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| author | Peter Geoghegan <pg@bowt.ie> | 2020-06-25 10:55:28 -0700 |
|---|---|---|
| committer | Peter Geoghegan <pg@bowt.ie> | 2020-06-25 10:55:28 -0700 |
| commit | 10f1ab2cb8bea3c6741a78f6dc19a5c91c0a34e1 (patch) | |
| tree | 37a1a8de2bd0d98a2a76341fb5d8a6426d757f0f /src | |
| parent | 463b808e757928f053490dd397af77a80b4e7baa (diff) | |
| download | postgresql-10f1ab2cb8bea3c6741a78f6dc19a5c91c0a34e1.tar.gz postgresql-10f1ab2cb8bea3c6741a78f6dc19a5c91c0a34e1.zip | |
Fix misuse of table_index_fetch_tuple_check().
Commit 0d861bbb, which added deduplication to nbtree, had
_bt_check_unique() pass a TID to table_index_fetch_tuple_check() that
isn't safe to mutate. table_index_fetch_tuple_check()'s tid argument is
modified when the TID in question is not the latest visible tuple in a
hot chain, though this wasn't documented.
To fix, go back to using a local copy of the TID in _bt_check_unique(),
and update comments above table_index_fetch_tuple_check().
Backpatch: 13-, where B-Tree deduplication was introduced.
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/nbtree/nbtinsert.c | 3 | ||||
| -rw-r--r-- | src/backend/access/table/tableam.c | 4 | ||||
| -rw-r--r-- | src/include/access/tableam.h | 4 |
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 |