| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Mark Mielke <mark(at)mark(dot)mielke(dot)cc> |
| Cc: | Jeroen Vermeulen <jtv(at)xs4all(dot)nl>, Alex Hunsaker <badalex(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, 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 18:59:22 |
| Message-ID: | 2060.1267210762@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Mark Mielke <mark(at)mark(dot)mielke(dot)cc> writes:
> Just to point out that I agree, and as per my original post, I think the
> only time prepared statements should be re-planned for the statistics
> case, is after 'analyze' has run. That sounds like a quicker solution,
> and a much smaller gain. After 'analyze' of an object, invalidate all
> cached plans for prepared statements that rely on that object and
> require a re-plan.
Please note that that has been happening since 8.3, which is probably
why you haven't detected a problem.
> ... It's walking around the problem
> that the idea of a generic plan is just wrong. The only time a generic
> plan is right, is when the specific plan would result in the same.
I think that's a significant overstatement. There are a large number
of cases where a custom plan isn't worth it, even if it doesn't generate
exactly the same plan.
regards, tom lane
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