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Date: Fri, 26 Dec 2025 08:01:41 +0900
From: Michael Paquier <michael@paquier.xyz>
To: =?utf-8?B?0JDQvdC00YDQtdC5INCa0LDQt9Cw0YfQutC+0LI=?=
 <andrey.kazachkov@tantorlabs.ru>
Cc: Sami Imseih <samimseih@gmail.com>, Lukas Fittl <lukas@fittl.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Marko M <marko@pganalyze.com>
Subject: Re: [PATCH] Optionally record Plan IDs to track plan changes for a
 query
Message-ID: <aU3CVSkKiyLwfreT@paquier.xyz>
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On Thu, Dec 25, 2025 at 05:33:11PM +0300, =D0=90=D0=BD=D0=B4=D1=80=D0=B5=D0=
=B9 =D0=9A=D0=B0=D0=B7=D0=B0=D1=87=D0=BA=D0=BE=D0=B2 wrote:
> I=E2=80=99ve been testing the proposed v5 plan id work and found out inst=
ability of
> computing the plan identifier after feeding different query texts that
> produces the same physical plan trees but with different plan ids. The ma=
in
> pattern regards with fields of Plan node structures that depend on positi=
ons of
> RTEs in a RTE list.

FWIW, I don't think that we have a clear agreement about what would be
a good enough ID for plan trees, as it may be also a per-vendor
computation that fills specific user requirements.

+    /*
+     * COMPUTE_PLAN_ID_REGRESS means COMPUTE_PLAN_ID_YES, but we don't show
+     * the queryid in any of the EXPLAIN plans to keep stable the results
+     * generated by regression test suites.
+     */
+    if (es->verbose && queryDesc->plannedstmt->planId !=3D UINT64CONST(0) =
&&
+        compute_plan_id !=3D COMPUTE_PLAN_ID_REGRESS)
+    {
+        /*
+         * Output the queryid as an int64 rather than a uint64 so we match
+         * what would be seen in the BIGINT pg_stat_activity.plan_id colum=
n.
+         */
+        ExplainPropertyInteger("Plan Identifier", NULL,
+                               queryDesc->plannedstmt->planId, es);
+    }

Now, looking at this block of code, I am wondering if you don't have a
point here even without compute_plan_id..  Could there be merit in
showing this information for an EXPLAIN if this field is not zero?
With EXPLAIN being pluggable in a hook, I doubt that it matters much,
but I am wondering if providing this information could make the work
of some extensions easier.
--
Michael

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