From: Tom Lane <tgl@sss.pgh.pa.us>
To: James Coleman <jtc331@gmail.com>
cc: =?UTF-8?Q?Juan_Jos=C3=A9_Santamar=C3=ADa_Flecha?=
 <juanjo.santamaria@gmail.com>,
        Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        Mark Dilger <mark.dilger@enterprisedb.com>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        Arthur Zakirov <zaartur@gmail.com>,
        Tomas Vondra <tomas.vondra@2ndquadrant.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Allow to_date() and to_timestamp() to accept localized names
In-reply-to: <21675.1583685539@sss.pgh.pa.us>
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Sun, 08 Mar 2020 12:38:59 -0400"
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Date: Sun, 08 Mar 2020 14:19:46 -0400
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I wrote:
> James Coleman <jtc331@gmail.com> writes:
>> I'm still interested in understanding why we're using the ISO locale
>> instead of the utf8 one in a utf8-labeled test though.

> We are not.  My understanding of the rules about this is that the
> active LC_CTYPE setting determines the encoding that libc uses,
> period.  The encoding suffix on the locale name only makes a
> difference when LC_CTYPE is being specified (or derived from LANG or
> LC_ALL), not any other LC_XXX setting --- although for consistency
> they'll let you include it in any LC_XXX value.

Oh wait --- I'm wrong about that.  Looking at the code in pg_locale.c,
what actually happens is that we get data in the codeset implied by
the LC_TIME setting and then translate it to the database encoding
(cf commit 7ad1cd31b).  So if bare "tr_TR" is taken as implying
iso-8859-9, which seems likely (it appears to work that way here,
anyway) then this test is exercising the codeset translation path.
We could change the test to say 'tr_TR.utf8' but that would give us
less test coverage.

			regards, tom lane