Heikki Linnakangas <[email protected]> wrote:
> heap_insert() calls CheckForSerializableConflictIn(), which checks if
> there is a predicate lock on the whole relation, or on the page we're
> inserting to. It does not check for tuple-level locks, because there
> can't be any locks on a tuple that didn't exist before.
>
> AFAICS, the check for page lock is actually unnecessary. A page-level
> lock on a heap only occurs when tuple-level locks are promoted. It is
> just a coarser-grain representation of holding locks on all tuples on
> the page, *that exist already*. It is not a "gap" lock like the index
> locks are, it doesn't need to conflict with inserting new tuples on
the
> page. In fact, if heap_insert chose to insert the tuple on some other
> heap page, there would have been no conflict.
Absolutely correct. Patch attached.
-Kevin
*** a/src/backend/access/heap/heapam.c
--- b/src/backend/access/heap/heapam.c
***************
*** 1916,1926 **** heap_insert(Relation relation, HeapTuple tup, CommandId cid,
InvalidBuffer, options, bistate);
/*
! * We're about to do the actual insert -- check for conflict at the
! * relation or buffer level first, to avoid possibly having to roll back
! * work we've just done.
*/
! CheckForSerializableConflictIn(relation, NULL, buffer);
/* NO EREPORT(ERROR) from here till changes are logged */
START_CRIT_SECTION();
--- 1916,1929 ----
InvalidBuffer, options, bistate);
/*
! * We're about to do the actual insert -- check for conflict first, to
! * avoid possibly having to roll back work we've just done.
! *
! * NOTE: For a tuple insert, we only need to check for table locks,
since
! * predicate locking at the index level will cover ranges for anything
! * except a table scan. Therefore, only provide the relation.
*/
! CheckForSerializableConflictIn(relation, NULL, InvalidBuffer);
/* NO EREPORT(ERROR) from here till changes are logged */
START_CRIT_SECTION();
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