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Re: Autovacuum cancellation

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, pgsql-patches(at)postgresql(dot)org
Subject: Re: Autovacuum cancellation
Date: 2007-10-27 22:15:12
Message-ID: 1193523312.4242.623.camel@ebony.site (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackerspgsql-patches
On Thu, 2007-10-25 at 17:35 -0400, Tom Lane wrote:
> There's some things still to be desired here: if an autovac process is
> involved in a hard deadlock, the patch doesn't favor zapping it over
> anybody else, nor consider cancelling the autovac as an alternative to
> rearranging queues for a soft deadlock.  But dealing with that will
> open cans of worms that I don't think we want to open for 8.3.

I did look at doing that but decided it would not be appropriate to do
that in all cases. i.e. there are hard deadlock cases where the autovac
can be the head of the lock queue and yet a deadlock still exists
between two other processes. The deadlock detector doesn't get called
twice for the same deadlock, so it wasn't possible to speculatively do
that and then re-catch it second time around.

-- 
  Simon Riggs
  2ndQuadrant  http://www.2ndQuadrant.com


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