Re: Hmm, nodeUnique doesn't really support backwards scan too well

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Gregory Stark <stark(at)enterprisedb(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Hmm, nodeUnique doesn't really support backwards scan too well
Date: 2008-08-06 19:37:16
Message-ID: 17431.1218051436@sss.pgh.pa.us
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Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>> ... I'm not even sure how to fix it (the nasty case is
>> changing directions partway through the scan); let alone how to fix it in a
>> way that's obviously enough right to make me feel comfortable in
>> back-patching.

> It seems like the obvious fix is to just reverse the behaviour -- keep
> reading backwards until you see the level break then return the
> previous record from a second slot.

Well, if you think it's easy, the best form of criticism is a patch.
The change-of-direction problem seems to me to be messy --- not
insoluble, but messy enough to need beta testing.

regards, tom lane

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