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From: Pavel Stehule <[email protected]>
To: Jeff Davis <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Thomas Munro <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: [email protected]
Subject: Re: Move defaults toward ICU in 16?
Date: Sat, 18 Feb 2023 05:52:54 +0100
Message-ID: <CAFj8pRAGgzyyEOBjkuNCo2tXnyzmENPF0YjtpK5vtqQ2efsviw@mail.gmail.com> (raw)
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pá 17. 2. 2023 v 21:43 odesílatel Jeff Davis <[email protected]> napsal:

> On Fri, 2023-02-17 at 18:27 +0100, Pavel Stehule wrote:
> > Today I tested icu for Czech sorting. It is a little bit slower, but
> > not too much, but it produces partially different results.
>
> Thank you for trying it.
>
> If it's a significant slowdown, can you please send more information?
> ICU version, libc version, and testcase?
>

no - this slowdown is not significant - although 1% can looks too much -
but it is just two ms

It looks so libicu has little bit more expensive initialization, but the
execution is little bit faster

But when I try to repeat the measurements, the results are very unstable on
my desktop :-/

SELECT * FROM obce ORDER BY nazev LIMIT 10 // is faster with glibc little
bit
SELECT * FROM obce ORDER BY nazev // is faster with libicu

You can download dataset https://pgsql.cz/files/obce.sql

It is table of municipalities in czech republic (real names) - about 6000
rows

I use fedora 37 - so libicu 71.1, glibc 2.36

Regards

Pavel



>
> > select row_number() over (order by nazev collate "cs-x-icu"), nazev
> > from obce
> > except select row_number() over (order by nazev collate "cs_CZ"),
> > nazev from obce;
> >
> > returns a not empty set. So minimally for Czech collate, an index
> > rebuild is necessary
>
> Yes, that's true of any locale change, provider change, or even
> provider version change.
>
>
> --
> Jeff Davis
> PostgreSQL Contributor Team - AWS
>
>
>


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