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Fix a bug in the reverse scan logic that comes up when the table being

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scanned is empty.  Add additional tests for the reverse scan. (CVS 797)

FossilOrigin-Name: 0051c87d5e8d07fae09da2eb7b0d8cbd1bbd3c8e
This commit is contained in:
drh
2002-12-04 22:29:28 +00:00
parent dd4852c3d1
commit 1a844c380b
5 changed files with 125 additions and 17 deletions
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7
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.74 2002/12/04 13:40:26 drh Exp $
** $Id: btree.c,v 1.75 2002/12/04 22:29:28 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@@ -1495,7 +1495,8 @@ int sqliteBtreeLast(BtCursor *pCur, int *pRes){
** this value is as follows:
**
** *pRes<0 The cursor is left pointing at an entry that
** is smaller than pKey.
** is smaller than pKey or if the table is empty
** and the cursor is therefore left point to nothing.
**
** *pRes==0 The cursor is left pointing at an entry that
** exactly matches pKey.
@@ -1513,7 +1514,7 @@ int sqliteBtreeMoveto(BtCursor *pCur, const void *pKey, int nKey, int *pRes){
int lwr, upr;
Pgno chldPg;
MemPage *pPage = pCur->pPage;
int c = -1;
int c = -1; /* pRes return if table is empty must be -1 */
lwr = 0;
upr = pPage->nCell-1;
while( lwr<=upr ){

16
src/vdbe.c
View File

@@ -36,7 +36,7 @@
** in this file for details. If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.186 2002/12/04 20:01:06 drh Exp $
** $Id: vdbe.c,v 1.187 2002/12/04 22:29:29 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
@@ -3394,9 +3394,17 @@ case OP_MoveTo: {
if( res && pOp->p2>0 ){
pc = pOp->p2 - 1;
}
}else if( oc==OP_MoveLt && res>=0 ){
sqliteBtreePrevious(pC->pCursor, &res);
pC->recnoIsValid = 0;
}else if( oc==OP_MoveLt ){
if( res>=0 ){
sqliteBtreePrevious(pC->pCursor, &res);
pC->recnoIsValid = 0;
}else{
/* res might be negative because the table is empty. Check to
** see if this is the case.
*/
int keysize;
res = sqliteBtreeKeySize(pC->pCursor,&keysize)!=0 || keysize==0;
}
if( res && pOp->p2>0 ){
pc = pOp->p2 - 1;
}