Horton

Re: Accounting of zero-filled buffers in EXPLAIN (BUFFERS)

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, David Rowley <david.rowley@2ndquadrant.com>, Haribabu Kommi <kommi.haribabu@gmail.com>, Andres Freund <andres@anarazel.de>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-11-23T07:39:13Z
Lists: pgsql-hackers

Attachments

On Mon, Nov 19, 2018 at 5:24 PM Kyotaro HORIGUCHI
<horiguchi.kyotaro@lab.ntt.co.jp> wrote:
> At Sat, 17 Nov 2018 11:15:54 -0300, Alvaro Herrera <alvherre@2ndquadrant.com> wrote in <20181117141554.4dkx2u4j6md3bqdh@alvherre.pgsql>
> > Is this patch committable now?
>
> I don't think so. We should make a decision on a point.
>
> I was a bit confused (sorry) but IIUIC Haribabu suggested that
> the RBM_ZERO_ON_ERROR case should be included to read (not just
> ignored). I'm on it.  I think that RPM_ZERO_* other than ON_ERROR
> cases could be a kind of hit but I don't insist on it.
>
> So, I think we should decide on at least the ON_ERROR case before
> this becomes commttable.

Agreed, RBM_ZERO_ON_ERROR needs to be counted as a read.  Here's a new
version like that.

> The another counter could be another issue. I don't object to add
> the counter but I'm not sure what is the suitable name.

I think that might be interesting information in the future, but let's
consider that for a later patch.

-- 
Thomas Munro
http://www.enterprisedb.com

Commits

  1. Don't count zero-filled buffers as 'read' in EXPLAIN.