X-Original-To: pgsql-hackers-postgresql.org@localhost.postgresql.org
Received: from localhost (av.hub.org [200.46.204.144])
	by postgresql.org (Postfix) with ESMTP id 8D1769DC87E;
	Fri, 17 Feb 2006 06:13:47 -0400 (AST)
Received: from postgresql.org ([200.46.204.71])
	by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024)
	with ESMTP id 83976-09; Fri, 17 Feb 2006 06:13:49 -0400 (AST)
X-Greylist: from auto-whitelisted by SQLgrey-
X-Greylist: from auto-whitelisted by SQLgrey-
Received: from moutng.kundenserver.de (moutng.kundenserver.de
	[212.227.126.188])
	by postgresql.org (Postfix) with ESMTP id 544C89DC863;
	Fri, 17 Feb 2006 06:13:44 -0400 (AST)
Received: from [84.157.11.200] (helo=lunix.schabi.de)
	by mrelayeu.kundenserver.de (node=mrelayeu7) with ESMTP (Nemesis),
	id 0ML2Dk-1FA2cR10aY-0000lN; Fri, 17 Feb 2006 11:13:46 +0100
Received: from [127.0.0.1] (localhost [127.0.0.1])
	by lunix.schabi.de (Postfix) with ESMTP id 6311A1495C8;
	Fri, 17 Feb 2006 11:13:41 +0100 (CET)
Message-ID: <43F5A1D5.20903@logix-tt.com>
Date: Fri, 17 Feb 2006 11:13:41 +0100
From: Markus Schaber <schabi@logix-tt.com>
User-Agent: Mozilla Thunderbird 1.0.7 (X11/20051017)
X-Accept-Language: de-DE, de, en-us, en
MIME-Version: 1.0
To: pgsql-performance@postgresql.org
CC: pgsql-hackers@postgresql.org
Subject: Re: qsort again (was Re: [PERFORM] Strange Create Index
References: <43F38867.6010701@gpdnet.co.uk> <19510.1140036968@sss.pgh.pa.us>
	<19779.1140038874@sss.pgh.pa.us> <43F39E53.1020009@gpdnet.co.uk>
	<20781.1140046109@sss.pgh.pa.us>
	<7.0.1.0.2.20060215194635.03b55da0@earthlink.net>
	<21615.1140052893@sss.pgh.pa.us>
	<7.0.1.0.2.20060215223710.03a7c618@earthlink.net>
	<20060216113522.GA3461@uio.no>
	<7.0.1.0.2.20060216071053.0385a1a8@earthlink.net>
	<43F481CD.2010509@logix-tt.com> <43F4A7D8.4050907@modgraph-usa.com>
	<29277.1140110108@sss.pgh.pa.us>
	<1140128256.9076.254.camel@archimedes>
	<43F4FDCC.2000204@logix-tt.com> <871wy23okp.fsf@stark.xeocode.com>
	<1140132189.9076.261.camel@archimedes>
	<Pine.LNX.4.62.0602162131211.20790@qnivq.ynat.uz>
In-Reply-To: <Pine.LNX.4.62.0602162131211.20790@qnivq.ynat.uz>
X-Enigmail-Version: 0.93.0.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Provags-ID: kundenserver.de abuse@kundenserver.de
	login:a9554655f07a4e401310f2acfb43f5bf
X-Virus-Scanned: by amavisd-new at hub.org
X-Spam-Status: No, score=0.125 required=5 tests=[AWL=0.125]
X-Spam-Score: 0.125
X-Spam-Level: 
X-Archive-Number: 200602/655
X-Sequence-Number: 79793

Hi, David,

David Lang schrieb:

>> In SQL_ASCII, just take the first 4 characters (or 8, if using a 64-bit
>> sortKey as elsewhere suggested).  The sorting key doesn't need to be a
>> one-to-one mapping.

> that would violate your second contraint ( f(a)==f(b) iff (a==b) )

no, it doesn't.

When both strings are equal, then the first characters are equal, too.

If they are not equal, the constraint condition does not match.

The first characters of the strings may be equal as f(a) may be equal to
f(b) as to the other constraint.

Markus