Re: Missing rows with index scan when collation is not "C" (PostgreSQL 9.5)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Peter Geoghegan <pg(at)heroku(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Marc-Olaf Jaschke <marc-olaf(dot)jaschke(at)s24(dot)com>, Postgres-Bugs <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: Missing rows with index scan when collation is not "C" (PostgreSQL 9.5)
Date: 2016-03-22 23:26:15
Message-ID: 19682.1458689175@sss.pgh.pa.us
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Peter Geoghegan <pg(at)heroku(dot)com> writes:
> I now think that we have this backwards: This isn't a bug in glibc's
> strxfrm(); it's a bug in glibc's strcoll().

FWIW, the test program I just posted includes checks to see if the two
cases produce self-consistent sort orders. So far I've seen no evidence
that they don't; that is, strcoll() produces a consistent sort order,
and strxfrm() produces a consistent sort order, but not the same one.
That being the case, arguing about which one is wrong seems a bit
academic, not to mention well above my pay grade so far as the theoretical
behavior of locale-specific sort ordering is concerned.

regards, tom lane

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