Re: KNN-GiST with recheck

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: KNN-GiST with recheck
Date: 2015-05-13 19:16:15
Message-ID: 5553A2FF.1030501@iki.fi
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On 04/17/2015 12:05 PM, Alexander Korotkov wrote:
> On Wed, Feb 25, 2015 at 12:15 PM, Alexander Korotkov <aekorotkov(at)gmail(dot)com>
> wrote:
>
>> Hi!
>>
>> On Tue, Feb 24, 2015 at 5:39 PM, Tomas Vondra <
>> tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>>
>>> On 17.2.2015 14:21, Alexander Korotkov wrote:
>>>> On Sun, Feb 15, 2015 at 2:08 PM, Alexander Korotkov
>>>> <aekorotkov(at)gmail(dot)com <mailto:aekorotkov(at)gmail(dot)com>> wrote:
>>>>
>>>> Revised patch with reordering in GiST is attached
>>>> (knn-gist-recheck-in-gist.patch) as well as testing script (test.py).
>>>
>>> I meant to do a bit of testing on this (assuming it's still needed), but
>>> the patches need rebasing - Heikki fixed a few issues, so they don't
>>> apply cleanly.
>>>
>>
>> Both patches are revised.
>>
>
> Both patches are rebased against current master.

This looks pretty much ready. I'm going to spend some time on this on
Friday, and if all looks good, commit. (Thursday's a public holiday here).

One quick comment:

It would be good to avoid the extra comparisons of the distances, when
the index doesn't return any lossy items. As the patch stands, it adds
one extra copyDistances() call and a cmp_distances() call for each tuple
(in a knn-search), even if there are no lossy tuples.

- Heikki

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