To: Robert Haas <robertmhaas@gmail.com>
cc: mark <dvlhntr@gmail.com>,
	Gabriele Bartolini <gabriele.bartolini@2ndquadrant.it>,
	pgsql-admin@postgresql.org, pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] locales and encodings Oh MY! 
In-reply-to: <AANLkTinNMd9C50JbvNW3qS+DjMMcLy_raYkaPExcTHYZ@mail.gmail.com> 
References: <000001cb8211$c4c91b00$4e5b5100$@com>
	<4CDCF083.2040004@2ndQuadrant.it>
	<AANLkTim-gz8BP=peGZBANVZk1S0he_0SAMoLdYAT_Rps@mail.gmail.com>
	<AANLkTinNMd9C50JbvNW3qS+DjMMcLy_raYkaPExcTHYZ@mail.gmail.com>
Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Fri, 12 Nov 2010 13:53:40 -0500"
Date: Fri, 12 Nov 2010 14:03:53 -0500
Message-ID: <14524.1289588633@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Robert Haas <robertmhaas@gmail.com> writes:
>> With how similar straight C and en_US.UTF8 are it was suggested to me,
>> by persons who are far more C knowledgeable then I in my office, that
>> this is something the PG community could "fix" . A "fix" being so that
>> "col LIKE 'foo%' " could use btree indexes in locales like en_US.UTF8
>> (and probably some others).

>> is the request unreasonable ? anyone got any idea of the price tag to
>> make that happen ?

> I thought it already did that.

No, and the odds of it ever happening are insignificant.  The sort order
associated with en_US (and other "dictionary order" locales) is just too
randomly different from what you need to optimize a LIKE search.
(Whoever told you en_US sorts similarly to C is nuts.)

The solution if you want the database's prevailing sort order to be en_US
is to put an extra text_pattern_ops index on the column you want to do
LIKE searches on.  We might eventually have the ability to spell that
"put a C-locale index on the column", but text_pattern_ops is the way to
do it today.

			regards, tom lane