So close... It is a testament to my blockheadedness that I had not considered that (Dave probably did). Here is the standards-mandated definition of the table:

CREATE TABLE GEOMETRY_COLUMNS (
F_TABLE_CATALOG VARCHAR(256) NOT NULL,
F_TABLE_SCHEMA VARCHAR(256) NOT NULL,
F_TABLE_NAME VARCHAR(256) NOT NULL,
F_GEOMETRY_COLUMN VARCHAR(256) NOT NULL,
COORD_DIMENSION INTEGER,
SRID INTEGER REFERENCES SPATIAL_REF_SYS,
CONSTRAINT GC_PK PRIMARY KEY
(F_TABLE_CATALOG, F_TABLE_SCHEMA, F_TABLE_NAME, F_GEOMETRY_COLUMN)
)

Everything except for COORD_DIMENSION and SRID could be extracted from the pg_class table as a view, which would be nice. The COORD_DIMENSION is just the dimensionality of the geometries, and the SRID is the spatial reference system identifier, which is a key into another mandated OpenGIS table, 'SPATIAL_REF_SYS'.

Now, if we changed the geometry type so that when one defined a geometry column, one had to include info about what SRID and what dimension it was, (ala varchar(243)) maybe the whole schmeer could reside in pg_class and geometry_columns would be a trivial view?

Crazy? Loony?

P.

Tom Lane wrote:
Paul Ramsey <[EMAIL PROTECTED]> writes:

We have a similar requirement for PostGIS.
In order to meet the OpenGIS specification, we have to maintain a GEOMETRY_COLUMNS table which includes an entry for every column in the db which holds a spatial column. It would be ideal if we could have triggers run on CREATE TABLE, DROP TABLE, and ALTER TABLE to watch for the comings and goings of spatial columns and update GEOMETRY_COLUMNS appropriately.


Couldn't you define GEOMETRY_COLUMNS as a view?  Seems a lot more
efficient than firing random triggers on every table operation.

			regards, tom lane


--
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     /
     | Paul Ramsey
     | Refractions Research
     | Email: [EMAIL PROTECTED]
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