From: | Michael Meskes <meskes(at)postgresql(dot)org> |
---|---|
To: | Boszormenyi Zoltan <zb(at)cybertec(dot)at> |
Cc: | Noah Misch <noah(at)leadboat(dot)com>, Michael Meskes <meskes(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, PG Hackers <pgsql-hackers(at)postgresql(dot)org>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us> |
Subject: | Re: ECPG FETCH readahead |
Date: | 2012-04-16 02:46:36 |
Message-ID: | 20120416024636.GA4536@feivel.credativ.lan |
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Lists: | pgsql-hackers |
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
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