Re: [PATCH] pg_dump: lock tables in batches

On Wed, Dec 7, 2022 at 12:09 PM Aleksander Alekseev <
aleksander(at)timescale(dot)com> wrote:
>
> Hi hackers,
>
> A colleague of mine reported a slight inconvenience with pg_dump.
>
> He is dumping the data from a remote server. There are several
> thousands of tables in the database. Making a dump locally and/or
> using pg_basebackup and/or logical replication is not an option. So
> what pg_dump currently does is sending LOCK TABLE queries one after
> another. Every query needs an extra round trip. So if we have let's
> say 2000 tables and every round trip takes 100 ms then ~3.5 minutes
> are spent in the not most useful way.
>
> What he proposes is taking the locks in batches. I.e. instead of:
>
> LOCK TABLE foo IN ACCESS SHARE MODE;
> LOCK TABLE bar IN ACCESS SHARE MODE;
>
> do:
>
> LOCK TABLE foo, bar, ... IN ACCESS SHARE MODE;
>
> The proposed patch makes this change. It's pretty straightforward and
> as a side effect saves a bit of network traffic too.
>

+1 for that change. It will improve the dump for databases with thousands
of relations.

The code LGTM and it passes in all tests and compiles without any warning.

Regards,

--
Fabrízio de Royes Mello