| From: | Yeb Havinga <yebhavinga(at)gmail(dot)com> |
|---|---|
| To: | Mark Mielke <mark(at)mark(dot)mielke(dot)cc> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Jeroen Vermeulen <jtv(at)xs4all(dot)nl>, Alex Hunsaker <badalex(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 20:46:27 |
| Message-ID: | 4B883323.5090701@gmail.com |
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| Lists: | pgsql-hackers |
Mark Mielke wrote:
> On 02/26/2010 03:11 PM, Yeb Havinga wrote:
>> Or instead of letting users give the distribution, gather it
>> automatically in some plan statistics catalog? I suspect in most
>> applications queries stay the same for months and maybe years, so
>> after some number of iterations it is possible to have decent call
>> statistics / parameter distributions. Maybe the the parameter value
>> distribution could even be annotated with actual cached plans.
>
> The problem with the last - actual cached plans - is that it implies
> the other aspect I have been suggesting: In order to have a custom
> cached plan, the primary model must be to use custom plans. If
> PREPARE/EXECUTE uses generic plans normally, than the only cached
> plans available will be generic plans.
I should have been clearer, with 'actual cached plans' I meant 'cached
plans planned with actual parameters' or 'cached custom plans'. It makes
no sense to annotate points or intervals in a gathered value
distribution with generic plans.
regards,
Yeb Havinga
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