Re: Autovacuum on sys tables

Thanks Thomas for the response,

It means if I run VACUUM ANALYZE on pg_attribute or pg_class table, it is completely safe? Can you please also please confirm what is meant by "mid-level" vacuum?

Regards,

Inzamam Shafiq
Sr. DBA
________________________________
From: Thomas Boussekey <thomas(dot)boussekey(at)gmail(dot)com>
Sent: Sunday, December 18, 2022 4:01 PM
To: Inzamam Shafiq <inzamam(dot)shafiq(at)hotmail(dot)com>
Cc: pgsql-general(at)lists(dot)postgresql(dot)org <pgsql-general(at)lists(dot)postgresql(dot)org>
Subject: Re: Autovacuum on sys tables

Hello Inzamam,

Le sam. 17 déc. 2022 à 08:16, Inzamam Shafiq <inzamam(dot)shafiq(at)hotmail(dot)com<mailto:inzamam(dot)shafiq(at)hotmail(dot)com>> a écrit :
Dear Experts,

Hope you are doing well.

I have a question that autovacuum is running on sys tables like pg_class, pg_attribute, is it a normal thing? Further, what is dead tuples are not removed from Autovacuum, can we remove the dead tuples using FULL VACUUMM or pg_repack on sys tables?

pg_repack cannot run on system tables, it will FAIL with an explicit error message explaining the limitation.

Each time you perform DDL operations (CREATE, DROP, ALTER), rows are inserted/updated or deleted into the system tables : pg_class, pg_attribute ...
Autovacuum operations perform "low-level" operations, it can be interesting to perform "middle-level" vacuum with VACUUM ANALYZE... that is not blocking, but will be more a resource-consuming operation than autovacuum.

Performing VACUUM FULL operation will block access to these pillar tables of your database.
If your application/users can handle it, go ahead!
At work on this kind of operation, I set a statement_timeout, in order to properly stop the process if it is over a defined amount of time.

Hope this helps,
Thomas

Thank you.

Regards,

Inzamam Shafiq
Sr. DBA