Subject: Re: BUG #15285: Query used index over field with ICU collation in
 some cases wrongly return 0 rows
To: Daniel Verite <daniel@manitou-mail.org>,
 Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
References: <8b6f61c4-eb21-484c-bdc6-e4b8e9f3ee62@manitou-mail.org>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, Peter Geoghegan
 <pg@bowt.ie>, =?UTF-8?B?0KDQvtC80LDQvSDQm9C40YLQvtCy0YfQtdC90LrQvg==?=
 <roman.lytovchenko@gmail.com>,
 PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Organization: 2ndQuadrant
Message-ID: <0df88ec9-90c6-54cb-ca63-7aafa5903b0c@2ndquadrant.com>
Date: Thu, 3 Sep 2020 10:26:03 +0200
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On 2020-09-03 09:41, Daniel Verite wrote:
> 	Jehan-Guillaume de Rorthais wrote:
> 
>> Maybe Daniel has some more experience feedback with other customizations
> 
> No, I've just tried various other reorderings, and didn't find any other that
> seems to have the same bug as latn-digit.
> My tests consisted of indexing a large corpus of text and running the
> index through amcheck.

In this case I'm tempted to just leave it alone and write it off as a 
bug in ICU.  We could potentially inspect the collator object at CREATE 
COLLATION time and issues warnings if we find something we know to be buggy.

I don't think we want to make our code uglier and slower for normal uses 
to work around a bug in some niche feature in ICU.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services