From: Stephan Szabo <sszabo@megazone.bigpanda.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Bruno Wolff III <bruno@wolff.to>
Cc: Achilleus Mantzios <achill@matrix.gatewaynet.com>
Cc: email lists <lists@darrenmackay.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: query not using index for descending records?
Date: Thu, 29 Jan 2004 10:27:57 -0800 (PST)
Message-ID: <20040129101857.D26621@megazone.bigpanda.com> (raw)
In-Reply-To: <24411.1075397054@sss.pgh.pa.us>
References: <20040129131847.GE17068@wolff.to>
<Pine.LNX.4.44.0401291525350.9854-100000@matrix.gatewaynet.com>
<20040129140655.GA14885@wolff.to>
<20040129075643.D23153@megazone.bigpanda.com>
<24411.1075397054@sss.pgh.pa.us>
On Thu, 29 Jan 2004, Tom Lane wrote:
> 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.
Yeah, that's what I figured. I thought it might be useful for people to
play with though since at least for the integer/float types writing C
versions of the comparitors is easy. I was thinking for real it'd be nice
to be able to use the normal comparitor but invert the return value as
necessary rather than providing two functions, but I didn't look at what
that would take.
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To: pgsql-sql@postgresql.org
Cc: sszabo@megazone.bigpanda.com, tgl@sss.pgh.pa.us, bruno@wolff.to, achill@matrix.gatewaynet.com, lists@darrenmackay.com
Subject: Re: query not using index for descending records?
In-Reply-To: <20040129101857.D26621@megazone.bigpanda.com>
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