Fix for ticket #31: Do not attempt the flattening optimization if the

subselect does not contain a FROM clause.  Handle the special case where
a WHERE clause is constant. (CVS 548)

FossilOrigin-Name: 24e4cf73d22bb41d26bf3c833f1854a9c90923e8

2 files changed, 13 insertions, 4 deletions

diff --git a/src/select.c b/src/select.c
index 0f2fc609a..530a7a3dd 100644
--- a/src/select.c
+++ b/src/select.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle SELECT statements in SQLite.
 **
-** $Id: select.c,v 1.79 2002/04/23 17:10:18 drh Exp $
+** $Id: select.c,v 1.80 2002/04/30 19:20:29 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -918,6 +918,8 @@ substExprList(ExprList *pList, int iTable, ExprList *pEList, int iSub){
 **   (6)  The subquery does not use aggregates or the outer query is not
 **        DISTINCT.
 **
+**   (7)  The subquery has a FROM clause.
+**
 ** In this routine, the "p" parameter is a pointer to the outer query.
 ** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
 ** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
@@ -947,7 +949,7 @@ int flattenSubquery(Select *p, int iFrom, int isAgg, int subqueryIsAgg){
   if( subqueryIsAgg && pSrc->nId>1 ) return 0;
   pSubSrc = pSub->pSrc;
   assert( pSubSrc );
-  if( pSubSrc->nId>1 ) return 0;
+  if( pSubSrc->nId!=1 ) return 0;
   if( pSub->isDistinct && pSrc->nId>1 ) return 0;
   if( pSub->isDistinct && isAgg ) return 0;
   if( p->isDistinct && subqueryIsAgg ) return 0;
diff --git a/src/where.c b/src/where.c
index 0d685137a..42b6bac4d 100644
--- a/src/where.c
+++ b/src/where.c
@@ -13,7 +13,7 @@
 ** the WHERE clause of SQL statements.  Also found here are subroutines
 ** to generate VDBE code to evaluate expressions.
 **
-** $Id: where.c,v 1.40 2002/04/02 13:26:11 drh Exp $
+** $Id: where.c,v 1.41 2002/04/30 19:20:29 drh Exp $
 */
 #include "sqliteInt.h"
 
@@ -193,6 +193,14 @@ WhereInfo *sqliteWhereBegin(
   pWInfo->pTabList = pTabList;
   pWInfo->base = base;
   pWInfo->peakNTab = pWInfo->savedNTab = pParse->nTab;
+  pWInfo->iBreak = sqliteVdbeMakeLabel(v);
+
+  /* Special case: a WHERE clause that is constant.  Evaluate the
+  ** expression and either jump over all of the code or fall thru.
+  */
+  if( pWhere && sqliteExprIsConstant(pWhere) ){
+    sqliteExprIfFalse(pParse, pWhere, pWInfo->iBreak);
+  }
 
   /* Split the WHERE clause into as many as 32 separate subexpressions
   ** where each subexpression is separated by an AND operator.  Any additional
@@ -422,7 +430,6 @@ WhereInfo *sqliteWhereBegin(
   /* Generate the code to do the search
   */
   loopMask = 0;
-  pWInfo->iBreak = sqliteVdbeMakeLabel(v);
   for(i=0; i<pTabList->nId; i++){
     int j, k;
     int idx = aOrder[i];