Re: Avoid Wraparound Failures

On 3/25/22 17:16, Loles wrote:
> Hi!
>
> Suppose the databases on my instance are near to have a wraparound failure.

Is this actually the case, or are you just afraid?

>
> (I think so, from what I see, but in the PostgreSQL log I haven't seen any
> warning about It yet).
>
> What do I have to do?
>
> vacuum freeze;

Kinda, but really... Heck No!!!

vacuum --freeze --jobs=`nproc` --dbname=your_db_name

That will VACUUM FREEZE every table in your database in multiple threads.

However, you only need to freeze tables getting near wraparound.
pg_class.relfrozenxid tells you which tables to worry about.

>
> better than,
>
> vacuum analyze;

VACUUM ANALYZE does a plain vacuum *plus* collects statistics for the query
analyzer.  Collecting query stats has nothing to do with vacuuming or
protecting against wraparound.

>
> Or both?
>
> If the autovacuum_freeze configuration parameters have defaults values,
> should I modify any first?
>

What version are you running?  Even the recently EOL versions protect from
wraparound (though it's a painful last-ditch process).

--
Angular momentum makes the world go 'round.