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-rw-r--r--src/backend/access/nbtree/nbtinsert.c3
-rw-r--r--src/backend/access/table/tableam.c4
-rw-r--r--src/include/access/tableam.h4
3 files changed, 9 insertions, 2 deletions
diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index 55fe16bd4e1..b86c122763e 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -597,7 +597,8 @@ _bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
* not part of this chain because it had a different index
* entry.
*/
- if (table_index_fetch_tuple_check(heapRel, &itup->t_tid,
+ htid = itup->t_tid;
+ if (table_index_fetch_tuple_check(heapRel, &htid,
SnapshotSelf, NULL))
{
/* Normal case --- it's still live */
diff --git a/src/backend/access/table/tableam.c b/src/backend/access/table/tableam.c
index c814733b222..4b2bb29559a 100644
--- a/src/backend/access/table/tableam.c
+++ b/src/backend/access/table/tableam.c
@@ -196,6 +196,10 @@ table_beginscan_parallel(Relation relation, ParallelTableScanDesc parallel_scan)
* optimized, but is unlikely to matter from a performance POV. If there
* frequently are live index pointers also matching a unique index key, the
* CPU overhead of this routine is unlikely to matter.
+ *
+ * Note that *tid may be modified when we return true if the AM supports
+ * storing multiple row versions reachable via a single index entry (like
+ * heap's HOT).
*/
bool
table_index_fetch_tuple_check(Relation rel,
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index eb18739c365..b3d2a6dd315 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -989,7 +989,9 @@ table_index_fetch_end(struct IndexFetchTableData *scan)
/*
* Fetches, as part of an index scan, tuple at `tid` into `slot`, after doing
* a visibility test according to `snapshot`. If a tuple was found and passed
- * the visibility test, returns true, false otherwise.
+ * the visibility test, returns true, false otherwise. Note that *tid may be
+ * modified when we return true (see later remarks on multiple row versions
+ * reachable via a single index entry).
*
* *call_again needs to be false on the first call to table_index_fetch_tuple() for
* a tid. If there potentially is another tuple matching the tid, *call_again