Improve query speed? - Mailing list pgsql-novice

Hi there,

I was wondering if anyone had any ideas on how to make this UPDATE
query any quicker please?

UPDATE stage_cleaned
SET route_geom =
(SELECT route_geom.wkb_geometry FROM route_geom WHERE
route_geom.stage_cleaned_id::text = stage_cleaned.id::text GROUP BY
stage_cleaned_id, wkb_geometry)
WHERE route_geom IS NULL;

The table 'stage_cleaned' has about 300,000 rows, and the table
route_geom has a similar number.

Thanks

James