From: | Grigory Smolkin <g(dot)smolkin(at)postgrespro(dot)ru> |
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To: | pgsql-bugs(at)lists(dot)postgresql(dot)org, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
Subject: | Re: long analyze, libc bug and libicu |
Date: | 2018-07-07 09:18:59 |
Message-ID: | 2da0c289-bfc8-a40f-e13b-1b2943746e9e@postgrespro.ru |
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On 07/07/2018 10:10 AM, Peter Eisentraut wrote:
> On 05.07.18 17:05, Grigory Smolkin wrote:
>> Why ANALYZE igrones column COLLATE?
> I think the statistics would be mostly the same independent of which
> collation you use. This could possibly be refined, but I don't think
> it's a major problem right now.
>
Thank you for your interest in this problem!
> I think the statistics would be mostly the same independent of which
> collation you use.
I assumed that one of the goals of using libicu is to be independent
from libc collation and it`s bugs and inconsistencies, but current
ANALYZE forced to use libc anyway, which undermines that goal.
> This could possibly be refined, but I don't think
> it's a major problem right now.
It`s a major problem to people, who use Thai alphabet.
In attachment there is a data sample(33MB on my machine). ANALYZE`ing it
comes up with following results:
postgres=# ANALYZE t_icu_coll;
ANALYZE
Time: 2252086.648 ms
37minutes on 33MB table is painful. On big tables autovacuum ANALYZE
goes for hours, starving autovacuum VACUUM for worker
slots(autovacuum_max_workers).
Another major problem is that in strol_l() backend process ignores
pg_terminate_backend()/pg_cancel_backend() functions.
With attached patch this problem goes away:
postgres=# analyze t_icu_coll;
ANALYZE
Time: 161.419 ms
--
Grigory Smolkin
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
Attachment | Content-Type | Size |
---|---|---|
t_icu_coll.sql.gz | application/gzip | 3.2 MB |
analyze_honour_column_collation.patch | text/x-patch | 675 bytes |
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