From: | Julien Rouhaud <rjuju123(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Make EXPLAIN generate a generic plan for a parameterized query |
Date: | 2022-10-11 16:03:48 |
Message-ID: | 20221011160348.dptd53h4bfg7cv5v@jrouhaud |
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Lists: | pgsql-hackers |
On Tue, Oct 11, 2022 at 09:49:14AM -0400, Tom Lane wrote:
>
> If you're trying to investigate custom-plan behavior, then you
> need to supply concrete parameter values somewhere, so I think
> this approach is fine for that case. (Shoehorning parameter
> values into EXPLAIN options seems like it'd be a bit much.)
> However, investigating generic-plan behavior this way is tedious,
> since you have to invent irrelevant parameter values, plus mess
> with plan_cache_mode or else run the explain half a dozen times.
> So I can get behind having a more convenient way for that.
One common use case is tools identifying a slow query using pg_stat_statements,
identifying some missing indexes and then wanting to check whether the index
should be useful using some hypothetical index.
FTR I'm working on such a project and for now we have to go to great lengths
trying to "unjumble" such queries, so having a way to easily get the answer for
a generic plan would be great.
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