Re: pg_locks.relation question

On Wed, Apr 18, 2018 at 5:35 PM, Daniel Westermann <
daniel(dot)westermann(at)dbi-services(dot)com> wrote:

> Hi,
>
> session one:
>
> locks=# begin;
> BEGIN
> locks=# alter table test add column b text;
> ALTER TABLE
> locks=#
>
> Session 2 querying pg_locks for the PID from above:
>
> locks=# select locktype,relation::regclass,mode from pg_locks where pid =
> 2026 and locktype = 'relation';
> locktype | relation | mode
> ----------+----------+---------------------
> relation | test | AccessExclusiveLock
> relation | 17728 | AccessExclusiveLock
> relation | 17726 | ShareLock
> (3 rows)
>
> What are these 17728 and 17726 OIDs? Nothing else is happening except
> these two sessions.
>
>
Those are probably the OIDs of the toast table and the index on it. If you
commit the transaction running in Session 1 and then query pg_class for
those OIDs, you might see more details. Of course, I am just guessing
without looking into much detail.

Thanks,
Pavan

--
Pavan Deolasee http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services