==================
Installing PostGIS
==================

`PostGIS`_ adds geographic object support to PostgreSQL, turning it
into a spatial database. :ref:`geosbuild`, :ref:`proj4` and
:ref:`gdalbuild` should be installed prior to building PostGIS. You
might also need additional libraries, see `PostGIS requirements`_.

The `psycopg`_ or `psycopg2`_ module is required for use as the database
adapter when using GeoDjango with PostGIS.

On Debian/Ubuntu, you are advised to install the following packages:
``postgresql-x``, ``postgresql-x-postgis-3``, ``postgresql-server-dev-x``,
and ``python3-psycopg3`` (x matching the PostgreSQL version you want to
install). Alternately, you can `build from source`_. Consult the
platform-specific instructions if you are on :ref:`macos` or :ref:`windows`.

.. _PostGIS: https://postgis.net/
.. _psycopg: https://www.psycopg.org/psycopg3/
.. _psycopg2: https://www.psycopg.org/
.. _PostGIS requirements: https://postgis.net/docs/postgis_installation.html#install_requirements
.. _build from source: https://postgis.net/docs/postgis_installation.html#install_short_version

Post-installation
=================

.. _spatialdb_template:

Creating a spatial database
---------------------------

PostGIS includes an extension for PostgreSQL that's used to enable spatial
functionality:

.. code-block:: shell

    $ createdb  <db name>
    $ psql <db name>
    > CREATE EXTENSION postgis;

The database user must be a superuser in order to run
``CREATE EXTENSION postgis;``. The command is run during the :djadmin:`migrate`
process. An alternative is to use a migration operation in your project::

    from django.contrib.postgres.operations import CreateExtension
    from django.db import migrations


    class Migration(migrations.Migration):
        operations = [CreateExtension("postgis"), ...]

If you plan to use PostGIS raster functionality, you should also activate the
``postgis_raster`` extension. You can install the extension using the
:class:`~django.contrib.postgres.operations.CreateExtension` migration
operation, or directly by running ``CREATE EXTENSION postgis_raster;``.

GeoDjango does not currently leverage any `PostGIS topology functionality`__.
If you plan to use those features at some point, you can also install the
``postgis_topology`` extension by issuing ``CREATE EXTENSION
postgis_topology;``.

__ https://postgis.net/docs/Topology.html

Managing the database
---------------------

To administer the database, you can either use the pgAdmin III program
(:menuselection:`Start --> PostgreSQL X --> pgAdmin III`) or the SQL Shell
(:menuselection:`Start --> PostgreSQL X --> SQL Shell`). For example, to create
a ``geodjango`` spatial database and user, the following may be executed from
the SQL Shell as the ``postgres`` user:

.. code-block:: psql

    postgres# CREATE USER geodjango PASSWORD 'my_passwd';
    postgres# CREATE DATABASE geodjango OWNER geodjango;
