persistentstorage/sqlite3api/SQLite/walker.c
author Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
Fri, 22 Jan 2010 11:06:30 +0200
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permissions -rw-r--r--
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/*
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** 2008 August 16
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**
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** The author disclaims copyright to this source code.  In place of
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** a legal notice, here is a blessing:
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**
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**    May you do good and not evil.
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**    May you find forgiveness for yourself and forgive others.
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**    May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file contains routines used for walking the parser tree for
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** an SQL statement.
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**
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** $Id: walker.c,v 1.1 2008/08/20 16:35:10 drh Exp $
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*/
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#include "sqliteInt.h"
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#include <stdlib.h>
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#include <string.h>
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/*
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** Walk an expression tree.  Invoke the callback once for each node
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** of the expression, while decending.  (In other words, the callback
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** is invoked before visiting children.)
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**
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** The return value from the callback should be one of the WRC_*
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** constants to specify how to proceed with the walk.
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**
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**    WRC_Continue      Continue descending down the tree.
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**
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**    WRC_Prune         Do not descend into child nodes.  But allow
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**                      the walk to continue with sibling nodes.
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**
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**    WRC_Abort         Do no more callbacks.  Unwind the stack and
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**                      return the top-level walk call.
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**
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** The return value from this routine is WRC_Abort to abandon the tree walk
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** and WRC_Continue to continue.
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*/
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int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
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  int rc;
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  if( pExpr==0 ) return WRC_Continue;
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  rc = pWalker->xExprCallback(pWalker, pExpr);
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  if( rc==WRC_Continue ){
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    if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
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    if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort;
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    if( sqlite3WalkExprList(pWalker, pExpr->pList) ) return WRC_Abort;
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    if( sqlite3WalkSelect(pWalker, pExpr->pSelect) ){
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      return WRC_Abort;
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    }
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  }
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  return rc & WRC_Abort;
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}
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/*
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** Call sqlite3WalkExpr() for every expression in list p or until
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** an abort request is seen.
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*/
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int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
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  int i, rc = WRC_Continue;
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  struct ExprList_item *pItem;
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  if( p ){
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    for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
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      if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
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    }
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  }
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  return rc & WRC_Continue;
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}
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/*
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** Walk all expressions associated with SELECT statement p.  Do
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** not invoke the SELECT callback on p, but do (of course) invoke
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** any expr callbacks and SELECT callbacks that come from subqueries.
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** Return WRC_Abort or WRC_Continue.
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*/
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int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
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  if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
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  if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
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  if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
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  if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
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  if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
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  if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
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  if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort;
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  return WRC_Continue;
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}
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/*
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** Walk the parse trees associated with all subqueries in the
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** FROM clause of SELECT statement p.  Do not invoke the select
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** callback on p, but do invoke it on each FROM clause subquery
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** and on any subqueries further down in the tree.  Return 
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** WRC_Abort or WRC_Continue;
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*/
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int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
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  SrcList *pSrc;
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  int i;
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  struct SrcList_item *pItem;
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  pSrc = p->pSrc;
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  if( pSrc ){
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    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
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      if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){
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        return WRC_Abort;
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      }
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    }
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  }
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  return WRC_Continue;
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} 
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/*
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** Call sqlite3WalkExpr() for every expression in Select statement p.
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** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
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** on the compound select chain, p->pPrior.
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**
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** Return WRC_Continue under normal conditions.  Return WRC_Abort if
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** there is an abort request.
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**
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** If the Walker does not have an xSelectCallback() then this routine
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** is a no-op returning WRC_Continue.
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*/
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int sqlite3WalkSelect(Walker *pWalker, Select *p){
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  int rc;
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  if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
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  rc = WRC_Continue;
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  while( p  ){
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    rc = pWalker->xSelectCallback(pWalker, p);
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    if( rc ) break;
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    if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort;
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    if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort;
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    p = p->pPrior;
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  }
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  return rc & WRC_Abort;
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}