From: | torikoshia <torikoshia(at)oss(dot)nttdata(dot)com> |
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To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
Cc: | legrand legrand <legrand_legrand(at)hotmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Is it useful to record whether plans are generic or custom? |
Date: | 2020-11-17 14:21:53 |
Message-ID: | 5904ec21e0fcdd1063d9ea7f60ca83c0@oss.nttdata.com |
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Lists: | pgsql-hackers |
On 2020-11-12 14:23, Pavel Stehule wrote:
> yes, the plan self is very interesting information - and information
> if plan was generic or not is interesting too. It is other dimension
> of query - maybe there can be rule - for any query store max 100 most
> slows plans with all attributes. The next issue is fact so first first
> 5 execution of generic plans are not generic in real. This fact should
> be visible too.
Thanks!
However, AFAIU, we can know whether the plan type is generic or custom
from the plan information as described in the manual.
-- https://www.postgresql.org/docs/devel/sql-prepare.html
> If a generic plan is in use, it will contain parameter symbols $n,
> while a custom plan will have the supplied parameter values substituted
> into it.
If we can get the plan information, the case like 'first 5 execution
of generic plans are not generic in real' does not happen, doesn't it?
Regards,
--
Atsushi Torikoshi
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