Re: Report planning memory in EXPLAIN ANALYZE

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
Cc: jian he <jian(dot)universality(at)gmail(dot)com>, Andrei Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru>, Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Report planning memory in EXPLAIN ANALYZE
Date: 2023-12-17 16:27:47
Message-ID: 202312171627.yad4c73mi4te@alvherre.pgsql
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OK, I propose the following further minor tweaks. (I modified the docs
following the wording we have for COSTS and BUFFERS).

There are two things that still trouble me a bit. First, we assume that
the planner is using an AllocSet context, which I guess is true, but if
somebody runs the planner in a context of a different memcxt type, it's
going to be a problem. So far we don't have infrastructure for creating
a context of the same type as another context. Maybe it's too fine a
point to worry about, for sure.

The other question is about trying to support the EXPLAIN EXECUTE case.
Do you find that case really useful? In a majority of cases planning is
not going to happen because it was already done by PREPARE (where we
_don't_ report memory, because we don't have EXPLAIN there), so it seems
a bit weird. I suppose you could make it useful if you instructed the
user to set plan_cache_mode to custom, assuming that does actually work
(I didn't try).

Álvaro Herrera 48°01'N 7°57'E —
"El hombre nunca sabe de lo que es capaz hasta que lo intenta" (C. Dickens)

Attachment Content-Type Size
fixups.txt text/plain 2.7 KB

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