Re: BUG #13750: Autovacuum slows down with large numbers of tables. More workers makes it slower.

On 11/06/2015 04:46 PM, David Gould wrote:
>> 3. Do we want to backpatch?  Changes in behavior aren't acceptable on
>> > existing branches, because it might destabilize autovacuum behavior
>> > that's been carefully tuned in existing systems.  So if we want
>> > something to backpatch, ideally it shouldn't change the ordering in
>> > which tables are vacuumed, and instead arrive at the same results
>> > faster.  (I don't care about this restriction myself, but others do and
>> > strongly so.)
> The current order of autovacuum operations is the physical order of the
> rows in pg_class plus some jitter depending on which worker is able to grab
> a table first. It seems unlikely anything could depend on this
> particular order.

I don't know anyone who depends on the ordering of autovacuum, because
nobody knows what it is.  It's not exactly documented.

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com