I am using PostGIS/Tiger and I would like to find all locations within ~2 miles (~3218 meters) of a given location.
The location in question is obtained by just doing
select geography(the_geom) FROM tract WHERE tract_id = 'x'
So putting this query all together, we get:
SELECT tract_id FROM tract, (SELECT geography(the_geom) FROM tract WHERE tract_id = '36047055600') AS c(x) WHERE ST_DWithin(c.x, geography(the_geom), 3218)
So I'm using ST_DWithin to find all the neighbors.
My query works great but is taking 14 seconds. I put an index on 'the_geom' column in my tract table, but it doesn't seem to help.
How can I improve my query?