Fix bugs in SSI tuple locking.

1. In heap_hot_search_buffer(), the PredicateLockTuple() call is passed
wrong offset number. heapTuple->t_self is set to the tid of the first
tuple in the chain that's visited, not the one actually being read.

2. CheckForSerializableConflictIn() uses the tuple's t_ctid field
instead of t_self to check for exiting predicate locks on the tuple. If
the tuple was updated, but the updater rolled back, t_ctid points to the
aborted dead tuple.

Reported by Hannu Krosing. Backpatch to 9.1.

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index ead3d690aea7db7579f488c09a53cadd75c9df4f..a21f31b4095dff1e3672e0416e3cd3f05800e216 100644 (file)
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -1688,6 +1688,8 @@ heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer,
    at_chain_start = first_call;
    skip = !first_call;
 
+   heapTuple->t_self = *tid;
+
    /* Scan through possible multiple members of HOT-chain */
    for (;;)
    {
@@ -1717,7 +1719,7 @@ heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer,
        heapTuple->t_data = (HeapTupleHeader) PageGetItem(dp, lp);
        heapTuple->t_len = ItemIdGetLength(lp);
        heapTuple->t_tableOid = RelationGetRelid(relation);
-       heapTuple->t_self = *tid;
+       ItemPointerSetOffsetNumber(&heapTuple->t_self, offnum);
 
        /*
         * Shouldn't see a HEAP_ONLY tuple at chain start.

diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c
index c0d369a431aaedecd288313ed61dde56bb64ba1c..a8a0e987a87eefd95a46e8fb3d351111f2494e21 100644 (file)
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -4279,8 +4279,8 @@ CheckForSerializableConflictIn(Relation relation, HeapTuple tuple,
        SET_PREDICATELOCKTARGETTAG_TUPLE(targettag,
                                         relation->rd_node.dbNode,
                                         relation->rd_id,
-                        ItemPointerGetBlockNumber(&(tuple->t_data->t_ctid)),
-                       ItemPointerGetOffsetNumber(&(tuple->t_data->t_ctid)));
+                                 ItemPointerGetBlockNumber(&(tuple->t_self)),
+                               ItemPointerGetOffsetNumber(&(tuple->t_self)));
        CheckTargetForConflictsIn(&targettag);
    }