Re: Some belated patch review for "Buffers" explain analyze patch

From: Greg Stark <stark(at)mit(dot)edu>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Josh Berkus <josh(at)agliodbs(dot)com>, "<pgsql-hackers(at)postgresql(dot)org>" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Some belated patch review for "Buffers" explain analyze patch
Date: 2010-02-09 23:57:35
Message-ID: 407d949e1002091557q3936cfb0l136033a9de2959e6@mail.gmail.com
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On Tue, Feb 9, 2010 at 10:42 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> A more important point is that it would be a nontrivial change, both as
>> to code and documentation, and it's too late for such in 9.0.  So what
>> we ought to be confining the discussion to right now is what 9.0 should
>> print here.
>
> It's exactly as nontrivial as the proposed change in the other direction.

I think it's non-triviality lies in the user-visible effects. Ie, we
won't have a release cycle of experience with the change ourselves to
see if we really like the new behaviour and can live with it.

I'm not sure where I stand myself as I find the averaging quite
confusing myself. I'm not sure how confusing it would be to change
though.

The total i/o done is likely to be something you want to compare with
some other metric like output from iostat or knowledge of how much
bandwidth your i/o system can provide so it does seem like totals are
relevant.

I think I'm leaning -- slightly -- towards calling out the discrepancy
by naming it something like "Total Buffer Usage:". But I could be
convinced otherwise.

--
greg

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