Feedback-ID: i0fe9450f:Fastmail
Date: Tue, 5 Dec 2023 12:05:26 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Jerry Brenner <jbrenner@guidewire.com>,
	pgsql-performance@lists.postgresql.org
Subject: Re: Does Postgres have consistent identifiers (plan hash value) for
 explain plans?
Message-ID: <ZW6TdlN7Im7h2KCd@paquier.xyz>
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On Mon, Dec 04, 2023 at 09:57:24AM -0500, Tom Lane wrote:
> Jerry Brenner <jbrenner@guidewire.com> writes:
>> Both Oracle and SQL Server have
>> consistent hash values for query plans and that makes it easy to identify
>> when there are multiple plans for the same query.  Does that concept exi=
st
>> in later releases of Postgres (and is the value stored in the json expla=
in
>> plan)?
>=20
> No, there's no support currently for obtaining a hash value that's
> associated with a plan rather than an input query tree.

PlannerGlobal includes a no_query_jumble that gets inherited by all
its lower-level nodes, so adding support for hashes compiled from
these node structures would not be that complicated.  My point is that
the basic infrastructure is in place in the tree to be able to do
that, and it should not be a problem to even publish the compiled
hashes in EXPLAIN outputs, behind an option of course.
--
Michael

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