RE: [HACKERS] Indexing for geographic objects?

I'm also interested in GiST and would be happy if somebody could provide
workable example. I have an idea to use GiST indices for our fulltextsearch
system.

Regards,

Oleg
On Sun, 26 Nov 2000, Michael Ansley wrote:

> Date: Sun, 26 Nov 2000 11:34:16 -0000
> From: Michael Ansley <Michael(dot)Ansley(at)intec-telecom-systems(dot)com>
> To: 'Tom Lane ' <tgl(at)sss(dot)pgh(dot)pa(dot)us>, 'Franck Martin ' <franck(at)sopac(dot)org>
> Cc: 'pgsql-general ' <pgsql-general(at)postgresql(dot)org>,
> 'pgsql-hackers ' <pgsql-hackers(at)postgresql(dot)org>,
> "'t(dot)h(dot)p(dot)ansley(at)durham(dot)co(dot)uk'" <t(dot)h(dot)p(dot)ansley(at)durham(dot)co(dot)uk>
> Subject: RE: [HACKERS] Indexing for geographic objects?
>
> Hi,
>
> Remember also that the GiST library has been integrated into PG, (my brother
> is doing some thesis workon that at the moment), and you can create new
> index types relatively quickly (assuming that you understand the indexing
> theory ;-) using this mechanism. Run a web search on GiST for more info.
>
> Currently GiST has support for btree and rtree indexes, and possibly r+ or *
> trees, I can't remember which, if any, and IIRC, at least a couple more.
> However, if you have a requirement or 3d indexing, and you have the
> knowledge available, you should be able to hack a few 3d indexes together
> quite quickly.
>
>
> Cheers...
>
>
> -----Original Message-----
> From: Tom Lane
> To: Franck Martin
> Cc: pgsql-general; pgsql-hackers
> Sent: 11-26-00 4:35 AM
> Subject: Re: [HACKERS] Indexing for geographic objects?
>
> Franck Martin <franck(at)sopac(dot)org> writes:
> > I would greatly appreciate if someone could guide me through the
> > methodology to build an index for a custom type or point me to some
> > readings where the algorithm is explained (web, book, etc...).
>
> The Programmer's Guide chapter "Interfacing Extensions To Indices"
> outlines the procedure for making a new datatype indexable. It
> only discusses the case of adding btree support for a new type,
> though. For other index classes such as R-tree there are different
> sets of required operators, which are not as well documented but
> you can find out by looking at code for the already-supported
> datatypes.
>
> > I plan to use 3D geographical objects...
>
> That's a bit hard since we don't have any indexes suitable for 3-D
> coordinates --- the existing R-tree type is for 2-D objects. What's
> more it assumes that coordinates are Euclidean, which is probably
> not the model you want for geographical coordinates.
>
> In theory you could build a new index type suitable for indexing
> 3-D points, using the R-tree code as a starting point. I wouldn't
> class it as a project suitable for a newbie however :-(.
>
> Depending on what your needs are, you might be able to get by with
> projecting your objects into a flat 2-D coordinate system and using
> an R-tree index in that space. It'd just be approximate but that
> might be close enough for index purposes.
>
> regards, tom lane
>
>
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_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83