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   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 || sqlite3MallocFailed() ){

    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( sqlite3MallocFailed() ) 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(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     sqlite3ErrorMsg(pParse, "trigger %T already exists", pName);

   119     goto trigger_cleanup;

   120   }

   121 

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

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

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

   125     pParse->nErr++;

   126     goto trigger_cleanup;

   127   }

   128 

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

   130   ** of triggers.

   131   */

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

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

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

   135     goto trigger_cleanup;

   136   }

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

   138     sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"

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

   140     goto trigger_cleanup;

   141   }

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

   143 

   144 #ifndef SQLITE_OMIT_AUTHORIZATION

   145   {

   146     int code = SQLITE_CREATE_TRIGGER;

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

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

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

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

   151       goto trigger_cleanup;

   152     }

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

   154       goto trigger_cleanup;

   155     }

   156   }

   157 #endif

   158 

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

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

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

   162   ** elsewhere.

   163   */

   164   if (tr_tm == TK_INSTEAD){

   165     tr_tm = TK_BEFORE;

   166   }

   167 

   168   /* Build the Trigger object */

   169   pTrigger = (Trigger*)sqliteMalloc(sizeof(Trigger));

   170   if( pTrigger==0 ) goto trigger_cleanup;

   171   pTrigger->name = zName;

   172   zName = 0;

   173   pTrigger->table = sqliteStrDup(pTableName->a[0].zName);

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

   175   pTrigger->pTabSchema = pTab->pSchema;

   176   pTrigger->op = op;

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

   178   pTrigger->pWhen = sqlite3ExprDup(pWhen);

   179   pTrigger->pColumns = sqlite3IdListDup(pColumns);

   180   pTrigger->foreach = foreach;

   181   sqlite3TokenCopy(&pTrigger->nameToken,pName);

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

   183   pParse->pNewTrigger = pTrigger;

   184 

   185 trigger_cleanup:

   186   sqliteFree(zName);

   187   sqlite3SrcListDelete(pTableName);

   188   sqlite3IdListDelete(pColumns);

   189   sqlite3ExprDelete(pWhen);

   190   if( !pParse->pNewTrigger ){

   191     sqlite3DeleteTrigger(pTrigger);

   192   }else{

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

   194   }

   195 }

   196 

   197 /*

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

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

   200 */

   201 void sqlite3FinishTrigger(

   202   Parse *pParse,          /* Parser context */

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

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

   205 ){

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

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

   208   DbFixer sFix;

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

   210 

   211   pTrig = pParse->pNewTrigger;

   212   pParse->pNewTrigger = 0;

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

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

   215   pTrig->step_list = pStepList;

   216   while( pStepList ){

   217     pStepList->pTrig = pTrig;

   218     pStepList = pStepList->pNext;

   219   }

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

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

   222     goto triggerfinish_cleanup;

   223   }

   224 

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

   226   ** build the sqlite_master entry

   227   */

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

   229     static const VdbeOpList insertTrig[] = {

   230       { OP_NewRowid,   0, 0,  0          },

   231       { OP_String8,    0, 0,  "trigger"  },

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

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

   234       { OP_Integer,    0, 0,  0          },

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

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

   237       { OP_Concat,     0, 0,  0          }, 

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

   239       { OP_Insert,     0, 0,  0          },

   240     };

   241     int addr;

   242     Vdbe *v;

   243 

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

   245     v = sqlite3GetVdbe(pParse);

   246     if( v==0 ) goto triggerfinish_cleanup;

   247     sqlite3BeginWriteOperation(pParse, 0, iDb);

   248     sqlite3OpenMasterTable(pParse, iDb);

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

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

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

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

   253     sqlite3ChangeCookie(db, v, iDb);

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

   255     sqlite3VdbeOp3(v, OP_ParseSchema, iDb, 0, 

   256        sqlite3MPrintf("type='trigger' AND name='%q'", pTrig->name), P3_DYNAMIC);

   257   }

   258 

   259   if( db->init.busy ){

   260     int n;

   261     Table *pTab;

   262     Trigger *pDel;

   263     pDel = sqlite3HashInsert(&db->aDb[iDb].pSchema->trigHash, 

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

   265     if( pDel ){

   266       assert( sqlite3MallocFailed() && pDel==pTrig );

   267       goto triggerfinish_cleanup;

   268     }

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

   270     pTab = sqlite3HashFind(&pTrig->pTabSchema->tblHash, pTrig->table, n);

   271     assert( pTab!=0 );

   272     pTrig->pNext = pTab->pTrigger;

   273     pTab->pTrigger = pTrig;

   274     pTrig = 0;

   275   }

   276 

   277 triggerfinish_cleanup:

