Postgres pg_toast in autovacuum - which table?

Question

I have an autovacuum process running on pg_toast:

select query, from pg_stat_activity where query like '%autov%';
"autovacuum: VACUUM pg_toast.pg_toast_15404513 "

How do I find out what table/index/whatever this pg_toast pertains to? Or is the autovacuum working on something else?

Answer 1

Here's a shorter way:

select 15404513::regclass;

where 15404513 is pg_toast_ suffix.

Answer 2

I think you'll want something like:

select n.nspname, c.relname 
from pg_class c 
inner join pg_namespace n on c.relnamespace = n.oid
where reltoastrelid = (
    select oid
    from pg_class 
    where relname = 'pg_toast_15404513' 
    and relnamespace = (SELECT n2.oid FROM pg_namespace n2 WHERE n2.nspname = 'pg_toast') )

It'd be nice if Pg reported this in the vacuum command summary.