Re: vacuum bug

From: "Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: vacuum bug
Date: 2003-07-02 01:41:08
Message-ID: 04ef01c3403b$043312d0$2800a8c0@mars
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> There would be *zero* activity on a table undergoing vacuum full, unless
> your app has found a way around vacuum full's exclusive lock. You sure
> this wasn't a plain vacuum?

Hmm...correct. So I don't know what happened.

> > Then vacuum full failed after a while:
> > ERROR: simple_heap_update: tuple concurrently updated
>
> Were you doing VACUUM ANALYZEs?

The background vacuum was doing analyze, the full one was not.

> It's possible for two concurrent VACUUM ANALYZEs of the same table
> to get this failure from trying to concurrently update the same row in
> pg_statistic. (The cure for this seems worse than the disease: AFAICS
> you'd have to prevent *all* concurrent updates of pg_statistic by
> grabbing a table-level lock. So we just live with one of the analyzes
> reporting a failure. All the useful work gets done anyway, by one
> transaction or the other.)

Hmmm...I don't see why I would have had two concurrent analyzes going on...

I guess there's not enough info to diagnose it anyway...

Chris

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