   278   sqlite3DeleteTrigger(pTrig);

   279   assert( !pParse->pNewTrigger );

   280   sqlite3DeleteTriggerStep(pStepList);

   281 }

   282 

   283 /*

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

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

   286 ** from sqliteMalloc().  As initially created, the Expr.token.z values

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

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

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

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

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

   292 */

   293 static void sqlitePersistTriggerStep(TriggerStep *p){

   294   if( p->target.z ){

   295     p->target.z = (u8*)sqliteStrNDup((char*)p->target.z, p->target.n);

   296     p->target.dyn = 1;

   297   }

   298   if( p->pSelect ){

   299     Select *pNew = sqlite3SelectDup(p->pSelect);

   300     sqlite3SelectDelete(p->pSelect);

   301     p->pSelect = pNew;

   302   }

   303   if( p->pWhere ){

   304     Expr *pNew = sqlite3ExprDup(p->pWhere);

   305     sqlite3ExprDelete(p->pWhere);

   306     p->pWhere = pNew;

   307   }

   308   if( p->pExprList ){

   309     ExprList *pNew = sqlite3ExprListDup(p->pExprList);

   310     sqlite3ExprListDelete(p->pExprList);

   311     p->pExprList = pNew;

   312   }

   313   if( p->pIdList ){

   314     IdList *pNew = sqlite3IdListDup(p->pIdList);

   315     sqlite3IdListDelete(p->pIdList);

   316     p->pIdList = pNew;

   317   }

   318 }

   319 

   320 /*

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

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

   323 **

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

   325 ** body of a TRIGGER.  

   326 */

   327 TriggerStep *sqlite3TriggerSelectStep(Select *pSelect){

   328   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));

   329   if( pTriggerStep==0 ) {

   330     sqlite3SelectDelete(pSelect);

   331     return 0;

   332   }

   333 

   334   pTriggerStep->op = TK_SELECT;

   335   pTriggerStep->pSelect = pSelect;

   336   pTriggerStep->orconf = OE_Default;

   337   sqlitePersistTriggerStep(pTriggerStep);

   338 

   339   return pTriggerStep;

   340 }

   341 

   342 /*

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

   344 ** to the new trigger step.

   345 **

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

   347 ** body of a trigger.

   348 */

   349 TriggerStep *sqlite3TriggerInsertStep(

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

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

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

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

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

   355 ){

   356   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));

   357 

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

   359   assert(pEList != 0 || pSelect != 0);

   360 

   361   if( pTriggerStep ){

   362     pTriggerStep->op = TK_INSERT;

   363     pTriggerStep->pSelect = pSelect;

   364     pTriggerStep->target  = *pTableName;

   365     pTriggerStep->pIdList = pColumn;

   366     pTriggerStep->pExprList = pEList;

   367     pTriggerStep->orconf = orconf;

   368     sqlitePersistTriggerStep(pTriggerStep);

   369   }else{

   370     sqlite3IdListDelete(pColumn);

   371     sqlite3ExprListDelete(pEList);

   372     sqlite3SelectDup(pSelect);

   373   }

   374 

   375   return pTriggerStep;

   376 }

   377 

   378 /*

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

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

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

   382 */

   383 TriggerStep *sqlite3TriggerUpdateStep(

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

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

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

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

   388 ){

   389   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));

   390   if( pTriggerStep==0 ) return 0;

   391 

   392   pTriggerStep->op = TK_UPDATE;

   393   pTriggerStep->target  = *pTableName;

   394   pTriggerStep->pExprList = pEList;

   395   pTriggerStep->pWhere = pWhere;

   396   pTriggerStep->orconf = orconf;

   397   sqlitePersistTriggerStep(pTriggerStep);

   398 

   399   return pTriggerStep;

   400 }

   401 

   402 /*

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

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

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

   406 */

   407 TriggerStep *sqlite3TriggerDeleteStep(Token *pTableName, Expr *pWhere){

   408   TriggerStep *pTriggerStep = sqliteMalloc(sizeof(TriggerStep));

   409   if( pTriggerStep==0 ) return 0;

   410 

   411   pTriggerStep->op = TK_DELETE;

   412   pTriggerStep->target  = *pTableName;

   413   pTriggerStep->pWhere = pWhere;

   414   pTriggerStep->orconf = OE_Default;

   415   sqlitePersistTriggerStep(pTriggerStep);

   416 

   417   return pTriggerStep;

   418 }

   419 

   420 /* 

   421 ** Recursively delete a Trigger structure

   422 */

   423 void sqlite3DeleteTrigger(Trigger *pTrigger){

   424   if( pTrigger==0 ) return;

   425   sqlite3DeleteTriggerStep(pTrigger->step_list);

   426   sqliteFree(pTrigger->name);

   427   sqliteFree(pTrigger->table);

   428   sqlite3ExprDelete(pTrigger->pWhen);

   429   sqlite3IdListDelete(pTrigger->pColumns);

   430   if( pTrigger->nameToken.dyn ) sqliteFree((char*)pTrigger->nameToken.z);

   431   sqliteFree(pTrigger);

   432 }

   433 

   434 /*

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

   436 **

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

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

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

   440 ** instead of the trigger name.

