| 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 22:20:42 |
| Message-ID: | 20160823222042.ocfleq2dosuhbd3z@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2016-08-23 19:18:04 -0300, Claudio Freire wrote:
> On Tue, Aug 23, 2016 at 7:11 PM, Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> > Could someone please explain how the unlogged tables are supposed to fix the
> > catalog bloat problem, as stated in the initial patch submission? We'd still
> > need to insert/delete the catalog rows when creating/dropping the temporary
> > tables, causing the bloat. Or is there something I'm missing?
Beats me.
> 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).
Andres
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