/*

**

** 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 1.128 2008/07/28 19:34:54 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);

          sqlite3SelectResolve(pParse, ss, 0);

          sqlite3Select(pParse, ss, &dest, 0, 0, 0);

          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 || sqlite3ExprResolveNames(&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) */