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To: Stephan Szabo <sszabo@megazone.bigpanda.com>
Cc: Bruno Wolff III <bruno@wolff.to>,
	Achilleus Mantzios <achill@matrix.gatewaynet.com>,
	email lists <lists@darrenmackay.com>, pgsql-sql@postgresql.org
Subject: Re: query not using index for descending records? 
In-reply-to: <20040129075643.D23153@megazone.bigpanda.com> 
References: <20040129131847.GE17068@wolff.to>
	<Pine.LNX.4.44.0401291525350.9854-100000@matrix.gatewaynet.com>
	<20040129140655.GA14885@wolff.to>
	<20040129075643.D23153@megazone.bigpanda.com>
Comments: In-reply-to Stephan Szabo <sszabo@megazone.bigpanda.com>
	message dated "Thu, 29 Jan 2004 08:05:59 -0800"
Date: Thu, 29 Jan 2004 12:24:14 -0500
Message-ID: <24411.1075397054@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Stephan Szabo <sszabo@megazone.bigpanda.com> writes:
> I'd thought that I'd previously sent a message containing a set of
> definitions for the reverse opclasses (not meant for inclusion to the
> system because I was making SQL functions that basically did -<normal
> comparison function> to use as the function of the operator class, but
> possibly worth playing with) but now that I actually search again, I don't
> see it.

I don't recall having seen such a thing go by...

I fear that using SQL functions as comparators would only be useful for
proof-of-concept, not as an industrial-strength implementation.  The
index code needs comparator functions not to leak memory, and I doubt
that that could be guaranteed with a SQL function.  You'd probably have
speed issues too.

			regards, tom lane