   441 **/

   442 void sqlite3DropTrigger(Parse *pParse, SrcList *pName){

   443   Trigger *pTrigger = 0;

   444   int i;

   445   const char *zDb;

   446   const char *zName;

   447   int nName;

   448   sqlite3 *db = pParse->db;

   449 

   450   if( sqlite3MallocFailed() ) goto drop_trigger_cleanup;

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

   452     goto drop_trigger_cleanup;

   453   }

   454 

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

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

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

   458   nName = strlen(zName);

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

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

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

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

   463     if( pTrigger ) break;

   464   }

   465   if( !pTrigger ){

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

   467     goto drop_trigger_cleanup;

   468   }

   469   sqlite3DropTriggerPtr(pParse, pTrigger);

   470 

   471 drop_trigger_cleanup:

   472   sqlite3SrcListDelete(pName);

   473 }

   474 

   475 /*

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

   477 ** is set on.

   478 */

   479 static Table *tableOfTrigger(Trigger *pTrigger){

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

   481   return sqlite3HashFind(&pTrigger->pTabSchema->tblHash, pTrigger->table, n);

   482 }

   483 

   484 

   485 /*

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

   487 */

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

   489   Table   *pTable;

   490   Vdbe *v;

   491   sqlite3 *db = pParse->db;

   492   int iDb;

   493 

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

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

   496   pTable = tableOfTrigger(pTrigger);

   497   assert( pTable );

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

   499 #ifndef SQLITE_OMIT_AUTHORIZATION

   500   {

   501     int code = SQLITE_DROP_TRIGGER;

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

   503     const char *zTab = SCHEMA_TABLE(iDb);

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

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

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

   507       return;

   508     }

   509   }

   510 #endif

   511 

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

   513   */

   514   assert( pTable!=0 );

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

   516     int base;

   517     static const VdbeOpList dropTrigger[] = {

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

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

   520       { OP_Column,     0, 1,        0},

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

   522       { OP_String8,    0, 0,        "trigger"},

   523       { OP_Column,     0, 0,        0},

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

   525       { OP_Delete,     0, 0,        0},

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

   527     };

   528 

   529     sqlite3BeginWriteOperation(pParse, 0, iDb);

   530     sqlite3OpenMasterTable(pParse, iDb);

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

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

   533     sqlite3ChangeCookie(db, v, iDb);

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

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

   536   }

   537 }

   538 

   539 /*

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

   541 */

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

   543   Trigger *pTrigger;

   544   int nName = strlen(zName);

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

   546                                zName, nName, 0);

   547   if( pTrigger ){

   548     Table *pTable = tableOfTrigger(pTrigger);

   549     assert( pTable!=0 );

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

   551       pTable->pTrigger = pTrigger->pNext;

   552     }else{

   553       Trigger *cc = pTable->pTrigger;

   554       while( cc ){ 

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

   556           cc->pNext = cc->pNext->pNext;

   557           break;

   558         }

   559         cc = cc->pNext;

   560       }

   561       assert(cc);

   562     }

   563     sqlite3DeleteTrigger(pTrigger);

   564     db->flags |= SQLITE_InternChanges;

   565   }

   566 }

   567 

   568 /*

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

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

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

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

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

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

   575 ** if there is no match.

   576 */

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

   578   int e;

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

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

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

   582   }

   583   return 0; 

   584 }

   585 

   586 /*

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

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

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

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

   591 **

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

   593 ** TRIGGER_AFTER.

   594 */

   595 int sqlite3TriggersExist(

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

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

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

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

   600 ){

   601   Trigger *pTrigger;

   602   int mask = 0;

   603 

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

   605   while( pTrigger ){

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

   607       mask |= pTrigger->tr_tm;

   608     }

   609     pTrigger = pTrigger->pNext;

   610   }

   611   return mask;

   612 }

   613 

   614 /*

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

   616 ** to that SrcList.

   617 **

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

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

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

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

   622 ** wants.

   623 */

   624 static SrcList *targetSrcList(

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

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

   627 ){

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

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

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

   631 

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

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

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

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

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

   637     pSrc = sqlite3SrcListAppend(0, &sDb, &pStep->target);

   638   } else {

   639     pSrc = sqlite3SrcListAppend(0, &pStep->target, 0);

   640   }

   641   return pSrc;

   642 }

   643 

   644 /*

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

   646 ** trigger.  

