/*

 **

 ** The author disclaims copyright to this source code.  In place of

 ** a legal notice, here is a blessing:

 **

 **    May you do good and not evil.

 **    May you find forgiveness for yourself and forgive others.

 **    May you share freely, never taking more than you give.

 **

 *************************************************************************

 **

 **

 ** $Id: trigger.c,v 1.129 2008/08/20 16:35:10 drh Exp $

 */

 #include "sqliteInt.h"

 #ifndef SQLITE_OMIT_TRIGGER

 /*

 ** Delete a linked list of TriggerStep structures.

 */

 void sqlite3DeleteTriggerStep(sqlite3 *db, TriggerStep *pTriggerStep){

   while( pTriggerStep ){

     TriggerStep * pTmp = pTriggerStep;

     pTriggerStep = pTriggerStep->pNext;

     if( pTmp->target.dyn ) sqlite3DbFree(db, (char*)pTmp->target.z);

     sqlite3ExprDelete(db, pTmp->pWhere);

     sqlite3ExprListDelete(db, pTmp->pExprList);

     sqlite3SelectDelete(db, pTmp->pSelect);

     sqlite3IdListDelete(db, pTmp->pIdList);

     sqlite3DbFree(db, pTmp);

   }

 }

 /*

 ** This is called by the parser when it sees a CREATE TRIGGER statement

 ** up to the point of the BEGIN before the trigger actions.  A Trigger

 ** structure is generated based on the information available and stored

 ** in pParse->pNewTrigger.  After the trigger actions have been parsed, the

 ** sqlite3FinishTrigger() function is called to complete the trigger

 ** construction process.

 */

 void sqlite3BeginTrigger(

   Parse *pParse,      /* The parse context of the CREATE TRIGGER statement */

   Token *pName1,      /* The name of the trigger */

   Token *pName2,      /* The name of the trigger */

   int tr_tm,          /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD */

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

   IdList *pColumns,   /* column list if this is an UPDATE OF trigger */

   SrcList *pTableName,/* The name of the table/view the trigger applies to */

   Expr *pWhen,        /* WHEN clause */

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

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

 ){

   Trigger *pTrigger = 0;

   Table *pTab;

   char *zName = 0;        /* Name of the trigger */

   sqlite3 *db = pParse->db;

   int iDb;                /* The database to store the trigger in */

   Token *pName;           /* The unqualified db name */

   DbFixer sFix;

   int iTabDb;

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

   assert( pName2!=0 );

   if( isTemp ){

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

     if( pName2->n>0 ){

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

       goto trigger_cleanup;

     }

     iDb = 1;

     pName = pName1;

   }else{

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

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

     if( iDb<0 ){

       goto trigger_cleanup;

     }

   }

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

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

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

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

   */

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

     goto trigger_cleanup;

   }

   pTab = sqlite3SrcListLookup(pParse, pTableName);

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

     iDb = 1;

   }

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

   if( db->mallocFailed ) goto trigger_cleanup;

   assert( pTableName->nSrc==1 );

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

       sqlite3FixSrcList(&sFix, pTableName) ){

     goto trigger_cleanup;

   }

   pTab = sqlite3SrcListLookup(pParse, pTableName);

   if( !pTab ){

     /* The table does not exist. */

     goto trigger_cleanup;

   }

   if( IsVirtual(pTab) ){

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

     goto trigger_cleanup;

   }

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

   ** specified name exists */

   zName = sqlite3NameFromToken(db, pName);

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

     goto trigger_cleanup;

   }

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

     if( !noErr ){

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

     }

     goto trigger_cleanup;

   }

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

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

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

     pParse->nErr++;

     goto trigger_cleanup;

   }

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

   ** of triggers.

   */

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

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

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

     goto trigger_cleanup;

   }

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

     sqlite3ErrorMsg(pParse, "cannot create INSTEAD OF"

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

     goto trigger_cleanup;

   }

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

 #ifndef SQLITE_OMIT_AUTHORIZATION

   {

     int code = SQLITE_CREATE_TRIGGER;

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

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

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

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

       goto trigger_cleanup;

     }

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

       goto trigger_cleanup;

     }

   }

 #endif

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

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

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

   ** elsewhere.

   */

   if (tr_tm == TK_INSTEAD){

     tr_tm = TK_BEFORE;

