To: "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
cc: "Josh Berkus" <josh@agliodbs.com>, "Robert Haas" <robertmhaas@gmail.com>,
	pgsql-performance@postgresql.org
Subject: Re: Why we don't want hints Was: Slow count(*) again... 
In-reply-to: <4D53C1C0020000250003A783@gw.wicourts.gov> 
References: <201102012247.p11Ml6u02682@momjian.us>
	<4D48914B.4050403@dunslane.net> <4D489AD1.1010105@vmsinfo.com>
	<AANLkTiknZi97dDwm7sHqy0EL7tpNEP9sY5uPV6AN+q=u@mail.gmail.com>
	<4D499E55.4020107@vmsinfo.com> <4D49A6B9.4060608@2ndquadrant.com>
	<4D49C482.4010707@vmsinfo.com> <4D49F0BA.9000901@2ndquadrant.com>
	<4D4A16BF.1020304@vmsinfo.com> <4D4A4844.3020409@2ndquadrant.com>
	<4D4AD9F6.6040903@vmsinfo.com> <4D4AE16E.9040807@peak6.com>
	<4D4B17B4.9030406@vmsinfo.com> <4D4B1F5B.4060403@peak6.com>
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	<4D4B2E8A.7010402@vmsinfo.com> <4D4B3395.6010007@agliodbs.com>
	<4D4B394E.9080505@vmsinfo.com> <4D4B5A73.3080302@agliodbs.com>
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	<4D53C1C0020000250003A783@gw.wicourts.gov>
Comments: In-reply-to "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
	message dated "Thu, 10 Feb 2011 10:45:20 -0600"
Date: Thu, 10 Feb 2011 12:01:42 -0500
Message-ID: <17455.1297357302@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Robert Haas <robertmhaas@gmail.com> wrote:
>> I don't know exactly what the right solution is off the top of my
>> head, but digging in our heels is not it.
 
> Well, I'm comfortable digging in my heels against doing *lame* hints
> just because "it's what all the other kids are doing," which I think
> is the only thing which would have satisfied the OP on this thread. 

Right.  If someone comes up with a design that avoids the serious
pitfalls of traditional hinting schemes, that'd be great.  But I'm
not interested in implementing Oracle-like hints just because Oracle
has them, which I think was basically what the OP wanted.  I haven't
seen a hinting scheme that didn't suck (and that includes the aspects
of our own current behavior that are hint-like).  I don't say that
there can't be one.

I believe that the FAQ entry is meant to answer people who come along
and say "oh, this is easily solved, just do what $PRODUCT does".  The
generic answer to that is "no, it's not that easy".  But maybe the FAQ
should be rephrased to be more like "we don't want traditional hints
because of problems X, Y, and Z.  If you have an idea that avoids those
problems, let us know."

			regards, tom lane