Re: EXPLAIN BUFFERS

From: Euler Taveira de Oliveira <euler(at)timbira(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, Greg Smith <greg(at)2ndquadrant(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: EXPLAIN BUFFERS
Date: 2009-12-10 14:03:30
Message-ID: 4B20FFB2.5040808@timbira.com
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Robert Haas escreveu:
> I'm not sure whether this is a good idea or not. Let me read the
> patch. I'm not sure an EXPLAIN option is really an adequate
> substitute for log_statement_stats - the latter will let you get stats
> for all of your queries automatically, I believe, and might still be
> useful as a quick and dirty tool.
>
Why? If you want this information for all of your queries, you can always set
auto_explain.log_min_duration to 0. But if you're suggesting that we should
maintain log_statement_stats (that was not I understand from Tom's email [1]),
it's not that difficult to a change ShowBufferUsage().

> We certainly should NOT count on dtrace as a substitute for anything.
> It's not available on Windows, or all other platforms either.
>
But we can always count on EXPLAIN BUFFERS. Remember that some monitoring
tasks are _only_ available via DTrace.

> I still think this is a bad format. Instead of putting "(" and ")"
> around each phrase, can't we just separate them with a "," or ";"?
>
We already use ( and ) to group things. I don't remember us using , or ; in
any output node. The suggested output is intuitive and similar to other nodes
patterns.

[1] http://archives.postgresql.org/pgsql-hackers/2009-10/msg00718.php

--
Euler Taveira de Oliveira
http://www.timbira.com/

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