   }

   /* Build the Trigger object */

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

   if( pTrigger==0 ) goto trigger_cleanup;

   pTrigger->name = zName;

   zName = 0;

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

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

   pTrigger->pTabSchema = pTab->pSchema;

   pTrigger->op = op;

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

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

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

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

   assert( pParse->pNewTrigger==0 );

   pParse->pNewTrigger = pTrigger;

 trigger_cleanup:

   sqlite3DbFree(db, zName);

   sqlite3SrcListDelete(db, pTableName);

   sqlite3IdListDelete(db, pColumns);

   sqlite3ExprDelete(db, pWhen);

   if( !pParse->pNewTrigger ){

     sqlite3DeleteTrigger(db, pTrigger);

   }else{

     assert( pParse->pNewTrigger==pTrigger );

   }

 }

 /*

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

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

 */

 void sqlite3FinishTrigger(

   Parse *pParse,          /* Parser context */

   TriggerStep *pStepList, /* The triggered program */

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

 ){

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

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

   DbFixer sFix;

   int iDb;                   /* Database containing the trigger */

   pTrig = pParse->pNewTrigger;

   pParse->pNewTrigger = 0;

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

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

   pTrig->step_list = pStepList;

   while( pStepList ){

     pStepList->pTrig = pTrig;

     pStepList = pStepList->pNext;

   }

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

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

     goto triggerfinish_cleanup;

   }

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

   ** build the sqlite_master entry

   */

   if( !db->init.busy ){

     Vdbe *v;

     char *z;

     /* Make an entry in the sqlite_master table */

     v = sqlite3GetVdbe(pParse);

     if( v==0 ) goto triggerfinish_cleanup;

     sqlite3BeginWriteOperation(pParse, 0, iDb);

     z = sqlite3DbStrNDup(db, (char*)pAll->z, pAll->n);

     sqlite3NestedParse(pParse,

        "INSERT INTO %Q.%s VALUES('trigger',%Q,%Q,0,'CREATE TRIGGER %q')",

        db->aDb[iDb].zName, SCHEMA_TABLE(iDb), pTrig->name,

        pTrig->table, z);

     sqlite3DbFree(db, z);

     sqlite3ChangeCookie(pParse, iDb);

     sqlite3VdbeAddOp4(v, OP_ParseSchema, iDb, 0, 0, sqlite3MPrintf(

         db, "type='trigger' AND name='%q'", pTrig->name), P4_DYNAMIC

     );

   }

   if( db->init.busy ){

     int n;

     Table *pTab;

     Trigger *pDel;

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

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

     if( pDel ){

       assert( pDel==pTrig );

       db->mallocFailed = 1;

       goto triggerfinish_cleanup;

     }

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

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

     assert( pTab!=0 );

     pTrig->pNext = pTab->pTrigger;

     pTab->pTrigger = pTrig;

     pTrig = 0;

   }

 triggerfinish_cleanup:

   sqlite3DeleteTrigger(db, pTrig);

   assert( !pParse->pNewTrigger );

   sqlite3DeleteTriggerStep(db, pStepList);

 }

 /*

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

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

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

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

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

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

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

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

 */

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

   if( p->target.z ){

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

     p->target.dyn = 1;

   }

   if( p->pSelect ){

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

     sqlite3SelectDelete(db, p->pSelect);

     p->pSelect = pNew;

   }

   if( p->pWhere ){

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

     sqlite3ExprDelete(db, p->pWhere);

     p->pWhere = pNew;

   }

   if( p->pExprList ){

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

     sqlite3ExprListDelete(db, p->pExprList);

     p->pExprList = pNew;

   }

   if( p->pIdList ){

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

     sqlite3IdListDelete(db, p->pIdList);

     p->pIdList = pNew;

   }

 }

 /*

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

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

 **

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

 ** body of a TRIGGER.  

 */

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

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

   if( pTriggerStep==0 ) {

     sqlite3SelectDelete(db, pSelect);

     return 0;

   }

   pTriggerStep->op = TK_SELECT;

   pTriggerStep->pSelect = pSelect;

   pTriggerStep->orconf = OE_Default;

   sqlitePersistTriggerStep(db, pTriggerStep);

   return pTriggerStep;

