Re: [Patch] Temporary tables that do not bloat pg_catalog (a.k.a fast temp tables)

From: Andres Freund <andres(at)anarazel(dot)de>
To: Claudio Freire <klaussfreire(at)gmail(dot)com>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Aleksander Alekseev <a(dot)alekseev(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [Patch] Temporary tables that do not bloat pg_catalog (a.k.a fast temp tables)
Date: 2016-08-23 22:34:47
Message-ID: 20160823223447.4bpke3norrf2j2lt@alap3.anarazel.de
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On 2016-08-23 19:33:33 -0300, Claudio Freire wrote:
> On Tue, Aug 23, 2016 at 7:20 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> >> Wouldn't more aggressive vacuuming of catalog tables fix the bloat?
> >
> > Not really in my experience, at least not without more drastic vacuum
> > changes. The issue is that if you have a single "long running"
> > transaction (in some workloads that can even just be a 3 min taking
> > query/xact), nothing will be cleaned up during that time. If you have a
> > few hundred temp tables created per sec, you'll be in trouble even
> > then. Not to speak of the case where you have queries taking hours (say
> > a backup).
>
> Well, my experience isn't as extreme as that (just a few dozen temp
> tables per minute), but when I see bloat in catalog tables it's
> because all autovacuum workers are stuck vacuuming huge tables for
> huge periods of time (hours or days).

Well, that's because our defaults are batshit stupid.

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