SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.433 2009/05/09 00:18:38 drh Exp $
*/
#include "sqliteInt.h"

/*
** Return the 'affinity' of the expression pExpr if any.
**
** If pExpr is a column, a reference to a column via an 'AS' alias,

}
void sqlite3TokenCopy(sqlite3 *db, Token *pTo, const Token *pFrom){
  if( pTo->dyn ) sqlite3DbFree(db, (char*)pTo->z);
  if( pFrom->z ){
    pTo->n = pFrom->n;
    pTo->z = (u8*)sqlite3DbStrNDup(db, (char*)pFrom->z, pFrom->n);
    pTo->dyn = 1;
    pTo->quoted = pFrom->quoted;
  }else{
    pTo->z = 0;
  }
}
ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p, int flags){
  ExprList *pNew;
  struct ExprList_item *pItem, *pOldItem;

/*
**
** 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 1.139 2009/05/09 00:18:38 drh Exp $
*/
#include "sqliteInt.h"

#ifndef SQLITE_OMIT_TRIGGER
/*
** Delete a linked list of TriggerStep structures.
*/

    sqlite3DbFree(db, pTmp);
  }
}

/*
** Given table pTab, return a list of all the triggers attached to 
** the table. The list is connected by Trigger.pNext pointers.
**
** All of the triggers on pTab that are in the same database as pTab
** are already attached to pTab->pTrigger.  But there might be additional
** triggers on pTab in the TEMP schema.  This routine prepends all
** TEMP triggers on pTab to the beginning of the pTab->pTrigger list
** and returns the combined list.
**
** To state it another way:  This routine returns a list of all triggers
** that fire off of pTab.  The list will include any TEMP triggers on
** pTab as well as the triggers lised in pTab->pTrigger.
*/
Trigger *sqlite3TriggerList(Parse *pParse, Table *pTab){
  Schema * const pTmpSchema = pParse->db->aDb[1].pSchema;
  Trigger *pList = 0;                  /* List of triggers to return */

  if( pTmpSchema!=pTab->pSchema ){
    HashElem *p;

  pTrigger->table = sqlite3DbStrDup(db, pTableName->a[0].zName);
  pTrigger->pSchema = db->aDb[iDb].pSchema;
  pTrigger->pTabSchema = pTab->pSchema;
  pTrigger->op = (u8)op;
  pTrigger->tr_tm = tr_tm==TK_BEFORE ? TRIGGER_BEFORE : TRIGGER_AFTER;
  pTrigger->pWhen = sqlite3ExprDup(db, pWhen, EXPRDUP_REDUCE);
  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);

  char *zName;                             /* Name of trigger */
  sqlite3 *db = pParse->db;                /* The database */
  DbFixer sFix;
  int iDb;                                 /* Database containing the trigger */

  pTrig = pParse->pNewTrigger;
  pParse->pNewTrigger = 0;
  if( NEVER(pParse->nErr) || !pTrig ) goto triggerfinish_cleanup;
  zName = pTrig->name;
  iDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
  pTrig->step_list = pStepList;
  while( pStepList ){
    pStepList->pTrig = pTrig;
    pStepList = pStepList->pNext;
  }

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);
  assert( 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

/*
** Remove a trigger from the hash tables of the sqlite* pointer.
*/
void sqlite3UnlinkAndDeleteTrigger(sqlite3 *db, int iDb, const char *zName){
  Hash *pHash = &(db->aDb[iDb].pSchema->trigHash);
  Trigger *pTrigger;
  pTrigger = sqlite3HashInsert(pHash, zName, sqlite3Strlen30(zName), 0);
  if( ALWAYS(pTrigger) ){
    if( pTrigger->pSchema==pTrigger->pTabSchema ){
      Table *pTab = tableOfTrigger(pTrigger);
      Trigger **pp;
      for(pp=&pTab->pTrigger; *pp!=pTrigger; pp=&((*pp)->pNext));
      *pp = (*pp)->pNext;
    }
    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==0 || NEVER(pEList==0) ) return 1;
  for(e=0; e<pEList->nExpr; e++){
    if( sqlite3IdListIndex(pIdList, pEList->a[e].zName)>=0 ) return 1;
  }
  return 0; 
}

/*

  int *pMask              /* OUT: Mask of TRIGGER_BEFORE|TRIGGER_AFTER */
){
  int mask = 0;
  Trigger *pList = sqlite3TriggerList(pParse, pTab);
  Trigger *p;
  assert( pList==0 || IsVirtual(pTab)==0 );
  for(p=pList; p; p=p->pNext){
    if( p->op==op && checkColumnOverlap(p->pColumns, pChanges) ){
      mask |= p->tr_tm;
    }
  }
  if( pMask ){
    *pMask = mask;
  }
  return (mask ? pList : 0);

  sqlite3VdbeAddOp2(v, OP_ContextPush, 0, 0);
  VdbeComment((v, "begin trigger %s", pStepList->pTrig->name));
  while( pTriggerStep ){
    sqlite3ExprCacheClear(pParse);
    orconf = (orconfin == OE_Default)?pTriggerStep->orconf:orconfin;
    pParse->trigStack->orconf = orconf;
    switch( pTriggerStep->op ){











      case TK_UPDATE: {
        SrcList *pSrc;
        pSrc = targetSrcList(pParse, pTriggerStep);
        sqlite3VdbeAddOp2(v, OP_ResetCount, 0, 0);
        sqlite3Update(pParse, pSrc,
                sqlite3ExprListDup(db, pTriggerStep->pExprList, 0), 
                sqlite3ExprDup(db, pTriggerStep->pWhere, 0), orconf);

        sqlite3VdbeAddOp2(v, OP_ResetCount, 0, 0);
        pSrc = targetSrcList(pParse, pTriggerStep);
        sqlite3DeleteFrom(pParse, pSrc, 
                          sqlite3ExprDup(db, pTriggerStep->pWhere, 0));
        sqlite3VdbeAddOp2(v, OP_ResetCount, 1, 0);
        break;
      }
      default: assert( pTriggerStep->op==TK_SELECT ); {
        Select *ss = sqlite3SelectDup(db, pTriggerStep->pSelect, 0);
        if( ss ){
          SelectDest dest;

          sqlite3SelectDestInit(&dest, SRT_Discard, 0);
          sqlite3Select(pParse, ss, &dest);
          sqlite3SelectDelete(db, ss);
        }
        break;
      }
    } 
    pTriggerStep = pTriggerStep->pNext;
  }
  sqlite3VdbeAddOp2(v, OP_ContextPop, 0, 0);
  VdbeComment((v, "end trigger %s", pStepList->pTrig->name));

  return 0;

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

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

  for(p=pTrigger; p; p=p->pNext){
    int fire_this = 0;

    /* Sanity checking:  The schema for the trigger and for the table are
    ** always defined.  The trigger must be in the same schema as the table
    ** or else it must be a TEMP trigger. */
    assert( p->pSchema!=0 );
    assert( p->pTabSchema!=0 );
    assert( p->pSchema==p->pTabSchema || p->pSchema==db->aDb[1].pSchema );

    /* Determine whether we should code this trigger */
    if( 
      p->op==op && 
      p->tr_tm==tr_tm && 

      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 */