 }

 /*

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

 ** to the new trigger step.

 **

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

 ** body of a trigger.

 */

 TriggerStep *sqlite3TriggerInsertStep(

   sqlite3 *db,        /* The database connection */

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

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

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

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

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

 ){

   TriggerStep *pTriggerStep;

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

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

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

   if( pTriggerStep ){

     pTriggerStep->op = TK_INSERT;

     pTriggerStep->pSelect = pSelect;

     pTriggerStep->target  = *pTableName;

     pTriggerStep->pIdList = pColumn;

     pTriggerStep->pExprList = pEList;

     pTriggerStep->orconf = orconf;

     sqlitePersistTriggerStep(db, pTriggerStep);

   }else{

     sqlite3IdListDelete(db, pColumn);

     sqlite3ExprListDelete(db, pEList);

     sqlite3SelectDelete(db, pSelect);

   }

   return pTriggerStep;

 }

 /*

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

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

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

 */

 TriggerStep *sqlite3TriggerUpdateStep(

   sqlite3 *db,         /* The database connection */

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

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

   Expr *pWhere,        /* The WHERE clause */

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

 ){

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

   if( pTriggerStep==0 ){

      sqlite3ExprListDelete(db, pEList);

      sqlite3ExprDelete(db, pWhere);

      return 0;

   }

   pTriggerStep->op = TK_UPDATE;

   pTriggerStep->target  = *pTableName;

   pTriggerStep->pExprList = pEList;

   pTriggerStep->pWhere = pWhere;

   pTriggerStep->orconf = orconf;

   sqlitePersistTriggerStep(db, pTriggerStep);

   return pTriggerStep;

 }

 /*

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

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

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

 */

 TriggerStep *sqlite3TriggerDeleteStep(

   sqlite3 *db,            /* Database connection */

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

   Expr *pWhere            /* The WHERE clause */

 ){

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

   if( pTriggerStep==0 ){

     sqlite3ExprDelete(db, pWhere);

     return 0;

   }

   pTriggerStep->op = TK_DELETE;

   pTriggerStep->target  = *pTableName;

   pTriggerStep->pWhere = pWhere;

   pTriggerStep->orconf = OE_Default;

   sqlitePersistTriggerStep(db, pTriggerStep);

   return pTriggerStep;

 }

 /* 

 ** Recursively delete a Trigger structure

 */

 void sqlite3DeleteTrigger(sqlite3 *db, Trigger *pTrigger){

   if( pTrigger==0 ) return;

   sqlite3DeleteTriggerStep(db, pTrigger->step_list);

   sqlite3DbFree(db, pTrigger->name);

   sqlite3DbFree(db, pTrigger->table);

   sqlite3ExprDelete(db, pTrigger->pWhen);

   sqlite3IdListDelete(db, pTrigger->pColumns);

   if( pTrigger->nameToken.dyn ) sqlite3DbFree(db, (char*)pTrigger->nameToken.z);

   sqlite3DbFree(db, pTrigger);

 }

 /*

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

 **

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

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

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

 ** instead of the trigger name.

 **/

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

   Trigger *pTrigger = 0;

   int i;

   const char *zDb;

   const char *zName;

   int nName;

   sqlite3 *db = pParse->db;

   if( db->mallocFailed ) goto drop_trigger_cleanup;

   if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){

     goto drop_trigger_cleanup;

   }

   assert( pName->nSrc==1 );

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

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

   nName = strlen(zName);

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

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

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

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

     if( pTrigger ) break;

   }

   if( !pTrigger ){

     if( !noErr ){

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

     }

     goto drop_trigger_cleanup;

   }

   sqlite3DropTriggerPtr(pParse, pTrigger);

 drop_trigger_cleanup:

   sqlite3SrcListDelete(db, pName);

 }

 /*

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

 ** is set on.

 */

 static Table *tableOfTrigger(Trigger *pTrigger){

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

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

 }

 /*

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

 */

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

   Table   *pTable;

   Vdbe *v;

   sqlite3 *db = pParse->db;

   int iDb;

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

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

   pTable = tableOfTrigger(pTrigger);

   assert( pTable );

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

 #ifndef SQLITE_OMIT_AUTHORIZATION

   {

     int code = SQLITE_DROP_TRIGGER;

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

     const char *zTab = SCHEMA_TABLE(iDb);

     if( iDb==1 ) code = SQLITE_DROP_TEMP_TRIGGER;

