Re: Problem in 'ORDER BY' of a column using a created collation?

From: jian he <jian(dot)universality(at)gmail(dot)com>
To: Nishant Sharma <nishant(dot)sharma(at)enterprisedb(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Problem in 'ORDER BY' of a column using a created collation?
Date: 2025-08-25 15:28:49
Message-ID: CACJufxG1W9vLOB=svB7oQiTH0ooK-wnbAjwru45LVOb_goEW7A@mail.gmail.com
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On Mon, Aug 25, 2025 at 3:52 PM Nishant Sharma
<nishant(dot)sharma(at)enterprisedb(dot)com> wrote:
>
>
> Experiment 1:-
> SQL File : PG_Exp_1.sql
>
> Actual Output : PG_Exp_1.out
>
> Created COLLATION : CREATE COLLATION test_coll (
> provider = icu, locale = 'ja-u-kr-latn-digit');
>
> Experiment 2:-
> SQL File : PG_Exp_2.sql
>
> Actual Output : PG_Exp_2.out
>
> Created 'COLLATION' : CREATE COLLATION test_coll (
> provider = icu, locale = 'ja-u-kr-digit-latn');
>
> 'SELECT' Queries : Same as 'Experiment 1'.
>
> Expectation : All digits should come before all alphabets.
>
> Need help in confirming why 'Experiment 1' is behaving as mentioned
> above -
> 1. If our expectation of 'Experiment 1' is wrong?

I am not sure.
but for the 'Experiment 1', I can use the following collation to get
the expected result you want, I think.
CREATE COLLATION x (provider = icu, locale = 'und-u-latn-digit');

------both two SELECTS, numeric first then alphabets
SELECT * FROM test_table ORDER BY value1 COLLATE x, value2 COLLATE x;
SELECT * FROM test_table ORDER BY value2 COLLATE x, value1 COLLATE x;

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