| From: | Greg Stark <gsstark(at)mit(dot)edu> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Greg Stark <gsstark(at)mit(dot)edu>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Hannu Krosing <hannu(at)skype(dot)net>, John Hansen <john(at)geeknet(dot)com(dot)au>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Does anybody use ORDER BY x USING y? |
| Date: | 2005-09-19 16:21:00 |
| Message-ID: | 87zmq9ni4z.fsf@stark.xeocode.com |
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| Lists: | pgsql-hackers |
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> Greg Stark <gsstark(at)mit(dot)edu> writes:
> > The thing is that these opclasses you're describing are closely related. It
> > ought to be possible to use a single index to produce results in any of the
> > four orders you describe.
>
> Wrong --- only two of them. You can't magically swap nulls from one end
> of the index to the other (and Hannu's flight of fantasy about double
> indexscans is just a flight of fantasy; it would be solving the problem
> at entirely the wrong place).
I think that was my flight of fantasy. I didn't say it was pretty but it would
solve the problem. Whereas having a separate opclass would mean someone would
need a second index to satisfy the ordering which seems silly.
--
greg
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