From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Move defaults toward ICU in 16? |
Date: | 2023-02-18 04:52:54 |
Message-ID: | CAFj8pRAGgzyyEOBjkuNCo2tXnyzmENPF0YjtpK5vtqQ2efsviw@mail.gmail.com |
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pá 17. 2. 2023 v 21:43 odesílatel Jeff Davis <pgsql(at)j-davis(dot)com> 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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