   647 */

   648 static int codeTriggerProgram(

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

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

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

   652 ){

   653   TriggerStep * pTriggerStep = pStepList;

   654   int orconf;

   655   Vdbe *v = pParse->pVdbe;

   656 

   657   assert( pTriggerStep!=0 );

   658   assert( v!=0 );

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

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

   661   while( pTriggerStep ){

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

   663     pParse->trigStack->orconf = orconf;

   664     switch( pTriggerStep->op ){

   665       case TK_SELECT: {

   666 	Select * ss = sqlite3SelectDup(pTriggerStep->pSelect);		  

   667 	assert(ss);

   668 	assert(ss->pSrc);

   669         sqlite3SelectResolve(pParse, ss, 0);

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

   671 	sqlite3SelectDelete(ss);

   672 	break;

   673       }

   674       case TK_UPDATE: {

   675         SrcList *pSrc;

   676         pSrc = targetSrcList(pParse, pTriggerStep);

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

   678         sqlite3Update(pParse, pSrc,

   679 		sqlite3ExprListDup(pTriggerStep->pExprList), 

   680 		sqlite3ExprDup(pTriggerStep->pWhere), orconf);

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

   682         break;

   683       }

   684       case TK_INSERT: {

   685         SrcList *pSrc;

   686         pSrc = targetSrcList(pParse, pTriggerStep);

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

   688         sqlite3Insert(pParse, pSrc,

   689           sqlite3ExprListDup(pTriggerStep->pExprList), 

   690           sqlite3SelectDup(pTriggerStep->pSelect), 

   691           sqlite3IdListDup(pTriggerStep->pIdList), orconf);

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

   693         break;

   694       }

   695       case TK_DELETE: {

   696         SrcList *pSrc;

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

   698         pSrc = targetSrcList(pParse, pTriggerStep);

   699         sqlite3DeleteFrom(pParse, pSrc, sqlite3ExprDup(pTriggerStep->pWhere));

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

   701         break;

   702       }

   703       default:

   704         assert(0);

   705     } 

   706     pTriggerStep = pTriggerStep->pNext;

   707   }

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

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

   710 

   711   return 0;

   712 }

   713 

   714 /*

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

   716 **

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

   718 ** must be true:

   719 **

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

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

   722 **

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

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

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

   726 **    trigger program(s).

   727 **

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

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

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

   731 **    trigger program(s).

   732 **

   733 */

   734 int sqlite3CodeRowTrigger(

   735   Parse *pParse,       /* Parse context */

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

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

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

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

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

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

   742   int orconf,          /* ON CONFLICT policy */

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

   744 ){

   745   Trigger *p;

   746   TriggerStack trigStackEntry;

   747 

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

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

   750 

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

   752 

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

   754     int fire_this = 0;

   755 

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

   757     if( 

   758       p->op==op && 

   759       p->tr_tm==tr_tm && 

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

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

   762     ){

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

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

   765       if( !pS ){

   766         fire_this = 1;

   767       }

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

   769       else{

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

   771             p->name);

   772         return SQLITE_ERROR;

   773       }

   774 #endif

   775     }

   776  

   777     if( fire_this ){

   778       int endTrigger;

   779       Expr * whenExpr;

   780       AuthContext sContext;

   781       NameContext sNC;

   782 

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

   784       sNC.pParse = pParse;

   785 

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

   787       trigStackEntry.pTrigger = p;

   788       trigStackEntry.newIdx = newIdx;

   789       trigStackEntry.oldIdx = oldIdx;

   790       trigStackEntry.pTab = pTab;

   791       trigStackEntry.pNext = pParse->trigStack;

   792       trigStackEntry.ignoreJump = ignoreJump;

   793       pParse->trigStack = &trigStackEntry;

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

   795 

   796       /* code the WHEN clause */

   797       endTrigger = sqlite3VdbeMakeLabel(pParse->pVdbe);

   798       whenExpr = sqlite3ExprDup(p->pWhen);

   799       if( sqlite3ExprResolveNames(&sNC, whenExpr) ){

   800         pParse->trigStack = trigStackEntry.pNext;

   801         sqlite3ExprDelete(whenExpr);

   802         return 1;

   803       }

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

   805       sqlite3ExprDelete(whenExpr);

   806 

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

   808 

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

   810       pParse->trigStack = trigStackEntry.pNext;

   811       sqlite3AuthContextPop(&sContext);

   812 

   813       sqlite3VdbeResolveLabel(pParse->pVdbe, endTrigger);

   814     }

   815   }

   816   return 0;

   817 }

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