, pChanges) ){

   626       mask |= pTrigger->tr_tm;

   627     }

   628     pTrigger = pTrigger->pNext;

   629   }

   630   return mask;

   631 }

   632 

   633 /*

   634 ** Convert the pStep->target token into a SrcList and return a pointer

   635 ** to that SrcList.

   636 **

   637 ** This routine adds a specific database name, if needed, to the target when

   638 ** forming the SrcList.  This prevents a trigger in one database from

   639 ** referring to a target in another database.  An exception is when the

   640 ** trigger is in TEMP in which case it can refer to any other database it

   641 ** wants.

   642 */

   643 static SrcList *targetSrcList(

   644   Parse *pParse,       /* The parsing context */

   645   TriggerStep *pStep   /* The trigger containing the target token */

   646 ){

   647   Token sDb;           /* Dummy database name token */

   648   int iDb;             /* Index of the database to use */

   649   SrcList *pSrc;       /* SrcList to be returned */

   650 

   651   iDb = sqlite3SchemaToIndex(pParse->db, pStep->pTrig->pSchema);

   652   if( iDb==0 || iDb>=2 ){

   653     assert( iDb<pParse->db->nDb );

   654     sDb.z = (u8*)pParse->db->aDb[iDb].zName;

   655     sDb.n = strlen((char*)sDb.z);

   656     pSrc = sqlite3SrcListAppend(pParse->db, 0, &sDb, &pStep->target);

   657   } else {

   658     pSrc = sqlite3SrcListAppend(pParse->db, 0, &pStep->target, 0);

   659   }

   660   return pSrc;

   661 }

   662 

   663 /*

   664 ** Generate VDBE code for zero or more statements inside the body of a

   665 ** trigger.  

   666 */

   667 static int codeTriggerProgram(

   668   Parse *pParse,            /* The parser context */

   669   TriggerStep *pStepList,   /* List of statements inside the trigger body */

   670   int orconfin              /* Conflict algorithm. (OE_Abort, etc) */  

   671 ){

   672   TriggerStep * pTriggerStep = pStepList;

   673   int orconf;

   674   Vdbe *v = pParse->pVdbe;

   675   sqlite3 *db = pParse->db;

   676 

   677   assert( pTriggerStep!=0 );

   678   assert( v!=0 );

   679   sqlite3VdbeAddOp(v, OP_ContextPush, 0, 0);

   680   VdbeComment((v, "# begin trigger %s", pStepList->pTrig->name));

   681   while( pTriggerStep ){

   682     orconf = (orconfin == OE_Default)?pTriggerStep->orconf:orconfin;

   683     pParse->trigStack->orconf = orconf;

   684     switch( pTriggerStep->op ){

   685       case TK_SELECT: {

   686         Select *ss = sqlite3SelectDup(db, pTriggerStep->pSelect);

   687         if( ss ){

   688           sqlite3SelectResolve(pParse, ss, 0);

   689           sqlite3Select(pParse, ss, SRT_Discard, 0, 0, 0, 0, 0);

   690           sqlite3SelectDelete(ss);

   691         }

   692         break;

   693       }

   694       case TK_UPDATE: {

   695         SrcList *pSrc;

   696         pSrc = targetSrcList(pParse, pTriggerStep);

   697         sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);

   698         sqlite3Update(pParse, pSrc,

   699                 sqlite3ExprListDup(db, pTriggerStep->pExprList), 

   700                 sqlite3ExprDup(db, pTriggerStep->pWhere), orconf);

   701         sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);

   702         break;

   703       }

   704       case TK_INSERT: {

   705         SrcList *pSrc;

   706         pSrc = targetSrcList(pParse, pTriggerStep);

   707         sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);

   708         sqlite3Insert(pParse, pSrc,

   709           sqlite3ExprListDup(db, pTriggerStep->pExprList), 

   710           sqlite3SelectDup(db, pTriggerStep->pSelect), 

   711           sqlite3IdListDup(db, pTriggerStep->pIdList), orconf);

   712         sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);

   713         break;

   714       }

   715       case TK_DELETE: {

   716         SrcList *pSrc;

   717         sqlite3VdbeAddOp(v, OP_ResetCount, 0, 0);

   718         pSrc = targetSrcList(pParse, pTriggerStep);

   719         sqlite3DeleteFrom(pParse, pSrc, 

   720                           sqlite3ExprDup(db, pTriggerStep->pWhere));

   721         sqlite3VdbeAddOp(v, OP_ResetCount, 1, 0);

   722         break;

   723       }

   724       default:

   725         assert(0);

   726     } 

   727     pTriggerStep = pTriggerStep->pNext;

   728   }

   729   sqlite3VdbeAddOp(v, OP_ContextPop, 0, 0);

   730   VdbeComment((v, "# end trigger %s", pStepList->pTrig->name));

   731 

   732   return 0;

   733 }

   734 

   735 /*

   736 ** This is called to code FOR EACH ROW triggers.

