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Re: First steps with 8.3 and autovacuum launcher

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, Guillaume Smet <guillaume(dot)smet(at)gmail(dot)com>, "Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: First steps with 8.3 and autovacuum launcher
Date: 2007-10-04 18:33:16
Message-ID: 20071004183316.GB21453@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane escribió:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > Gregory Stark escribi:
> >> A crazy idea I just had -- what if you roll this into the deadlock check? So
> >> after waiting on the lock for 1s it wakes up, finds that the holder it's
> >> waiting on is an autovacuum process and cancels it instead of finding no
> >> deadlock.
> 
> > Another crazy idea is to have some sort of "blacklist" of tables in
> > shared memory.  Any autovacuum process would skip those tables.
> 
> The deadlock check idea sounds promising to me, not least because it
> avoids adding any cycles in performance-critical paths.  I'm not certain
> how easy it'd be to fold the idea into the checker though.  That
> logic is pretty complicated :-( and I'm not sure that it makes a
> consistent effort to visit every possible blocker.

The idea sounds interesting, but I am not at all sure how to fit it in
the deadlock code.

I am totally uninclined to mess with this stuff.  I am barely aware of
what exactly is it doing; I don't have the slightest idea how to modify
it to cancel autovacs.  Furthermore it sounds very much like a layering
violation (what is deadlock.c doing with autovac processes anyway).

-- 
Alvaro Herrera                        http://www.advogato.org/person/alvherre
"Pensar que el espectro que vemos es ilusorio no lo despoja de espanto,
sólo le suma el nuevo terror de la locura" (Perelandra, CSLewis)

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Next:From: Simon RiggsDate: 2007-10-04 18:40:46
Subject: Re: First steps with 8.3 and autovacuum launcher
Previous:From: Tom LaneDate: 2007-10-04 18:22:40
Subject: Re: Not *quite* there on ecpg fixes

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