/*
** 2008 August 16
**
** 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.
**
*************************************************************************
** This file contains routines used for walking the parser tree for
** an SQL statement.
**
** $Id: walker.c,v 1.7 2009/06/15 23:15:59 drh Exp $
*/
#include "sqliteInt.h"
#include <stdlib.h>
#include <string.h>
/*
** Walk an expression tree. Invoke the callback once for each node
** of the expression, while decending. (In other words, the callback
** is invoked before visiting children.)
**
** The return value from the callback should be one of the WRC_*
** constants to specify how to proceed with the walk.
**
** WRC_Continue Continue descending down the tree.
**
** WRC_Prune Do not descend into child nodes. But allow
** the walk to continue with sibling nodes.
**
** WRC_Abort Do no more callbacks. Unwind the stack and
** return the top-level walk call.
**
** The return value from this routine is WRC_Abort to abandon the tree walk
** and WRC_Continue to continue.
*/
int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
int rc;
if( pExpr==0 ) return WRC_Continue;
testcase( ExprHasProperty(pExpr, EP_TokenOnly) );
testcase( ExprHasProperty(pExpr, EP_Reduced) );
rc = pWalker->xExprCallback(pWalker, pExpr);
if( rc==WRC_Continue
&& !ExprHasAnyProperty(pExpr,EP_TokenOnly) ){
if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort;
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort;
}else{
if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
}
}
return rc & WRC_Abort;
}
/*
** Call sqlite3WalkExpr() for every expression in list p or until
** an abort request is seen.
*/
int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
int i;
struct ExprList_item *pItem;
if( p ){
for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
}
}
return WRC_Continue;
}
/*
** Walk all expressions associated with SELECT statement p. Do
** not invoke the SELECT callback on p, but do (of course) invoke
** any expr callbacks and SELECT callbacks that come from subqueries.
** Return WRC_Abort or WRC_Continue.
*/
int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort;
return WRC_Continue;
}
/*
** Walk the parse trees associated with all subqueries in the
** FROM clause of SELECT statement p. Do not invoke the select
** callback on p, but do invoke it on each FROM clause subquery
** and on any subqueries further down in the tree. Return
** WRC_Abort or WRC_Continue;
*/
int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
SrcList *pSrc;
int i;
struct SrcList_item *pItem;
pSrc = p->pSrc;
if( ALWAYS(pSrc) ){
for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){
return WRC_Abort;
}
}
}
return WRC_Continue;
}
/*
** Call sqlite3WalkExpr() for every expression in Select statement p.
** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
** on the compound select chain, p->pPrior.
**
** Return WRC_Continue under normal conditions. Return WRC_Abort if
** there is an abort request.
**
** If the Walker does not have an xSelectCallback() then this routine
** is a no-op returning WRC_Continue.
*/
int sqlite3WalkSelect(Walker *pWalker, Select *p){
int rc;
if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
rc = WRC_Continue;
while( p ){
rc = pWalker->xSelectCallback(pWalker, p);
if( rc ) break;
if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort;
if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort;
p = p->pPrior;
}
return rc & WRC_Abort;
}