I would recommend (if at all possible) to partition the table and drop
the old partitions when not needed. This will guarantee the space
free-up without VACUUM overhead. Deletes will kill you at some point
and you dont want too much of the VACUUM IO overhead impacting your
performance.
On Mon, Nov 2, 2009 at 4:50 AM, Peter Meszaros <pme@prolan.hu> wrote:
> Thank you all for the fast responses!
>
> I changed the delete's schedule from daily to hourly and I will let you
> know the result. This seems to be the most promising step.
>
> The next one is tuning 'max_fsm_pages'.
> Increasing max_fsm_pages can be also helpful, but I've read that
> 'vacuum verbose ...' will issue warnings if max_fsm_pages is too small.
> I've never seen such messag, this command is either run and finish or
> goes to an endless loop as it was written in my initial e-mail.
>
>
> On Thu, Oct 29, 2009 at 10:59:48AM -0600, Scott Marlowe wrote:
>> On Thu, Oct 29, 2009 at 8:44 AM, Peter Meszaros <pme@prolan.hu> wrote:
>> > Hi All,
>> >
>> > I use postgresql 8.3.7 as a huge queue. There is a very simple table
>> > with six columns and two indices, and about 6 million records are
>> > written into it in every day continously commited every 10 seconds from
>> > 8 clients. The table stores approximately 120 million records, because a
>> > cron job daily deletes those ones are older than 20 day. Autovacuum is
>> > on and every settings is the factory default except some unrelated ones
>> > (listen address, authorization). But my database is growing,
>> > characteristically ~600MByte/day, but sometimes much slower (eg. 10MB,
>> > or even 0!!!).
>>
>> Sounds like you're blowing out your free space map. Things to try:
>>
>> 1: delete your rows in smaller batches. Like every hour delete
>> everything over 20 days so you don't delete them all at once one time
>> a day.
>> 2: crank up max fsm pages large enough to hold all the dead tuples.
>> 3: lower the autovacuum cost delay
>> 4: get faster hard drives so that vacuum can keep up without causing
>> your system to slow to a crawl while vacuum is running.
>
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> Mon Nov 2 13:20:39 CET 2009
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