doc-exports/docs/dws/dev/dws_04_0304.html

Using PostGIS

• The third-party software that the PostGIS Extension depends on needs to be installed separately. If you need to use PostGIS, submit a service ticket or contact technical support to submit an application.
• If the error message "ERROR: EXTENSION is not yet supported." is displayed, the PostGIS software package is not installed. Contact technical support.

Creating PostGIS Extension

Run the CREATE EXTENSION command to create PostGIS Extension.

1	CREATE EXTENSION postgis;

Using PostGIS Extension

Use the following function to invoke a PostGIS Extension:

1	SELECT GisFunction (Param1, Param2,......);

GisFunction is the function, and Param1 and Param2 are function parameters. The following SQL statements are a simple illustration for PostGIS use. For details about related functions, see PostGIS 2.4.2 Manual.

Example 1: Create a geometry table.

1 2	CREATE TABLE cities ( id integer, city_name varchar(50) ); SELECT AddGeometryColumn('cities', 'position', 4326, 'POINT', 2);

Example 2: Insert geometry data.

1 2 3

INSERT INTO cities (id, position, city_name) VALUES (1,ST_GeomFromText('POINT(-9.5 23)',4326),'CityA'); INSERT INTO cities (id, position, city_name) VALUES (2,ST_GeomFromText('POINT(-10.6 40.3)',4326),'CityB'); INSERT INTO cities (id, position, city_name) VALUES (3,ST_GeomFromText('POINT(20.8 30.3)',4326), 'CityC');

Example 3: Calculate the distance between any two cities among three cities.

1	SELECT p1.city_name,p2.city_name,ST_Distance(p1.position,p2.position) FROM cities AS p1, cities AS p2 WHERE p1.id > p2.id;

Deleting PostGIS Extension

Run the following command to delete PostGIS Extension from GaussDB(DWS):

1	DROP EXTENSION postgis [CASCADE];

If PostGIS Extension is the dependee of other objects (for example, geometry tables), you need to add the CASCADE keyword to delete all these objects.

Parent topic: PostGIS Extension