Feedback-ID: i0fe9450f:Fastmail
Date: Mon, 2 Mar 2026 08:05:44 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Chao Li <li.evan.chao@gmail.com>
Cc: Corey Huinker <corey.huinker@gmail.com>,
	Postgres hackers <pgsql-hackers@lists.postgresql.org>,
	Tomas Vondra <tomas@vondra.me>
Subject: Re: Defects with invalid stats data for expressions in extended stats
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On Fri, Feb 27, 2026 at 04:33:24PM +0900, Michael Paquier wrote:
> On Fri, Feb 27, 2026 at 02:51:40PM +0800, Chao Li wrote:
>> Here stats itself is destroyed, but memory pointed by
>> stats[0]~stats[i-1] are not free-ed, those memory are returned from
>> examine_attribute() by palloc0_object().
>=20
> I am aware of that.  This is not done on simplicity ground, keeping
> the cleanup of the memory context to ANALYZE in this case.

About this one, something worth noting is the beginning of
do_analyze_rel(), which does the following:
    /*
     * Set up a working context so that we can easily free whatever junk ge=
ts
     * created.
     */
    anl_context =3D AllocSetContextCreate(CurrentMemoryContext,
                                        "Analyze",
                                        ALLOCSET_DEFAULT_SIZES);
    caller_context =3D MemoryContextSwitchTo(anl_context);

So these extra allocations would just be freed under this memory
context umbrella once we are done processing a single relation.  This
works even if we begin to repeat ANALYZE commands that fail to build
some of the stats in a repeated fashion in a single transaction block.
Code simplicity and readability is just a better choice for this path.
--
Michael

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