| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | vignesh C <vignesh21(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Peter Smith <smithpb2250(at)gmail(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: pg_upgrade and logical replication |
| Date: | 2024-07-21 02:03:07 |
| Message-ID: | ZpxsWx5jwlMCBZfn@nathan |
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| Lists: | pgsql-hackers |
On Fri, Jul 19, 2024 at 03:44:22PM -0500, Nathan Bossart wrote:
> I've been looking into optimizing pg_upgrade's once-in-each-database steps
> [0], and I noticed that we are opening a connection to every database in
> the cluster and running a query like
>
> SELECT count(*) FROM pg_catalog.pg_subscription WHERE subdbid = %d;
>
> Then, later on, we combine all of these values in
> count_old_cluster_subscriptions() to verify that max_replication_slots is
> set high enough. AFAICT these per-database subscription counts aren't used
> for anything else.
>
> This is an extremely expensive way to perform that check, and so I'm
> wondering why we don't just do
>
> SELECT count(*) FROM pg_catalog.pg_subscription;
>
> once in count_old_cluster_subscriptions().
Like so...
--
nathan
| Attachment | Content-Type | Size |
|---|---|---|
| v1-0001-pg_upgrade-retrieve-subscription-count-more-effic.patch | text/plain | 5.4 KB |
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