Re: Something is wrong with wal_compression

On Fri, Jan 27, 2023, 18:58 Andres Freund <andres@anarazel.de> wrote:

> Hi,
>
> On 2023-01-27 16:15:08 +1300, Thomas Munro wrote:
> > It would be pg_current_xact_id() that would have to pay the cost of
> > the WAL flush, not pg_xact_status() itself, but yeah that's what the
> > patch does (with some optimisations).  I guess one question is whether
> > there are any other reasonable real world uses of
> > pg_current_xact_id(), other than the original goal[1].
>
> txid_current() is a lot older than pg_current_xact_id(), and they're
> backed by
> the same code afaict. 8.4 I think.
>
> Unfortunately txid_current() is used in plenty montiring setups IME.
>
> I don't think it's a good idea to make a function that was quite cheap for
> 15
> years, suddenly be several orders of magnitude more expensive...


As someone working on a monitoring tool that uses it (well, both), +1. We'd
have to rethink a few things if this becomes a performance concern.

Thanks,
Maciek