Question

I have about 2 million records in a table in PostgreSQL database with columns such as “source_location”, “destination_location”, “source_lat”,”source_long”,”destination_lat”,”destination_long” etc.

How do I make use of this table to convert it into Spatial table in PostGIS so that I can fire spatial queries on this data?

Answer 1

Let’s assume that your data is in the table foo. First add geometry columns:

SELECT AddGeometryColumn('foo', 'source_geom', 4326, 'POINT', 2);
SELECT AddGeometryColumn('foo', 'destination_geom', 4326, 'POINT', 2);

Than you can set values of geometry columns:

UPDATE foo SET
  source_geom =
    ST_SetSRID(ST_MakePoint(source_lon, source_lat), 4326),
  destination_geom = 
    ST_SetSRID(ST_MakePoint(destination_lon, destination_lat), 4326);

As a result you can use columns source_geom and destination_geom in spatial queries:

SELECT * FROM foo
WHERE ST_Distance_Sphere(source_geom, destination_geom) > 1000000;

This query returns all records where distance between source and destination > 1000 kilometers.