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Re: BUG #6278: Index scans on '>' condition on field with many NULLS

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Maksym Boguk <maxim(dot)boguk(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #6278: Index scans on '>' condition on field with many NULLS
Date: 2011-10-31 19:39:57
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-bugs
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, Oct 31, 2011 at 12:43 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> A patch along these lines should be pretty localized.  Has anyone
>> got an opinion on whether to back-patch or not?  This seems like a
>> performance bug, but given the lack of prior complaints, maybe we
>> shouldn't take any risks for it.

> I think my vote would be to just fix it in master.

After researching the issue, my patch looks like the attached.  This
seems to apply cleanly back to about 8.3, so I'm inclined to back-patch
that far.  It's pretty simple, and I think the reason we (I) got it
wrong to begin with is just lack of thought about the NULLs case.

			regards, tom lane

Attachment: stop-at-nulls.patch
Description: text/x-patch (4.7 KB)

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