diff options
| -rw-r--r-- | src/backend/executor/nodeUnique.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/src/backend/executor/nodeUnique.c b/src/backend/executor/nodeUnique.c index b71403de0b8..e571c2263f1 100644 --- a/src/backend/executor/nodeUnique.c +++ b/src/backend/executor/nodeUnique.c @@ -8,7 +8,7 @@ * * * 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 * 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 (;;) { @@ -66,10 +71,16 @@ ExecUnique(Unique *node) */ slot = ExecProcNode(outerPlan, (Plan *) node); 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; + } /* - * Always return the first tuple from the subplan. + * Always return the first/last tuple from the subplan. */ if (uniquestate->priorTuple == NULL) break; |