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Message-ID: <b6e8f2e80809290533g2a7e09b1i110bb085ad75092e@mail.gmail.com>
Date: Mon, 29 Sep 2008 14:33:32 +0200
From: "Peter Kovacs" <maxottovonstirlitz@gmail.com>
To: "Tom Lane" <tgl@sss.pgh.pa.us>
Subject: Re: Do we need vacuuming when tables are regularly dropped?
Cc: pgsql-admin@postgresql.org
In-Reply-To: <9815.1222690583@sss.pgh.pa.us>
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References: <b6e8f2e80809290237p7685dbcfm9d5c886ba225b956@mail.gmail.com>
	<9815.1222690583@sss.pgh.pa.us>

On Mon, Sep 29, 2008 at 2:16 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> "Peter Kovacs" <maxottovonstirlitz@gmail.com> writes:
>> We have a number of automated performance tests (to test our own code)
>> involving PostgreSQL. Test cases are supposed to drop and recreate
>> tables each time they run.
>
>> The problem is that some of the tests show a linear performance
>> degradation overtime. (We have data for three months back in the
>> past.) We have established that some element(s) of our test
>> environment must be the culprit for the degradation. As rebooting the
>> test machine didn't revert speeds to baselines recorded three months
>> ago, we have turned our attention to the database as the only element
>> of the environment which is persistent across reboots. Recreating the
>> entire PGSQL cluster did cause speeds to revert to baselines.
>
> What it sounds like to me is that you're not vacuuming the system
> catalogs, which are getting bloated with dead rows about all those
> dropped tables.

Wow, great!

It is not immediately clear from the documentation, but the VACUUM
command also deals with the system catalogs as well, correct?

Thanks a lot!
Peter

>
>                        regards, tom lane
>