database/postgres
database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-05-01 01:04:50 +03:00
Code

Fix nodeUnique to behave correctly when reversing direction after reaching

Browse Source 
either end of subplan results.  This prevents misbehavior of cursors
on SELECT DISTINCT ... queries.  Per bug report 1-Feb-02.
This commit is contained in:
Tom Lane 2003-02-02 19:09:08 +00:00
parent d77c6396bb
commit e59750d684
1 changed files with 13 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/backend/executor/nodeUnique.c
View File

@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/nodeUnique.c,v 1.34 2002/06/20 20:29:28 momjian Exp $ * $Header: /cvsroot/pgsql/src/backend/executor/nodeUnique.c,v 1.34.2.1 2003/02/02 19:09:08 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -58,6 +58,11 @@ ExecUnique(Unique *node)
/* /*
* now loop, returning only non-duplicate tuples. We assume that the * now loop, returning only non-duplicate tuples. We assume that the
* tuples arrive in sorted order so we can detect duplicates easily. * tuples arrive in sorted order so we can detect duplicates easily.
*
* We return the first tuple from each group of duplicates (or the
* last tuple of each group, when moving backwards). At either end
* of the subplan, clear priorTuple so that we correctly return the
* first/last tuple when reversing direction.
*/ */
for (;;) for (;;)
{ {
@ -66,10 +71,16 @@ ExecUnique(Unique *node)
*/ */
slot = ExecProcNode(outerPlan, (Plan *) node); slot = ExecProcNode(outerPlan, (Plan *) node);
if (TupIsNull(slot)) if (TupIsNull(slot))
{
/* end of subplan; reset in case we change direction */
if (uniquestate->priorTuple != NULL)
heap_freetuple(uniquestate->priorTuple);
uniquestate->priorTuple = NULL;
return NULL; return NULL;
}
/* /*
* Always return the first tuple from the subplan. * Always return the first/last tuple from the subplan.
*/ */
if (uniquestate->priorTuple == NULL) if (uniquestate->priorTuple == NULL)
break; break;