Feedback-ID: i0fe9450f:Fastmail
Date: Thu, 4 Apr 2024 08:34:04 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Melih Mutlu <m.melihmutlu@gmail.com>
Cc: torikoshia <torikoshia@oss.nttdata.com>,
	Andres Freund <andres@anarazel.de>,
	Stephen Frost <sfrost@snowman.net>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Parent/child context relation in pg_get_backend_memory_contexts()
Message-ID: <Zg3nbJPBTqDa4yGG@paquier.xyz>
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On Wed, Apr 03, 2024 at 04:20:39PM +0300, Melih Mutlu wrote:
> Michael Paquier <michael@paquier.xyz>, 14 =C5=9Eub 2024 =C3=87ar, 10:23 t=
arihinde
> =C5=9Funu yazd=C4=B1:
>> I was reading the patch, and using int[] as a representation of the
>> path of context IDs up to the top-most parent looks a bit strange to
>> me, with the relationship between each parent -> child being
>> preserved, visibly, based on the order of the elements in this array
>> made of temporary IDs compiled on-the-fly during the function
>> execution.  Am I the only one finding that a bit strange?  Could it be
>> better to use a different data type for this path and perhaps switch
>> to the names of the contexts involved?
>=20
> Do you find having the path column strange all together? Or only using
> temporary IDs to generate that column? The reason why I avoid using conte=
xt
> names is because there can be multiple contexts with the same name. This
> makes it difficult to figure out which context, among those with that
> particular name, is actually included in the path. I couldn't find any
> other information that is unique to each context.

I've been re-reading the patch again to remember what this is about,
and I'm OK with having this "path" column in the catalog.  However,
I'm somewhat confused by the choice of having a temporary number that
shows up in the catalog representation, because this may not be
constant across multiple calls so this still requires a follow-up
temporary ID <-> name mapping in any SQL querying this catalog.  A
second thing is that array does not show the hierarchy of the path;
the patch relies on the order of the elements in the output array
instead.
--
Michael

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