Horton

Re: EXPLAIN BUFFERS

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Takahiro Itagaki <itagaki.takahiro@oss.ntt.co.jp>
Cc: Euler Taveira de Oliveira <euler@timbira.com>, Greg Smith <greg@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@commandprompt.com>, Jeff Janes <jeff.janes@gmail.com>, Pgsql Hackers <pgsql-hackers@postgresql.org>
Date: 2009-12-14T04:13:11Z
Lists: pgsql-hackers 
On Sun, Dec 13, 2009 at 10:00 PM, Takahiro Itagaki
<itagaki.takahiro@oss.ntt.co.jp> wrote:
>> Two other thoughts:
>>
>> 1. It doesn't appear that there is any provision to ever zero
>> pgBufferUsage.  Shouldn't we do this, say, once per explain, just to
>> avoid the possibility of overflowing the counters?
>
> I think the overflowing will not be a problem because we only use
> the differences of values. The delta is always corrent unless we use
> 2^32 buffer accesses during one execution of a node.

Hmm... you might be right.  I'm not savvy enough to know whether there
are any portability concerns here.

Anyone else know?

...Robert