Message-ID: <55B09964.80707@iki.fi>
Date: Thu, 23 Jul 2015 10:36:04 +0300
From: Heikki Linnakangas <hlinnaka@iki.fi>
Reply-To: hlinnaka@iki.fi
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To: Paul Ramsey <pramsey@cleverelephant.ca>
CC: Teodor Sigaev <teodor@sigaev.ru>,
 Pgsql Hackers <pgsql-hackers@postgresql.org>
Subject: Re: compress method for spgist - 2
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On 03/04/2015 06:58 PM, Paul Ramsey wrote:
> On Wed, Feb 25, 2015 at 6:13 AM, Heikki Linnakangas
> <hlinnakangas@vmware.com> wrote:
>> In the original post on this, you mentioned that the PostGIS guys planned to
>> use this to store polygons, as bounding boxes
>> (http://www.postgresql.org/message-id/5447B3FF.2080406@sigaev.ru). Any idea
>> how would that work?
>
> Poorly, by hanging boxes that straddled dividing lines off the parent
> node in a big linear list. The hope would be that the case was
> sufficiently rare compared to the overall volume of data, to not be an
> issue. Oddly enough this big hammer has worked in other
> implementations at least passable well
> (https://github.com/mapserver/mapserver/blob/branch-7-0/maptree.c#L261)

Ok, I see, but that's not really what I was wondering. My question is 
this: SP-GiST partitions the space into non-overlapping sections. How 
can you store polygons - which can overlap - in an SP-GiST index? And 
how does the compress method help with that?

- Heikki


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