earthdistance.sql

PostgreSQL 8.2中增加了很多企业用户所需要的功能和性能上的提高,其开发团队说,该版本将加速更多企业向该数据库移植.核心开发成员之一Bruce Momjian表示,在新版PostgreSQL

-- Adjust this setting to control where the objects get created.
SET search_path = public;

-- The earth functions rely on contrib/cube having been installed and loaded.

-- earth() returns the radius of the earth in meters. This is the only
-- place you need to change things for the cube base distance functions
-- in order to use different units (or a better value for the Earth's radius).

CREATE OR REPLACE FUNCTION earth() RETURNS float8
LANGUAGE SQL IMMUTABLE
AS 'SELECT ''6378168''::float8';

-- Astromers may want to change the earth function so that distances will be
-- returned in degrees. To do this comment out the above definition and
-- uncomment the one below. Note that doing this will break the regression
-- tests.
--
-- CREATE OR REPLACE FUNCTION earth() RETURNS float8
-- LANGUAGE SQL IMMUTABLE
-- AS 'SELECT 180/pi()';

-- Define domain for locations on the surface of the earth using a cube
-- datatype with constraints. cube provides 3D indexing.
-- The cube is restricted to be a point, no more than 3 dimensions
-- (for less than 3 dimensions 0 is assumed for the missing coordinates)
-- and that the point must be very near the surface of the sphere
-- centered about the origin with the radius of the earth.

CREATE DOMAIN earth AS cube
  CONSTRAINT not_point check(cube_is_point(value))
  CONSTRAINT not_3d check(cube_dim(value) <= 3)
  CONSTRAINT on_surface check(abs(cube_distance(value, '(0)'::cube) /
  earth() - 1) < '10e-7'::float8);

CREATE OR REPLACE FUNCTION sec_to_gc(float8) 
RETURNS float8
LANGUAGE SQL
IMMUTABLE STRICT
AS 'SELECT CASE WHEN $1 < 0 THEN 0::float8 WHEN $1/(2*earth()) > 1 THEN pi()*earth() ELSE 2*earth()*asin($1/(2*earth())) END';

CREATE OR REPLACE FUNCTION gc_to_sec(float8)
RETURNS float8
LANGUAGE SQL
IMMUTABLE STRICT
AS 'SELECT CASE WHEN $1 < 0 THEN 0::float8 WHEN $1/earth() > pi() THEN 2*earth() ELSE 2*earth()*sin($1/(2*earth())) END';

CREATE OR REPLACE FUNCTION ll_to_earth(float8, float8)
RETURNS earth
LANGUAGE SQL
IMMUTABLE STRICT
AS 'SELECT cube(cube(cube(earth()*cos(radians($1))*cos(radians($2))),earth()*cos(radians($1))*sin(radians($2))),earth()*sin(radians($1)))::earth';

CREATE OR REPLACE FUNCTION latitude(earth)
RETURNS float8
LANGUAGE SQL
IMMUTABLE STRICT
AS 'SELECT CASE WHEN cube_ll_coord($1, 3)/earth() < -1 THEN -90::float8 WHEN cube_ll_coord($1, 3)/earth() > 1 THEN 90::float8 ELSE degrees(asin(cube_ll_coord($1, 3)/earth())) END';

CREATE OR REPLACE FUNCTION longitude(earth)
RETURNS float8
LANGUAGE SQL
IMMUTABLE STRICT
AS 'SELECT degrees(atan2(cube_ll_coord($1, 2), cube_ll_coord($1, 1)))';

CREATE OR REPLACE FUNCTION earth_distance(earth, earth)
RETURNS float8
LANGUAGE SQL
IMMUTABLE STRICT
AS 'SELECT sec_to_gc(cube_distance($1, $2))';

CREATE OR REPLACE FUNCTION earth_box(earth, float8)
RETURNS cube
LANGUAGE SQL
IMMUTABLE STRICT
AS 'SELECT cube_enlarge($1, gc_to_sec($2), 3)';
  
--------------- geo_distance

CREATE OR REPLACE FUNCTION geo_distance (point, point)
RETURNS float8
LANGUAGE C IMMUTABLE STRICT AS '$libdir/earthdistance';

--------------- geo_distance as operator <@>

CREATE OPERATOR <@> (
  LEFTARG = point,
  RIGHTARG = point,
  PROCEDURE = geo_distance,
  COMMUTATOR = <@>
);