Order by nearest - PostGIS, GeoRuby, spatial_adapter

Question

I'm trying to do an order query that finds records nearest to the current_user.

I know the distance between the two points is: current_location.euclidean_distance(@record.position)

How can I work this into a PostGIS (or active_record/spatial_adapter) query?

Answer 1

To get the 5 closest:

SELECT * FROM your_table 
ORDER BY ST_Distance(your_table.geom, ST_Geomfromtext(your point as wkt)) 
limit 5;

If you have a big dataset and know that you don't want to search further than , say 1 km, the query will be more efficient if you do:

SELECT * FROM your_table 
WHERE ST_DWithin(your_table.geom, ST_Geomfromtext(your point as wkt, 1000)
ORDER BY ST_Distance(your_table.geom, ST_Geomfromtext(your point as wkt))  
limit 5;

/Nicklas

Answer 2

Just in case somebody stumbles upon this issue in rails 4. I am using rgeo gem and this works for me

scope :closest, ->(point) { order("ST_Distance(lonlat, ST_GeomFromText('#    {point.as_text}', #{SRID}))").limit(5) }