From: Michael Meskes <meskes@postgresql.org>
To: Boszormenyi Zoltan <zb@cybertec.at>
Cc: Noah Misch <noah@leadboat.com>
Cc: Michael Meskes <meskes@postgresql.org>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: PG Hackers <pgsql-hackers@postgresql.org>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: Bruce Momjian <bruce@momjian.us>
Subject: Re: ECPG FETCH readahead
Date: Mon, 16 Apr 2012 04:46:36 +0200
Message-ID: <20120416024636.GA4536@feivel.credativ.lan> (raw)
In-Reply-To: <4F847453.9060200@cybertec.at>
References: <4F74E6A7.8040204@cybertec.at>
<20120407112008.GA2286@feivel.credativ.lan>
<20120407155042.GB11987@tornado.leadboat.com>
<20120408142501.GA21513@feivel.credativ.lan>
<4F81BE55.1010904@cybertec.at>
<20120408173859.GA4915@feivel.credativ.lan>
<4F83E2B9.3030302@cybertec.at>
<20120410143722.GC6129@tornado.leadboat.com>
<20120410145501.GA11554@feivel.credativ.lan>
<4F847453.9060200@cybertec.at>
On Tue, Apr 10, 2012 at 07:56:35PM +0200, Boszormenyi Zoltan wrote:
> With the above, it would be possible to use a comma separated list of "-r"
> suboptions, e.g. "-r prepare,questionmarks,readahead=16" in one option.
Yes, that sounds like a good plan. But of course it's outside the scope of this
patch, so we can add this later on.
> - Also added a note to the documentation about a possible performance trap
> if a previously written ECPG application uses its own custom readahead via
> multi-row FETCH statements.
I didn't know that before you send this patch. Noah, did you?
Frankly, I don't like this at all. If I got it right that means a FETCH N is
essantially computed as N times FETCH 1 unless you either add a non-standard
option to the DECLARE statement or you add a command-line option to ecpg. Did I
get that right?
If so we would deliberately make ecpglib work incorrectly and remove
performance. Why is that? I'm interested in what others think, but to me that
sounds like a show-stopper.
Michael
--
Michael Meskes
Michael at Fam-Meskes dot De, Michael at Meskes dot (De|Com|Net|Org)
Michael at BorussiaFan dot De, Meskes at (Debian|Postgresql) dot Org
Jabber: michael.meskes at googlemail dot com
VfL Borussia! Força Barça! Go SF 49ers! Use Debian GNU/Linux, PostgreSQL
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To: pgsql-hackers@postgresql.org
Cc: meskes@postgresql.org, zb@cybertec.at, noah@leadboat.com, robertmhaas@gmail.com, heikki.linnakangas@enterprisedb.com, bruce@momjian.us
Subject: Re: ECPG FETCH readahead
In-Reply-To: <20120416024636.GA4536@feivel.credativ.lan>
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