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Re: Avoiding bad prepared-statement plans.

From: Alex Hunsaker <badalex(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeroen Vermeulen <jtv(at)xs4all(dot)nl>, Greg Stark <gsstark(at)mit(dot)edu>, Bart Samwel <bart(at)samwel(dot)tk>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Avoiding bad prepared-statement plans.
Date: 2010-02-26 20:02:40
Message-ID: 34d269d41002261202n492cc8bcoefa6ec77e507fb58@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, Feb 26, 2010 at 09:50, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Feb 26, 2010 at 1:29 AM, Alex Hunsaker <badalex(at)gmail(dot)com> wrote:
>> Prepared plans + exec plan (new guc/ protocol thing):
>>  Use: not quite sure
>>  Problems: slow because it would replan every time
>>  Solutions: use a prepared plan with the appropriate things not
>> parametrized...?
>>
>> [ aka we already have this, its called dont use a prepared statement ]
>
> The point is sometimes you'd like to replan every time, but not
> reparse every time.  There's no way to do that ATM.

So what you save on parse time?  Maybe that's worth it.  I've never
run the numbers nor have I seen them in this thread.  I probably
missed em...  My _hunch_ is planning will on average take
significantly longer than parse time (read in the noise of plan time).
 But that's unfounded :)  I can certainly imagine cases where you have
HUGE queries where the parse time too slow-- wont the plan most of the
time be an order of magnitude slower?  Anyway Ill stop until I get a
chance to do _some_ kind of benchmarking, I'm really quite clueless
here.

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