Message-ID: <1309ac58-2a66-973a-02c7-9ec8182d05bf@cloud.gatewaynet.com>
Date: Fri, 15 Sep 2023 23:36:48 +0300
MIME-Version: 1.0
Subject: Re: pgsql 10.23 , different systems, same table , same plan,
 different Buffers: shared hit
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To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@lists.postgresql.org
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From: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
In-Reply-To: <3666541.1694806930@sss.pgh.pa.us>
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Στις 15/9/23 22:42, ο/η Tom Lane έγραψε:
> Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> writes:
>> Thank you, I see that both systems use en_US.UTF-8 as lc_collate and
>> lc_ctype,
> Doesn't necessarily mean they interpret that the same way, though :-(
>
>> the below seems ok
>> FreeBSD :
>> postgres@[local]/dynacom=# select * from (values
>> ('a'),('Z'),('_'),('.'),('0')) as qry order by column1::text;
>> column1
>> ---------
>> _
>> .
>> 0
>> a
>> Z
>> (5 rows)
> Sadly, this proves very little about Linux's behavior.  glibc's idea
> of en_US involves some very complicated multi-pass sort rules.
> AFAICT from the FreeBSD sort(1) man page, FreeBSD defines en_US
> as "same as C except case-insensitive", whereas I'm pretty sure
> that underscores and other punctuation are nearly ignored in
> glibc's interpretation; they'll only be taken into account if the

Thank you so much. Makes perfect sense.

This begs the question asked also in the -sql list : how do I index on 
regex'es, or at least have a barely scalable solution? Here I try to 
match a given string against a stored regex, whereas in pg_trgm's case 
the user tries to match a stored text against a given regex.

> alphanumeric parts of the strings sort equal.
>
> 			regards, tom lane

-- 
Achilleas Mantzios
  IT DEV - HEAD
  IT DEPT
  Dynacom Tankers Mgmt