Re: Yet another fast GiST build

From: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
To: Darafei "Komяpa" Praliaskouski <me(at)komzpa(dot)net>
Cc: "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru>, Pavel Borisov <pashkin(dot)elfe(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Yet another fast GiST build
Date: 2020-09-09 15:39:41
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On 09/09/2020 15:20, Darafei "Komяpa" Praliaskouski wrote:
> On Wed, Sep 9, 2020 at 3:09 PM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>> Come to think of it, the point z-order comparator could benefit a lot
>> from key abbreviation, too. You could do the point -> zorder conversion
>> in the abbreviation routine.
> That's how it works in PostGIS, only that we moved to more
> effecient Hilbert curve:

Thanks, that's interesting.

I implemented the abbreviated keys for the point opclass, too, and
noticed that the patch as it was never used it. I reworked the patch so
that tuplesort_begin_index_gist() is responsible for looking up the
sortsupport function, like tuplesort_begin_index_btree() does, and uses
abbreviation when possible.

I think this is pretty much ready for commit now. I'll do a bit more
testing (do we have regression test coverage for this?), also on a
SIZEOF_DATUM==4 system since the abbreviation works differently with
that, and push if nothing new comes up. And clarify the documentation
and/or comments that the sortsupport function sees "compressed" values.

I wonder if we could use sorting to also speed up building tsvector
indexes? The values stored there are bit signatures, what would be a
good sort order for those?

- Heikki

Attachment Content-Type Size
v17-0001-Add-sort-support-for-point-gist_point_sortsuppor.patch text/x-patch 44.9 KB

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