Hi, Le lun. 19 déc. 2022 à 07:12, Inzamam Shafiq <inzamam.sha...@hotmail.com> a écrit :
> 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? > To clarify my last message, VACUUM ANALYZE is a trade-off between autovacuum, that can be considered as a lazy non-blocking operation, and VACUUM FULL (eager & blocking one). The `mid-level` in my previous mail was used to pinpoint an intermediate blacking & resource consumption situation. VACUUM ANALYZE will: - remove dead tuples definition - refresh statistics (can improve execution plans for queries) Have a look at this website, it explains that better than me ;) : https://www.interdb.jp/pg/pgsql06.html > > Regards, > > *Inzamam Shafiq* > *Sr. DBA* > ------------------------------ > *From:* Thomas Boussekey <thomas.bousse...@gmail.com> > *Sent:* Sunday, December 18, 2022 4:01 PM > *To:* Inzamam Shafiq <inzamam.sha...@hotmail.com> > *Cc:* pgsql-general@lists.postgresql.org < > pgsql-general@lists.postgresql.org> > *Subject:* Re: Autovacuum on sys tables > > Hello Inzamam, > > Le sam. 17 déc. 2022 à 08:16, Inzamam Shafiq <inzamam.sha...@hotmail.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* > >
