PostGIS

PostGIS adds support for geographic objects in the PostgreSQL database. This document describes the process for installing PostGIS and creating a template PostGIS database. It is assumed that PostgreSQL has been installed. If it has not, please refer to the PostgreSQL page.

Installing PostGIS

Install the postgis package.

Installing PostGIS Extension

Since PostgreSQL 9.1, the preferred approach is to install PostGIS and enable postgis extension for each spatial database.

$ psql

 -- verify available extensions
 SELECT name, default_version,installed_version 
 FROM pg_available_extensions WHERE name LIKE 'postgis%' ;
 
 -- install extension for spatial database mygisdb
 \c mygisdb
 CREATE EXTENSION postgis;
 CREATE EXTENSION postgis_topology;
 CREATE EXTENSION fuzzystrmatch;
 CREATE EXTENSION postgis_tiger_geocoder;

You do not need to do the below "Creating a Template PostGIS Database" step if you use PostGIS extension.

• upgrade postgis extension

$ psql

 ALTER EXTENSION postgis UPDATE TO "2.1.0";

• migrate spatial database created with postgis_template

Dump and drop the spatial database, re-create a spatial database with extension, and restore the dumped database. Follow https://www.postgis.net/docs/postgis_installation.html#hard_upgrade for specific commands.

Creating a Template PostGIS Database

• Become the postgres user.

# su - postgres

• If you have not created a superuser for accessing PostgreSQL, you may want do that now. You will be prompted for granting permissions to that user.

$ createuser [username]

• Create a new database called "template_postgis".

$ createdb -O [username] template_postgis -E UTF-8

• Load the PostGIS spatial types for PostgreSQL and spatial reference systems. "postgis.sql" and "spatial_ref_sys.sql" are part of the installation of PostGIS, and may reside somewhere else besides "/usr/sharepostgresql/contrib/postgis-2.1/" depending on the installation. (Below is for default postgis 2.1 installation)

$ psql -d template_postgis -f /usr/share/postgresql/contrib/postgis-2.1/postgis.sql
$ psql -d template_postgis -f /usr/share/postgresql/contrib/postgis-2.1/spatial_ref_sys.sql

• Make it a real template.

$ psql

UPDATE pg_database SET datistemplate = TRUE WHERE datname = 'template_postgis';

Creating a PostGIS Database From the Template

It is common practice to reserve a bare template for creating new PostGIS databases. As a PostgreSQL superuser, the following command will create a new database:

$ createdb -T template_postgis [new_postgis_db]

More Resources

For additional resources concerning PostGIS, check out the PostGIS Documentation.

PostGIS failing with json_tokener_error

This happends when adding postgis as an extension. The libjson-c package has changed, and PostGIS has not put out a stable release with this yet. It is in 2.1.0rc1, though. The bug-report is https://trac.osgeo.org/postgis/ticket/2213

The fix is to download the postgis PKGBUILD and then change the version to '2.1.0rc1'. Do not forget to change the sha256sum.