Re: Catalog_xmin is not advanced when a logical slot is lost

On Mon, Nov 21, 2022 at 8:05 AM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
wrote:

> On 2022-Nov-21, sirisha chamarthi wrote:
>
> > > > I am a fan of stricter, all-assumption-covering conditions. In case
> we
> > > > don't want to check restart_lsn, an Assert might be useful to
> validate
> > > > our assumption.
> > >
> > > Agreed. I'll throw in an assert.
> >
> > Changed this in the patch to throw an assert.
>
> Thank you. I had pushed mine for CirrusCI to test, and it failed the
> assert I added in slot.c:
> https://cirrus-ci.com/build/4786354503548928
> Not yet sure why, looking into it.
>

Can this be because restart_lsn is not set to InvalidXLogRecPtr for the
physical slots? My repro is as follows:

select pg_create_physical_replication_slot('s5');
// Load some data to invalidate slot
postgres(at)pgvm:~$ /usr/local/pgsql/bin/pg_receivewal -S s5 -D .
pg_receivewal: error: unexpected termination of replication stream: ERROR:
requested WAL segment 0000000100000000000000EB has already been removed
pg_receivewal: disconnected; waiting 5 seconds to try again
pg_receivewal: error: unexpected termination of replication stream: ERROR:
requested WAL segment 0000000100000000000000EB has already been removed
pg_receivewal: disconnected; waiting 5 seconds to try again
^Cpostgres(at)pgvm:~$ /usr/local/pgsql/bin/psql
psql (16devel)
Type "help" for help.

postgres=# select * from pg_replication_slots;
slot_name | plugin | slot_type | datoid | database | temporary |
active | active_pid | xmin | catalog_xmin | restart_lsn |
confirmed_flush_lsn | wal_status | safe_wal_size | two_phase
-----------+---------------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------+------------+---------------+-----------
s3 | test_decoding | logical | 5 | postgres | f | f
| | | 769 | | 0/A992E7D0
| lost | | f
s5 | | physical | | | f | f
| | | | 0/EB000000 |
| lost | | f

>
>
> --
> Álvaro Herrera PostgreSQL Developer —
> https://www.EnterpriseDB.com/
>