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RE: [HACKERS] Indexing for geographic objects?

From: Franck Martin <Franck(at)sopac(dot)org>
To: "'selkovjr(at)mcs(dot)anl(dot)gov'" <selkovjr(at)mcs(dot)anl(dot)gov>
Cc: "'pgsql-general '" <pgsql-general(at)postgresql(dot)org>, "'pgsql-hackers '" <pgsql-hackers(at)postgresql(dot)org>
Subject: RE: [HACKERS] Indexing for geographic objects?
Date: 2000-11-26 23:06:21
Message-ID: F12ECEA0435AD211B5280008C7ACBC857FF043@BIGIRON (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
It seems that your code is exactly what I want.

I have already created geographical objects which contains MBR(Minimum
Bounding Rectangle) in their structure, so it is a question of rewriting
your code to change the access to the cube structure to the MBR structure
inside my geoobject. (cf http://fmaps.sourceforge.net/) Look in the CVS for
latest. I have been slack lately on the project, but I'm not forgetting it.

Quickly I ran through the code, and I think your cube is strictly speaking a
box, which also a MBR.

However I didn't see the case of intersection, which is the main question
when you want to display object that are visible inside a box.

I suppose your code is under GPL, and you have no problem for me to use it,
providing I put your name and credits somewhere.

Cheers.

Franck Martin
Database Development Officer
SOPAC South Pacific Applied Geoscience Commission
Fiji
E-mail: franck(at)sopac(dot)org
Web site: http://www.sopac.org/

This e-mail is intended for its recipients only. Do not forward this e-mail
without approval. The views expressed in this e-mail may not be necessarily
the views of SOPAC.

-----Original Message-----
From: selkovjr(at)mcs(dot)anl(dot)gov [mailto:selkovjr(at)mcs(dot)anl(dot)gov]
Sent: Saturday, 25 November 2000 8:56 
To: Franck Martin
Subject: Re: [HACKERS] Indexing for geographic objects? 

It is probably possible to hook up an extension directly with the
R-tree methods available in postgres -- if you stare at the code long
enough and figure how to use the correct strategies. I chose an easier
path years ago and I am still satisfied with the results. Check out
the GiST -- a general access method built on top of R-tree to provide
a user-friendly interface to it and to allow indexing of more abstract
types, for which straight R-tree is not directly applicable.

I have a small set of complete data types, of which a couple
illustrate the use of GiST indexing with the geometrical objects, in:

http://wit.mcs.anl.gov/~selkovjr/pg_extensions/

If you are using a pre-7.0 postrgres, grab the file contrib.tgz,
otherwise take contrib-7.0.tgz. The difference is insignificant, but
the pre-7.0 version will not fit the current schema. Unpack the source
into postgresql-*/contrib and follow instructions in the README
files. The types of interest for you will be seg and cube. You will
find pointers to the original sources and docs in the CREDITS section
of the README file. I also have a version of the original example code
in pggist-patched.tgz, but I did not check if it works with current
postgres. It should not be difficult to fix it if it doesn't -- the
recent development in the optimizer area made certain things
unnecessary.

You might want to check out a working example of the segment data type at:

http://wit.mcs.anl.gov/EMP/indexing.html

(search the page for 'KM')

I will be glad to help, but I would also recommend to send more
sophisticated questions to Joe Hellerstein, the leader of the original
postgres team that developed GiST. He was very helpful whenever I
turned to him during the early stages of my data type project.

--Gene

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