[postgis-users] FW: [Psycopg] RELEASE: GeoTypes-0.2.0a1

Norman Vine nhv at cape.com
Wed Sep 24 17:01:53 PDT 2003


> -----Original Message-----
> From: psycopg-bounces at lamu.initd.org
> [mailto:psycopg-bounces at lamu.initd.org]On Behalf Of Richard Taylor
> Sent: Wednesday, September 24, 2003 10:47 AM
> To: psycopg at lamu.initd.org
> Subject: [Psycopg] RELEASE: GeoTypes-0.2.0a1
> Hash: SHA1
> I have just put up the beginnings of an implementation of the OpenGIS types as 
> an extension to the GeoTypes package.
> I have the type registration working and an implementation of the Point type 
> (called OGPoint). Skeletons of the rest of the class hierachy are there as 
> well but are empty at present.
> For those that are interested in having an early look and influencing the 
> implementation you can download it from here:
> 	 http://people.initd.org/rjt/GeoTypes-0.2.0a1.tar.gz
> There are a couple of things that are worth noting and discussing:
> 1) I have named all the OpenGIS classes with a OG prefix, so Point is OGPoint 
> and Geometry is OGGeometry etc. I don't like this very much but there are 
> name clashes between the standard Postgresql geometric types and the OpenGIS 
> ones and I wanted to keep a single package. Does anyone have any other 
> suggestions as to how to deal with this?
> 2) All the OpenGIS types (there are seven of them) have the same type oid. 
> They are implemented as subclasses of the same (GEOMETRY) base class. To deal 
> with this I have registered a factory class against the type oid and the 
> factory class works out, from the string returned by the database, which 
> subclass to create. This looked like a reasonable design to me, does anyone 
> have any other suggestions?
> 3) Because the Geometry type is added to postgres on a database by database 
> basis its type oid is different for each database. I dynamically work out 
> what the type oid is by creating a table with a Geometry field and querying 
> the oid of that field. I have a feeling that I should be able to get the type 
> oid without creating the table. Does anyone know how to do this?
> Enjoy
> Richard
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