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Re: postgresql meltdown on

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Neil Conway" <neilc(at)samurai(dot)com>
Cc: sean(at)chittenden(dot)org, logan(at)datacurrent(dot)com,pgsql-performance(at)postgresql(dot)org
Subject: Re: postgresql meltdown on
Date: 2003-03-17 06:34:20
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
"Neil Conway" <neilc(at)samurai(dot)com> writes:
> Sean Chittenden said:
> A "select count(*) FROM tblwordidx" initially took about 1 second to
> return a count of 2 million but after a few months it took several
> minutes of really hard HDD grinding.
>> That's because there are dead entries in the index that weren't being
>> reused or cleaned up.  As I said, this has been fixed.

> That's doubtful: "select count(*) FROM foo" won't use an index.

To know what's going on, as opposed to guessing about it, we'd need to
know something about the physical sizes of the table and its indexes.
"vacuum verbose" output would be instructive...

But my best theorizing-in-advance-of-the-data guess is that Logan's
FSM settings are too small, causing free space to be leaked over time.
If a vacuum full restores the original performance then that's probably
the right answer.

			regards, tom lane

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