Indexing a field of type point

Hi,

I realise this isn't strictly an SQL question, but I figured this list might be
better suited than the general one. Please let me know if not.

I have a table containing a field named location, of type point, i.e. a
position in two dimensions. The table has several million records in, and I
need to extract those records whose location value is contained within a
certain bounding box.

To do this efficiently (rather than as a linear scan), I would like to create
an index over this field. However, using GIST under Postgresql 8.2.4 I can't do
this:

test=# create index points_location_index on points using gist (location);
ERROR: data type point has no default operator class for access method "gist"
HINT: You must specify an operator class for the index or define a default
operator class for the data type.

Looking through the available classes, there are none defined for points :-(.

I have seen a post saying that one could use
create index points_location_index on points using gist (location box_ops);
but that comes back with the error that (rightly) box_ops doesn't have
operators for data of type point.

Is anyone aware of a way of creating a suitable index? I am aware of PostGIS,
but would prefer not to have to rework a whole load of code to use the
different geometrical field types it provides.

Thanks for any help!

David.

--
David Cottingham
Computer Laboratory, University of Cambridge

http://www.cl.cam.ac.uk/users/dnc25/