sl@0: /*
sl@0: ** 2008 August 16
sl@0: **
sl@0: ** The author disclaims copyright to this source code.  In place of
sl@0: ** a legal notice, here is a blessing:
sl@0: **
sl@0: **    May you do good and not evil.
sl@0: **    May you find forgiveness for yourself and forgive others.
sl@0: **    May you share freely, never taking more than you give.
sl@0: **
sl@0: *************************************************************************
sl@0: ** This file contains routines used for walking the parser tree for
sl@0: ** an SQL statement.
sl@0: **
sl@0: ** $Id: walker.c,v 1.1 2008/08/20 16:35:10 drh Exp $
sl@0: */
sl@0: #include "sqliteInt.h"
sl@0: #include <stdlib.h>
sl@0: #include <string.h>
sl@0: 
sl@0: 
sl@0: /*
sl@0: ** Walk an expression tree.  Invoke the callback once for each node
sl@0: ** of the expression, while decending.  (In other words, the callback
sl@0: ** is invoked before visiting children.)
sl@0: **
sl@0: ** The return value from the callback should be one of the WRC_*
sl@0: ** constants to specify how to proceed with the walk.
sl@0: **
sl@0: **    WRC_Continue      Continue descending down the tree.
sl@0: **
sl@0: **    WRC_Prune         Do not descend into child nodes.  But allow
sl@0: **                      the walk to continue with sibling nodes.
sl@0: **
sl@0: **    WRC_Abort         Do no more callbacks.  Unwind the stack and
sl@0: **                      return the top-level walk call.
sl@0: **
sl@0: ** The return value from this routine is WRC_Abort to abandon the tree walk
sl@0: ** and WRC_Continue to continue.
sl@0: */
sl@0: int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
sl@0:   int rc;
sl@0:   if( pExpr==0 ) return WRC_Continue;
sl@0:   rc = pWalker->xExprCallback(pWalker, pExpr);
sl@0:   if( rc==WRC_Continue ){
sl@0:     if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
sl@0:     if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort;
sl@0:     if( sqlite3WalkExprList(pWalker, pExpr->pList) ) return WRC_Abort;
sl@0:     if( sqlite3WalkSelect(pWalker, pExpr->pSelect) ){
sl@0:       return WRC_Abort;
sl@0:     }
sl@0:   }
sl@0:   return rc & WRC_Abort;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Call sqlite3WalkExpr() for every expression in list p or until
sl@0: ** an abort request is seen.
sl@0: */
sl@0: int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
sl@0:   int i, rc = WRC_Continue;
sl@0:   struct ExprList_item *pItem;
sl@0:   if( p ){
sl@0:     for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
sl@0:       if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
sl@0:     }
sl@0:   }
sl@0:   return rc & WRC_Continue;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Walk all expressions associated with SELECT statement p.  Do
sl@0: ** not invoke the SELECT callback on p, but do (of course) invoke
sl@0: ** any expr callbacks and SELECT callbacks that come from subqueries.
sl@0: ** Return WRC_Abort or WRC_Continue.
sl@0: */
sl@0: int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
sl@0:   if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
sl@0:   if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
sl@0:   if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
sl@0:   if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
sl@0:   if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
sl@0:   if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
sl@0:   if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort;
sl@0:   return WRC_Continue;
sl@0: }
sl@0: 
sl@0: /*
sl@0: ** Walk the parse trees associated with all subqueries in the
sl@0: ** FROM clause of SELECT statement p.  Do not invoke the select
sl@0: ** callback on p, but do invoke it on each FROM clause subquery
sl@0: ** and on any subqueries further down in the tree.  Return 
sl@0: ** WRC_Abort or WRC_Continue;
sl@0: */
sl@0: int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
sl@0:   SrcList *pSrc;
sl@0:   int i;
sl@0:   struct SrcList_item *pItem;
sl@0: 
sl@0:   pSrc = p->pSrc;
sl@0:   if( pSrc ){
sl@0:     for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
sl@0:       if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){
sl@0:         return WRC_Abort;
sl@0:       }
sl@0:     }
sl@0:   }
sl@0:   return WRC_Continue;
sl@0: } 
sl@0: 
sl@0: /*
sl@0: ** Call sqlite3WalkExpr() for every expression in Select statement p.
sl@0: ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
sl@0: ** on the compound select chain, p->pPrior.
sl@0: **
sl@0: ** Return WRC_Continue under normal conditions.  Return WRC_Abort if
sl@0: ** there is an abort request.
sl@0: **
sl@0: ** If the Walker does not have an xSelectCallback() then this routine
sl@0: ** is a no-op returning WRC_Continue.
sl@0: */
sl@0: int sqlite3WalkSelect(Walker *pWalker, Select *p){
sl@0:   int rc;
sl@0:   if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
sl@0:   rc = WRC_Continue;
sl@0:   while( p  ){
sl@0:     rc = pWalker->xSelectCallback(pWalker, p);
sl@0:     if( rc ) break;
sl@0:     if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort;
sl@0:     if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort;
sl@0:     p = p->pPrior;
sl@0:   }
sl@0:   return rc & WRC_Abort;
sl@0: }