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

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

       return;

     }

   }

 #endif

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

   */

   assert( pTable!=0 );

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

     int base;

     static const VdbeOpList dropTrigger[] = {

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

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

       { OP_Column,     0, 1,        2},

       { OP_Ne,         2, ADDR(8),  1},

       { OP_String8,    0, 1,        0}, /* 4: "trigger" */

       { OP_Column,     0, 0,        2},

       { OP_Ne,         2, ADDR(8),  1},

       { OP_Delete,     0, 0,        0},

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

     };

     sqlite3BeginWriteOperation(pParse, 0, iDb);

     sqlite3OpenMasterTable(pParse, iDb);

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

     sqlite3VdbeChangeP4(v, base+1, pTrigger->name, 0);

     sqlite3VdbeChangeP4(v, base+4, "trigger", P4_STATIC);

     sqlite3ChangeCookie(pParse, iDb);

     sqlite3VdbeAddOp2(v, OP_Close, 0, 0);

     sqlite3VdbeAddOp4(v, OP_DropTrigger, iDb, 0, 0, pTrigger->name, 0);

   }

 }

 /*

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

 */

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

   Trigger *pTrigger;

   int nName = strlen(zName);

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

                                zName, nName, 0);

   if( pTrigger ){

     Table *pTable = tableOfTrigger(pTrigger);

     assert( pTable!=0 );

     if( pTable->pTrigger == pTrigger ){

       pTable->pTrigger = pTrigger->pNext;

     }else{

       Trigger *cc = pTable->pTrigger;

       while( cc ){ 

         if( cc->pNext == pTrigger ){

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

           break;

         }

         cc = cc->pNext;

       }

       assert(cc);

     }

     sqlite3DeleteTrigger(db, pTrigger);

     db->flags |= SQLITE_InternChanges;

   }

 }

 /*

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

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

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

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

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

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

 ** if there is no match.

 */

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

   int e;

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

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

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

   }

   return 0; 

 }

 /*

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

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

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

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

 **

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

 ** TRIGGER_AFTER.

 */

 int sqlite3TriggersExist(

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

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

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

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

 ){

   Trigger *pTrigger;

   int mask = 0;

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

   while( pTrigger ){

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

       mask |= pTrigger->tr_tm;

     }

     pTrigger = pTrigger->pNext;

   }

   return mask;

 }

 /*

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

 ** to that SrcList.

 **

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

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

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

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

 ** wants.

 */

 static SrcList *targetSrcList(

   Parse *pParse,       /* The parsing context */

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

 ){

   Token sDb;           /* Dummy database name token */

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

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

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

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

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

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

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

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

   } else {

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

   }

   return pSrc;

 }

 /*

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

 ** trigger.  

 */

 static int codeTriggerProgram(

   Parse *pParse,            /* The parser context */

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

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

 ){

   TriggerStep * pTriggerStep = pStepList;

   int orconf;

   Vdbe *v = pParse->pVdbe;

   sqlite3 *db = pParse->db;

   assert( pTriggerStep!=0 );

   assert( v!=0 );

   sqlite3VdbeAddOp2(v, OP_ContextPush, 0, 0);

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

   while( pTriggerStep ){

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

     pParse->trigStack->orconf = orconf;

     switch( pTriggerStep->op ){

       case TK_SELECT: {

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

         if( ss ){

           SelectDest dest;

           sqlite3SelectDestInit(&dest, SRT_Discard, 0);

           sqlite3Select(pParse, ss, &dest);

           sqlite3SelectDelete(db, ss);

         }

         break;

       }

       case TK_UPDATE: {

         SrcList *pSrc;

         pSrc = targetSrcList(pParse, pTriggerStep);

         sqlite3VdbeAddOp2(v, OP_ResetCount, 0, 0);

         sqlite3Update(pParse, pSrc,

                 sqlite3ExprListDup(db, pTriggerStep->pExprList), 

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

         sqlite3VdbeAddOp2(v, OP_ResetCount, 1, 0);

         break;

       }

       case TK_INSERT: {

         SrcList *pSrc;

         pSrc = targetSrcList(pParse, pTriggerStep);

         sqlite3VdbeAddOp2(v, OP_ResetCount, 0, 0);

         sqlite3Insert(pParse, pSrc,

           sqlite3ExprListDup(db, pTriggerStep->pExprList), 

           sqlite3SelectDup(db, pTriggerStep->pSelect), 

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

         sqlite3VdbeAddOp2(v, OP_ResetCount, 1, 0);

         break;

