From: Tom Lane <tgl@sss.pgh.pa.us>
To: devops@key2asset.com
cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18870: weird behavior with regexp_replace
In-reply-to: <18870-70cd953a0c92c20e@postgresql.org>
References: <18870-70cd953a0c92c20e@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Thu, 27 Mar 2025 13:43:50 -0000"
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Date: Thu, 27 Mar 2025 17:23:58 -0400
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PG Bug reporting form <noreply@postgresql.org> writes:
> select regexp_replace(LOWER('=C3=96rebro'), '\W', '_', 'g')  in postgres=
 15 the
> result is =C3=B6rebro which is correct since =C3=B6 should fit in the \w=
 for a
> regex.
> select regexp_replace(LOWER('=C3=96rebro'), '\W', '_', 'g') --> since po=
stgres 17
> the result is _rebro which is incorrect since \w should also contain
> characters like =C3=B6, =C3=A4, =C3=AB.

This most likely indicates that you've got a different database
collation selected in the v17 installation.  Postgres defers to
the LC_CTYPE setting (or, in some configurations, the ICU collation)
to decide what is a letter.  See

https://www.postgresql.org/docs/current/charset.html

psql's "\l" command will give a quick overview of what collations
you have selected.

			regards, tom lane