Fix nasty bug in nodeIndexscan.c's detection of duplicate tuples during

a multiple (OR'ed) indexscan.  It was checking for duplicate
tuple->t_data->t_ctid, when what it should be checking is tuple->t_self.
The trouble situation occurs when a live tuple has t_ctid not pointing to
itself, which can happen if an attempted UPDATE was rolled back.  After a
VACUUM, an unrelated tuple could be installed where the failed update tuple
was, leading to one live tuple's t_ctid pointing to an unrelated tuple.
If one of these tuples is fetched by an earlier OR'ed indexscan and the other
by a later indexscan, nodeIndexscan.c would incorrectly ignore the second
tuple.  The bug exists in all 7.4.* and 8.0.* versions, but not in earlier
or later branches because this code was only used in those releases.  Per
trouble report from Rafael Martinez Guerrero.

diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index 80ff0369ba144044f2b844603784685a398bd76d..b3909a2f9e4fe17b3c910399bdeca1a27901cb1f 100644 (file)
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -249,7 +249,7 @@ IndexNext(IndexScanState *node)
 
                                        entry = (DupHashTabEntry *)
                                                hash_search(node->iss_DupHash,
-                                                                       &tuple->t_data->t_ctid,
+                                                                       &tuple->t_self,
                                                                        HASH_ENTER,
                                                                        &found);
                                        if (entry == NULL ||