Kevin Neufeld wrote:
Actually Lee, addgeometrycolumn does three things. Two, as you
mentioned, and three, it adds constraints to your table so that all
geometries in your column have the same srid and are of the same
dimension and geometry type.
The function Stephen mentioned does exist, but it's called
probe_geometry_columns(). Unfortunately, it's not in the docs.
postgis=# \df *probe*
List of functions
Schema | Name | Result data type | Argument data types
--------+------------------------+------------------+---------------------
public | probe_geometry_columns | text |
(1 row)
Thank you for the correction. I shot that post off as I was running out
the door for a meeting, and didn't check the details.
I have always thought that the requirement for the geometry_columns
table was a little weird, but hey I wasn't asked when it was
implemented :) and I didn't do any of the work so I don't really have
anything to complain about. That said, it would be nice is this was
built and maintained totally transparently to the user and/or method of
creation/removal of a column. I guess this would require closer
integration with the pg_catalog and triggers on it or something like
that if that is even possible. I have not really looked into it, because
things just work most of the time.
-Steve
This function was written quite some time ago, and in my opinion, only
partially works. It adds missing entries to the geometry_columns table
by scanning the system tables for the three above mentioned constraints.
In other words, if the three constraints don't live on your new
geometry table, it won't add an entry to the geometry_columns table.
Further, this function does not remove obsolete entries from the
geometry_columns table.
I wrote my own function that truncates and repopulates the
geometry_columns table by scanning the system tables for columns of type
'geometry', rather than looking for existing constraints. It tries to
add the constraints to the table the geometry is in (sending you a
warning if it failed), and inserts a row in the geometry_column table. I
suppose one of these days, I should add it to the postgis source.
Cheers,
Kevin
Lee Hachadoorian wrote:
Andreas,
AddGeometryColumn does two things: it adds a column of type geometry,
and it adds a row to table geometry_columns. If I understand what it
is you want to do, you can do the SELECT and then add the row to
geometry_columns with an INSERT statement:
INSERT INTO public.geometry_columns
VALUES
('',<schema_name>,<table_name>,<column_name>,<dimension>,<srid>,<type>);
where the arguments use the same values you would use for the
AddGeometryColumn function.
Stephen, I don't see anything about a probegeometrycolumns( ) function
in the PostGIS docs. Can you point me in the right direction?
Thanks,
Lee Hachadoorian
PhD Student, Geography
Program in Earth & Environmental Sciences
CUNY Graduate Center
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