Re: Hmm, nodeUnique doesn't really support backwards scan too well - Mailing list pgsql-bugs

From Tom Lane
Subject Re: Hmm, nodeUnique doesn't really support backwards scan too well
Date
Msg-id 17431.1218051436@sss.pgh.pa.us
Whole thread Raw
In response to Re: Hmm, nodeUnique doesn't really support backwards scan too well  (Gregory Stark <stark@enterprisedb.com>)
Responses Re: Hmm, nodeUnique doesn't really support backwards scan too well
List pgsql-bugs
Gregory Stark <stark@enterprisedb.com> writes:
> "Tom Lane" <tgl@sss.pgh.pa.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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