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From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Cc: Haribabu Kommi <kommi.haribabu@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Per table autovacuum vacuum cost limit behaviour strange
Date: Wed, 27 Aug 2014 10:51:11 +1200
Message-ID: <53FD0F5F.7000002@catalyst.net.nz> (raw)
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On 27/08/14 10:27, Alvaro Herrera wrote:
> Alvaro Herrera wrote:
>
>> So my proposal is a bit more complicated.  First we introduce the notion
>> of a single number, to enable sorting and computations: the "delay
>> equivalent", which is the cost_limit divided by cost_delay.
>
> Here's a patch that implements this idea.  As you see this is quite a
> bit more complicated that Haribabu's proposal.
>
> There are two holes in this:
>
> 1. if you ALTER DATABASE to change vacuum delay for a database, those
> values are not considered in the global equiv delay.  I don't think this
> is very important and anyway we haven't considered this very much, so
> it's okay if we don't handle it.
>
> 2. If you have a "fast worker" that's only slightly faster than regular
> workers, it will become slower in some cases.  This is explained in a
> FIXME comment in the patch.
>
> I don't really have any more time to invest in this, but I would like to
> see it in 9.4.  Mark, would you test this?  Haribabu, how open are you
> to fixing point (2) above?
>

Thanks Alvaro - I will take a look.

regards

Mark



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