Date: Fri, 30 Sep 2022 14:47:28 -0700
From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Stephen Frost <sfrost@snowman.net>,
	Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>,
	"David G. Johnston" <david.g.johnston@gmail.com>,
	Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	Michael Paquier <michael@paquier.xyz>,
	Robert Haas <robertmhaas@gmail.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: predefined role(s) for VACUUM and ANALYZE
Message-ID: <20220930214728.GA177925@nathanxps13>
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On Fri, Sep 30, 2022 at 04:15:24PM -0400, Tom Lane wrote:
> In view of the recent mess around bigint relfilenodes, it seems to me
> that we shouldn't move forward with widening AclMode unless somebody
> runs down which structs will get wider (or more aligned) and how much
> that'll cost us.  Maybe it's not a problem, but it could do with an
> explicit look at the point.

The main one I see is AclItem, which increases from 12 bytes to 16 bytes.
AFAICT all of the catalogs that store aclitem arrays have the aclitem[]
column marked extended, so they are compressed or moved out-of-line as
needed, too.  The only other structs I've spotted that make use of AclMode
are InternalGrant and InternalDefaultACL.  I haven't identified anything
that leads me to believe there are alignment problems or anything else
comparable to the issues listed in the relfilenode thread [0], but I could
be missing something.  Did you have something else in mind you think ought
to be checked?  I'm not sure my brief analysis here suffices.

[0] https://postgr.es/m/CA%2BTgmoaa9Yc9O-FP4vS_xTKf8Wgy8TzHpjnjN56_ShKE%3DjrP-Q%40mail.gmail.com

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com