Re: [NOVICE] WHERE clause not used when index is used

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Tobias Florek <postgres(at)ibotty(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Kevin Grittner <kgrittn(at)postgresql(dot)org>
Subject: Re: [NOVICE] WHERE clause not used when index is used
Date: 2016-03-01 17:32:48
Message-ID: 20160301173248.GE3127@tamriel.snowman.net
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* Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
> [ trimming -novice from the cc list ]
>
> Jeff Janes <jeff(dot)janes(at)gmail(dot)com> writes:
> > On Tue, Mar 1, 2016 at 7:40 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> (Problem is reproducible in 9.5 and HEAD, but not 9.4.)
>
> > Bisects down to:
>
> > 606c0123d627b37d5ac3f7c2c97cd715dde7842f is the first bad commit
> > commit 606c0123d627b37d5ac3f7c2c97cd715dde7842f
> > Author: Simon Riggs <simon(at)2ndQuadrant(dot)com>
> > Date: Tue Nov 18 10:24:55 2014 +0000
>
> > Reduce btree scan overhead for < and > strategies
>
> Hmm ... just from the commit message, this seems much more likely to be
> the cause than does the buffer locking patch Stephen fingered. Stephen,
> how'd you identify 2ed5b87f as being the problem?

Badly. :)

I didn't expect it to be something that far back and was just going
backwards through reverting/testing patches that looked like
candidates, but forgot to create the index when I tested the revert of
that, which made it look like reverting it 'fixed' it.

Apologies for the noise.

Thanks!

Stephen

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