Re: pg_autovacuum / pg_class

> Tomas Vondra wrote:
>> Hello,
>>
>> I have a simple question about auto-vacuuming. We are running a Postgres
>> 8.1 and I've noticed that some of the tables are not analyzed by the
>> pg_autovacuum daemon. That is - when I select the rows from pg_class,
>> all the important values (relpages, reltuples) are 0.
>>
>> I've noticed this in case of newly created tables (that is not older
>> than 1 month). My 'theory' is this - the table has to be analyzed by
>> hand at the beginning, otherwise the pg_autovacuum won't process it. Am
>> I right?
>
> Hum. Just by inserting tuples into those tables, autovacuum should "be
> able to see" them. Autovacuum won't touch, and indeed won't even
> consider, tables that are just created. But as soon as you insert a
> single tuple in them, it will start to consider vacuuming or analyzing
> them.
>
> If you insert a hundred thousand rows in a table, autovacuum most
> certainly should analyze it. If it's not, we'd really like to know why.

I feel very ashamed, as I've found the reason - the pg_autovacuum was
not running at all :( About month ago we've upgraded to PG 8.1, since
then the database was running without a restart but noone noticed the
warning about enabling stats_start_collector/stats_row_level.

I've noticed that only for the new tables (having 0 values in all
columns), as most of the other tables are not changing very frequently
(resp. have about the same number of inserts and deletes).

So now the pg_autovacuum is up and running, and I'll check how it works
tomorrow. But I guess this time it'll be fine.

Tomas