RE: [HACKERS] Indexing for geographic objects? - Mailing list pgsql-general
From | Oleg Bartunov |
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Subject | RE: [HACKERS] Indexing for geographic objects? |
Date | |
Msg-id | Pine.GSO.3.96.SK.1001126175315.13366F-100000@ra Whole thread Raw |
In response to | RE: [HACKERS] Indexing for geographic objects? (Michael Ansley <Michael.Ansley@intec-telecom-systems.com>) |
Responses |
Re: [HACKERS] Indexing for geographic objects?
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List | pgsql-general |
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.Ansley@intec-telecom-systems.com> > To: 'Tom Lane ' <tgl@sss.pgh.pa.us>, 'Franck Martin ' <franck@sopac.org> > Cc: 'pgsql-general ' <pgsql-general@postgresql.org>, > 'pgsql-hackers ' <pgsql-hackers@postgresql.org>, > "'t.h.p.ansley@durham.co.uk'" <t.h.p.ansley@durham.co.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@sopac.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 > > > ********************************************************************** > This email and any files transmitted with it are confidential and > intended solely for the use of the individual or entity to whom they > are addressed. If you have received this email in error please notify > the system manager. > > This footnote also confirms that this email message has been swept by > MIMEsweeper for the presence of computer viruses. > > www.mimesweeper.com > ********************************************************************** > _____________________________________________________________ Oleg Bartunov, sci.researcher, hostmaster of AstroNet, Sternberg Astronomical Institute, Moscow University (Russia) Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/ phone: +007(095)939-16-83, +007(095)939-23-83
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