   737 **

   738 ** When the code that this function generates is executed, the following 

   739 ** must be true:

   740 **

   741 ** 1. No cursors may be open in the main database.  (But newIdx and oldIdx

   742 **    can be indices of cursors in temporary tables.  See below.)

   743 **

   744 ** 2. If the triggers being coded are ON INSERT or ON UPDATE triggers, then

   745 **    a temporary vdbe cursor (index newIdx) must be open and pointing at

   746 **    a row containing values to be substituted for new.* expressions in the

   747 **    trigger program(s).

   748 **

   749 ** 3. If the triggers being coded are ON DELETE or ON UPDATE triggers, then

   750 **    a temporary vdbe cursor (index oldIdx) must be open and pointing at

   751 **    a row containing values to be substituted for old.* expressions in the

   752 **    trigger program(s).

   753 **

   754 */

   755 int sqlite3CodeRowTrigger(

   756   Parse *pParse,       /* Parse context */

   757   int op,              /* One of TK_UPDATE, TK_INSERT, TK_DELETE */

   758   ExprList *pChanges,  /* Changes list for any UPDATE OF triggers */

   759   int tr_tm,           /* One of TRIGGER_BEFORE, TRIGGER_AFTER */

   760   Table *pTab,         /* The table to code triggers from */

   761   int newIdx,          /* The indice of the "new" row to access */

   762   int oldIdx,          /* The indice of the "old" row to access */

   763   int orconf,          /* ON CONFLICT policy */

   764   int ignoreJump       /* Instruction to jump to for RAISE(IGNORE) */

   765 ){

   766   Trigger *p;

   767   TriggerStack trigStackEntry;

   768 

   769   assert(op == TK_UPDATE || op == TK_INSERT || op == TK_DELETE);

   770   assert(tr_tm == TRIGGER_BEFORE || tr_tm == TRIGGER_AFTER );

   771 

   772   assert(newIdx != -1 || oldIdx != -1);

   773 

   774   for(p=pTab->pTrigger; p; p=p->pNext){

   775     int fire_this = 0;

   776     sqlite3 *db = pParse->db;

   777 

   778     /* Determine whether we should code this trigger */

   779     if( 

   780       p->op==op && 

   781       p->tr_tm==tr_tm && 

   782       (p->pSchema==p->pTabSchema || p->pSchema==db->aDb[1].pSchema) &&

   783       (op!=TK_UPDATE||!p->pColumns||checkColumnOverLap(p->pColumns,pChanges))

   784     ){

   785       TriggerStack *pS;      /* Pointer to trigger-stack entry */

   786       for(pS=pParse->trigStack; pS && p!=pS->pTrigger; pS=pS->pNext){}

   787       if( !pS ){

   788         fire_this = 1;

   789       }

   790 #if 0    /* Give no warning for recursive triggers.  Just do not do them */

   791       else{

   792         sqlite3ErrorMsg(pParse, "recursive triggers not supported (%s)",

   793             p->name);

   794         return SQLITE_ERROR;

   795       }

   796 #endif

   797     }

   798  

   799     if( fire_this ){

   800       int endTrigger;

   801       Expr * whenExpr;

   802       AuthContext sContext;

   803       NameContext sNC;

   804 

   805       memset(&sNC, 0, sizeof(sNC));

   806       sNC.pParse = pParse;

   807 

   808       /* Push an entry on to the trigger stack */

   809       trigStackEntry.pTrigger = p;

   810       trigStackEntry.newIdx = newIdx;

   811       trigStackEntry.oldIdx = oldIdx;

   812       trigStackEntry.pTab = pTab;

   813       trigStackEntry.pNext = pParse->trigStack;

   814       trigStackEntry.ignoreJump = ignoreJump;

   815       pParse->trigStack = &trigStackEntry;

   816       sqlite3AuthContextPush(pParse, &sContext, p->name);

   817 

   818       /* code the WHEN clause */

   819       endTrigger = sqlite3VdbeMakeLabel(pParse->pVdbe);

   820       whenExpr = sqlite3ExprDup(db, p->pWhen);

   821       if( db->mallocFailed || sqlite3ExprResolveNames(&sNC, whenExpr) ){

   822         pParse->trigStack = trigStackEntry.pNext;

   823         sqlite3ExprDelete(whenExpr);

   824         return 1;

   825       }

   826       sqlite3ExprIfFalse(pParse, whenExpr, endTrigger, 1);

   827       sqlite3ExprDelete(whenExpr);

   828 

   829       codeTriggerProgram(pParse, p->step_list, orconf); 

   830 

   831       /* Pop the entry off the trigger stack */

   832       pParse->trigStack = trigStackEntry.pNext;

   833       sqlite3AuthContextPop(&sContext);

   834 

   835       sqlite3VdbeResolveLabel(pParse->pVdbe, endTrigger);

   836     }

   837   }

   838   return 0;

   839 }

   840 #endif /* !defined(SQLITE_OMIT_TRIGGER) */