Message-ID: <ed3baa81-7fac-7788-cc12-41e3f7917e34@enterprisedb.com>
Date: Fri, 7 Jan 2022 15:25:28 +0100
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Subject: Re: ICU for global collation
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From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>,
 Daniel Verite <daniel@manitou-mail.org>
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On 04.01.22 17:03, Peter Eisentraut wrote:
>> There are really a lot of places with this new code.  Maybe it could 
>> be some
>> new function/macro to wrap that for the normal case (e.g. not 
>> formatting.c)?
> 
> Right, we could just put this into pg_newlocale_from_collation(), but 
> the comment there says
> 
>   * In fact, they shouldn't call this function at all when they are dealing
>   * with the default locale.  That can save quite a bit in hotspots.
> 
> I don't know how to assess that.

I tested this a bit.  I used the following setup:

create table t1 (a text);
insert into t1 select md5(generate_series(1, 10000000)::text);
select count(*) from t1 where a > '';

And then I changed in varstr_cmp():

         if (collid != DEFAULT_COLLATION_OID)
             mylocale = pg_newlocale_from_collation(collid);

to just

         mylocale = pg_newlocale_from_collation(collid);

I find that the \timing results are indistinguishable.  (I used locale 
"en_US.UTF-8" and made sure that that code path is actually hit.)

Does anyone have other insights?