       }

       case TK_DELETE: {

         SrcList *pSrc;

         sqlite3VdbeAddOp2(v, OP_ResetCount, 0, 0);

         pSrc = targetSrcList(pParse, pTriggerStep);

         sqlite3DeleteFrom(pParse, pSrc, 

                           sqlite3ExprDup(db, pTriggerStep->pWhere));

         sqlite3VdbeAddOp2(v, OP_ResetCount, 1, 0);

         break;

       }

       default:

         assert(0);

     } 

     pTriggerStep = pTriggerStep->pNext;

   }

   sqlite3VdbeAddOp2(v, OP_ContextPop, 0, 0);

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

   return 0;

 }

 /*

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

 **

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

 ** must be true:

 **

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

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

 **

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

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

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

 **    trigger program(s).

 **

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

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

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

 **    trigger program(s).

 **

 ** If they are not NULL, the piOldColMask and piNewColMask output variables

 ** are set to values that describe the columns used by the trigger program

 ** in the OLD.* and NEW.* tables respectively. If column N of the 

 ** pseudo-table is read at least once, the corresponding bit of the output

 ** mask is set. If a column with an index greater than 32 is read, the

 ** output mask is set to the special value 0xffffffff.

 **

 */

 int sqlite3CodeRowTrigger(

   Parse *pParse,       /* Parse context */

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

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

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

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

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

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

   int orconf,          /* ON CONFLICT policy */

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

   u32 *piOldColMask,   /* OUT: Mask of columns used from the OLD.* table */

   u32 *piNewColMask    /* OUT: Mask of columns used from the NEW.* table */

 ){

   Trigger *p;

   sqlite3 *db = pParse->db;

   TriggerStack trigStackEntry;

   trigStackEntry.oldColMask = 0;

   trigStackEntry.newColMask = 0;

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

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

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

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

     int fire_this = 0;

     /* Determine whether we should code this trigger */

     if( 

       p->op==op && 

       p->tr_tm==tr_tm && 

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

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

     ){

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

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

       if( !pS ){

         fire_this = 1;

       }

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

       else{

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

             p->name);

         return SQLITE_ERROR;

       }

 #endif

     }

     if( fire_this ){

       int endTrigger;

       Expr * whenExpr;

       AuthContext sContext;

       NameContext sNC;

 #ifndef SQLITE_OMIT_TRACE

       sqlite3VdbeAddOp4(pParse->pVdbe, OP_Trace, 0, 0, 0,

                         sqlite3MPrintf(db, "-- TRIGGER %s", p->name),

                         P4_DYNAMIC);

 #endif

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

       sNC.pParse = pParse;

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

       trigStackEntry.pTrigger = p;

       trigStackEntry.newIdx = newIdx;

       trigStackEntry.oldIdx = oldIdx;

       trigStackEntry.pTab = pTab;

       trigStackEntry.pNext = pParse->trigStack;

       trigStackEntry.ignoreJump = ignoreJump;

       pParse->trigStack = &trigStackEntry;

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

       /* code the WHEN clause */

       endTrigger = sqlite3VdbeMakeLabel(pParse->pVdbe);

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

       if( db->mallocFailed || sqlite3ResolveExprNames(&sNC, whenExpr) ){

         pParse->trigStack = trigStackEntry.pNext;

         sqlite3ExprDelete(db, whenExpr);

         return 1;

       }

       sqlite3ExprIfFalse(pParse, whenExpr, endTrigger, SQLITE_JUMPIFNULL);

       sqlite3ExprDelete(db, whenExpr);

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

       /* Pop the entry off the trigger stack */

       pParse->trigStack = trigStackEntry.pNext;

       sqlite3AuthContextPop(&sContext);

       sqlite3VdbeResolveLabel(pParse->pVdbe, endTrigger);

     }

   }

   if( piOldColMask ) *piOldColMask |= trigStackEntry.oldColMask;

   if( piNewColMask ) *piNewColMask |= trigStackEntry.newColMask;

   return 0;

 }

 #endif /* !defined(SQLITE_OMIT_TRIGGER) */