Disable the result-set alias cache when on conditional code branches.

Ticket #3461.  The column cache and result set alias cache mechanisms are
prone to this kind of error and need to be refactored.  This check-in should
be considered a temporary fix in advance of a more general redesign of the
whole mechanism. (CVS 5841)

FossilOrigin-Name: 1fa3bbd8220ce073e91935ea362b6f5d5d6d2859

1 files changed, 14 insertions, 8 deletions

diff --git a/src/expr.c b/src/expr.c
index 52f7cdb7d..10393e0a5 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -12,7 +12,7 @@
 ** This file contains routines used for analyzing expressions and
 ** for generating VDBE code that evaluates expressions in SQLite.
 **
-** $Id: expr.c,v 1.399 2008/10/11 16:47:36 drh Exp $
+** $Id: expr.c,v 1.400 2008/10/25 15:03:21 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
@@ -1718,7 +1718,7 @@ void sqlite3ExprHardCopy(Parse *pParse, int iReg, int nReg){
 ** of the iAlias-th alias is stored.  If zero, that means that the
 ** alias has not yet been computed.
 */
-static int codeAlias(Parse *pParse, int iAlias, Expr *pExpr){
+static int codeAlias(Parse *pParse, int iAlias, Expr *pExpr, int target){
   sqlite3 *db = pParse->db;
   int iReg;
   if( pParse->aAlias==0 ){
@@ -1729,9 +1729,13 @@ static int codeAlias(Parse *pParse, int iAlias, Expr *pExpr){
   assert( iAlias>0 && iAlias<=pParse->nAlias );
   iReg = pParse->aAlias[iAlias-1];
   if( iReg==0 ){
-    iReg = ++pParse->nMem;
-    sqlite3ExprCode(pParse, pExpr, iReg);
-    pParse->aAlias[iAlias-1] = iReg;
+    if( pParse->disableColCache ){
+      iReg = sqlite3ExprCodeTarget(pParse, pExpr, target);
+    }else{
+      iReg = ++pParse->nMem;
+      sqlite3ExprCode(pParse, pExpr, iReg);
+      pParse->aAlias[iAlias-1] = iReg;
+    }
   }
   return iReg;
 }
@@ -1840,7 +1844,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
       break;
     }
     case TK_AS: {
-      inReg = codeAlias(pParse, pExpr->iTable, pExpr->pLeft);
+      inReg = codeAlias(pParse, pExpr->iTable, pExpr->pLeft, target);
       break;
     }
 #ifndef SQLITE_OMIT_CAST
@@ -2500,9 +2504,11 @@ int sqlite3ExprCodeExprList(
   n = pList->nExpr;
   for(pItem=pList->a, i=0; i<n; i++, pItem++){
     if( pItem->iAlias ){
-      int iReg = codeAlias(pParse, pItem->iAlias, pItem->pExpr);
+      int iReg = codeAlias(pParse, pItem->iAlias, pItem->pExpr, target+i);
       Vdbe *v = sqlite3GetVdbe(pParse);
-      sqlite3VdbeAddOp2(v, OP_SCopy, iReg, target+i);
+      if( iReg!=target+i ){
+        sqlite3VdbeAddOp2(v, OP_SCopy, iReg, target+i);
+      }
     }else{
       sqlite3ExprCode(pParse, pItem->pExpr, target+i);
     }