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Allow negative values for LIMIT and OFFSET. Add tests for negative LIMITs

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and OFFSETs.  Make the OFFSET work even if LIMIT is 0 or negative. (CVS 1052)

FossilOrigin-Name: e6a752bfef24f773973c151c6262ff331a9dc57a
This commit is contained in:
drh
2003-07-16 02:19:37 +00:00
parent d4f5ee2805
commit ef0cae500d
5 changed files with 80 additions and 32 deletions
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31
src/select.c
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@@ -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 1.141 2003/06/16 00:40:35 drh Exp $
** $Id: select.c,v 1.142 2003/07/16 02:19:38 drh Exp $
*/
#include "sqliteInt.h"
@@ -30,7 +30,7 @@ Select *sqliteSelectNew(
ExprList *pOrderBy, /* the ORDER BY clause */
int isDistinct, /* true if the DISTINCT keyword is present */
int nLimit, /* LIMIT value. -1 means not used */
int nOffset /* OFFSET value. -1 means not used */
int nOffset /* OFFSET value. 0 means no offset */
){
Select *pNew;
pNew = sqliteMalloc( sizeof(*pNew) );
@@ -2140,24 +2140,31 @@ int sqliteSelect(
generateColumnNames(pParse, pTabList, pEList);
}
/* Set the limiter
/* Set the limiter.
**
** The phrase "LIMIT 0" means all rows are shown, not zero rows.
** If the comparison is p->nLimit<=0 then "LIMIT 0" shows
** all rows. It is the same as no limit. If the comparision is
** p->nLimit<0 then "LIMIT 0" show no rows at all.
** "LIMIT -1" always shows all rows. There is some
** contraversy about what the correct behavior should be.
*/
if( p->nLimit<=0 ){
p->nLimit = -1;
p->nOffset = 0;
}else{
int iMem = pParse->nMem++;
sqliteVdbeAddOp(v, OP_Integer, -p->nLimit, 0);
sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
p->nLimit = iMem;
if( p->nOffset<=0 ){
p->nOffset = 0;
}else{
iMem = pParse->nMem++;
sqliteVdbeAddOp(v, OP_Integer, -p->nOffset, 0);
sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
p->nOffset = iMem;
}
}
if( p->nOffset<=0 ){
p->nOffset = 0;
}else{
int iMem = pParse->nMem++;
if( iMem==0 ) iMem = pParse->nMem++;
sqliteVdbeAddOp(v, OP_Integer, -p->nOffset, 0);
sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
p->nOffset = iMem;
}
/* Generate code for all sub-queries in the FROM clause