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=============================
Database migration operations
=============================
All of these :doc:`operations </ref/migration-operations>` are available from
the ``django.contrib.postgres.operations`` module.
.. _create-postgresql-extensions:
Creating extension using migrations
===================================
You can create a PostgreSQL extension in your database using a migration file.
This example creates an hstore extension, but the same principles apply for
other extensions.
Set up the hstore extension in PostgreSQL before the first ``CreateModel``
or ``AddField`` operation that involves
:class:`~django.contrib.postgres.fields.HStoreField` by adding a migration with
the :class:`~django.contrib.postgres.operations.HStoreExtension` operation.
For example::
from django.contrib.postgres.operations import HStoreExtension
class Migration(migrations.Migration):
...
operations = [
HStoreExtension(),
...
]
The operation skips adding the extension if it already exists.
For most extensions, this requires a database user with superuser privileges.
If the Django database user doesn't have the appropriate privileges, you'll
have to create the extension outside of Django migrations with a user that has
them. In that case, connect to your Django database and run the query
``CREATE EXTENSION IF NOT EXISTS hstore;``.
.. versionchanged:: 3.2
In older versions, the pre-existence of the extension isn't checked.
.. currentmodule:: django.contrib.postgres.operations
``CreateExtension``
===================
.. class:: CreateExtension(name)
An ``Operation`` subclass which installs a PostgreSQL extension. For common
extensions, use one of the more specific subclasses below.
.. attribute:: name
This is a required argument. The name of the extension to be installed.
``BloomExtension``
==================
.. class:: BloomExtension()
.. versionadded:: 3.1
Installs the ``bloom`` extension.
``BtreeGinExtension``
=====================
.. class:: BtreeGinExtension()
Installs the ``btree_gin`` extension.
``BtreeGistExtension``
======================
.. class:: BtreeGistExtension()
Installs the ``btree_gist`` extension.
``CITextExtension``
===================
.. class:: CITextExtension()
Installs the ``citext`` extension.
``CryptoExtension``
===================
.. class:: CryptoExtension()
Installs the ``pgcrypto`` extension.
``HStoreExtension``
===================
.. class:: HStoreExtension()
Installs the ``hstore`` extension and also sets up the connection to
interpret hstore data for possible use in subsequent migrations.
``TrigramExtension``
====================
.. class:: TrigramExtension()
Installs the ``pg_trgm`` extension.
``UnaccentExtension``
=====================
.. class:: UnaccentExtension()
Installs the ``unaccent`` extension.
.. _manage-postgresql-collations:
Managing collations using migrations
====================================
.. versionadded:: 3.2
If you need to filter or order a column using a particular collation that your
operating system provides but PostgreSQL does not, you can manage collations in
your database using a migration file. These collations can then be used with
the ``db_collation`` parameter on :class:`~django.db.models.CharField`,
:class:`~django.db.models.TextField`, and their subclasses.
For example, to create a collation for German phone book ordering::
from django.contrib.postgres.operations import CreateCollation
class Migration(migrations.Migration):
...
operations = [
CreateCollation(
'german_phonebook',
provider='icu',
locale='und-u-ks-level2',
),
...
]
.. class:: CreateCollation(name, locale, *, provider='libc', deterministic=True)
Creates a collation with the given ``name``, ``locale`` and ``provider``.
Set the ``deterministic`` parameter to ``False`` to create a
non-deterministic collation, such as for case-insensitive filtering.
.. class:: RemoveCollation(name, locale, *, provider='libc', deterministic=True)
Removes the collations named ``name``.
When reversed this is creating a collation with the provided ``locale``,
``provider``, and ``deterministic`` arguments. Therefore, ``locale`` is
required to make this operation reversible.
.. admonition:: Restrictions
PostgreSQL 9.6 only supports the ``'libc'`` provider.
Non-deterministic collations are supported only on PostgreSQL 12+.
Concurrent index operations
===========================
PostgreSQL supports the ``CONCURRENTLY`` option to ``CREATE INDEX`` and
``DROP INDEX`` statements to add and remove indexes without locking out writes.
This option is useful for adding or removing an index in a live production
database.
.. class:: AddIndexConcurrently(model_name, index)
Like :class:`~django.db.migrations.operations.AddIndex`, but creates an
index with the ``CONCURRENTLY`` option. This has a few caveats to be aware
of when using this option, see `the PostgreSQL documentation of building
indexes concurrently <https://www.postgresql.org/docs/current/
sql-createindex.html#SQL-CREATEINDEX-CONCURRENTLY>`_.
.. class:: RemoveIndexConcurrently(model_name, name)
Like :class:`~django.db.migrations.operations.RemoveIndex`, but removes the
index with the ``CONCURRENTLY`` option. This has a few caveats to be aware
of when using this option, see `the PostgreSQL documentation
<https://www.postgresql.org/docs/current/sql-dropindex.html>`_.
.. note::
The ``CONCURRENTLY`` option is not supported inside a transaction (see
:ref:`non-atomic migration <non-atomic-migrations>`).
|
