From: Tom Lane <tgl@sss.pgh.pa.us>
To: Kamen Kalchev <kalchev035@gmail.com>
cc: pgsql-general@postgresql.org, abubakarm94@gmail.com
Subject: Re: glibc 2.35-2.39 upgrade requirements
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Comments: In-reply-to Kamen Kalchev <kalchev035@gmail.com>
	message dated "Thu, 16 Jan 2025 18:44:18 +0200"
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Date: Fri, 17 Jan 2025 10:27:04 -0500
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Kamen Kalchev <kalchev035@gmail.com> writes:
> Hi everyone, we're planning to upgrade the OS running Postgres from ubuntu
> jammy to ubuntu noble. As part of the OS change, the glibc version will be
> changed from glibc 2.35 to glibc 2.39..
> Can someone confirm if changing the glibc between those versions will
> require a full reindex of the Postgres cluster?

Maybe, maybe not.  According to [1], the last glibc collation change
that the PG community really noticed was in glibc 2.28.  So maybe
there weren't any significant changes between 2.35 and 2.39.  The
conservative path would certainly be to reindex all textual columns
(though you can skip any that have collation "C").

If you feel a need to try to avoid that, you could dump some of your
textual columns into files and sort those using sort(1) on both
old and new systems.  (Be sure that the LANG/LC_xxx environment
matches what you use for the database.)  If the results are different
then you definitely need to reindex; if they are the same then maybe
you're okay.  Pay particular attention to columns containing
punctuation or non-ASCII characters, as those are the areas most
likely to see changes.

			regards, tom lane

[1] https://wiki.postgresql.org/wiki/Locale_data_changes