PostgreSQL function for haversine distance calculation, in miles

haversine.sql

-- Haversine Formula based geodistance in miles (constant is diameter of Earth in miles)
-- Based on a similar PostgreSQL function found here: https://gist.github.com/831833
-- Updated to use distance formulas found here: http://www.codecodex.com/wiki/Calculate_distance_between_two_points_on_a_globe
CREATE OR REPLACE FUNCTION public.geodistance(alat double precision, alng double precision, blat double precision, blng double precision)
  RETURNS double precision AS
$BODY$
SELECT asin(
  sqrt(
    sin(radians($3-$1)/2)^2 +
    sin(radians($4-$2)/2)^2 *
    cos(radians($1)) *
    cos(radians($3))
  )
) * 7926.3352 AS distance;
$BODY$
  LANGUAGE sql IMMUTABLE
  COST 100;

This is great! Thanks for sharing!

Thank you , that is awesome

Thank you for posting it -- really helps. FYI, https://gist.github.com/831833 link in the description is broken.

Brilliant. Thanks.

Why 7926.3352? How do I get the result in kms?

This, for example, uses 3960 and 6371!?

One question I have a problem, in my application I use this implementation to get a distance between two points:
6371 * acos(cos(radians(-22.9557306)) * cos(radians(addresses.latitude)) * cos(radians(addresses.longitude) - radians(-43.186176)) + sin(radians(-22.9557306)) * sin(radians(addresses.latitude))) as distance
But when two points are equal, this value is returned NaN
With your implementation worked for me, however in case the same points return to number like this 9.05124604553969e-13, you know that happening?

@FruitAndAShape Late to the party but Haversine requires a final multiplication by 2. 7926 is twice the radius of the earth in miles. You could switch that to 2 * 6371 = 12742 for kilometers.

@FruitAndAShape Late to the party but Haversine requires a final multiplication by 2. 7926 is twice the radius of the earth in miles. You could switch that to 2 * 6371 = 12742 for kilometers.

Thanks :)