Re: pgsql: Implement pg_wal_replay_wait() stored procedure - Mailing list pgsql-hackers

From Alexander Korotkov
Subject Re: pgsql: Implement pg_wal_replay_wait() stored procedure
Date
Msg-id CAPpHfdu72Jb=JOVr4Mz3EiAqK30UFuCsQuFMiCyXNzECd1nYdQ@mail.gmail.com
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In response to Re: pgsql: Implement pg_wal_replay_wait() stored procedure  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
List pgsql-hackers
On Mon, Nov 4, 2024 at 4:19 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> On 2024-Nov-04, Alexander Korotkov wrote:
>
> > On Mon, Nov 4, 2024 at 8:04 AM Michael Paquier <michael@paquier.xyz> wrote:
>
> > > Using output parameters in a procedure is something I did not recall.
> > > Based on your point about not using a function due your argument based
> > > on the snapshots, let's just use that and forget about the status
> > > function entirely (please?).
> >
> > Please, check [1].  Usage of output parameters is a bit awkward too,
> > because you need to pass some value in there.  And more importantly,
> > usage of output parameters also causes snapshot problem, as it causes
> > another snapshot to be held.
>
> I wonder if it would be better to go back to the original idea of using
> special DDL syntax rather than a procedure.  It seems we've been piling
> up hacks to get around the behavior of procedures, and we seem to have
> grown one more to handle repeatable read transactions.
>
> It's looking to me like there's just too much cruft in the quest to
> avoid having to reach consensus on new syntax.  This might be a mistake.
> Is it possible to backtrack on that decision?

Before committing pg_wal_replay_wait() I was under impression that
stored procedure would require the same amount of efforts than utility
statement to make backend "snapshot-less".  However, it appears that
if we have implicit REPEATABLE READ transaction, stored procedure
needs more efforts.  That makes the whole decision, at least,
questionable.

------
Regards,
Alexander Korotkov
Supabase



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