Fixed #23423 -- Added unaccent lookup in django.contrib.postgres

docs/ref/contrib/postgres/index.txt

@@ -26,5 +26,6 @@ a number of PostgreSQL specific data types.
 
     fields
     forms
+    lookups
     operations
     validators

docs/ref/contrib/postgres/lookups.txt

@@ -0,0 +1,36 @@
+===========================
+PostgreSQL specific lookups
+===========================
+
+Unaccent
+========
+
+.. fieldlookup:: unaccent
+
+The ``unaccent`` lookup allows you to perform accent-insensitive lookups using
+a dedicated PostgreSQL extension.
+
+This lookup is implemented using :class:`~django.db.models.Transform`, so it
+can be chained with other lookup functions. To use it, you need to add
+``'django.contrib.postgres'`` in your :setting:`INSTALLED_APPS` and activate
+the `unaccent extension on PostgreSQL`_. The
+:class:`~django.contrib.postgres.operations.UnaccentExtension` migration
+operation is available if you want to perform this activation using migrations).
+
+.. _unaccent extension on PostgreSQL: http://www.postgresql.org/docs/current/interactive/unaccent.html
+
+The ``unaccent`` lookup can be used on
+:class:`~django.db.models.CharField` and :class:`~django.db.models.TextField`::
+
+    >>> City.objects.filter(name__unaccent="México")
+    ['<City: Mexico>']
+
+    >>> User.objects.filter(first_name__unaccent__startswith="Jerem")
+    ['<User: Jeremy>', '<User: Jérémy>', '<User: Jérémie>', '<User: Jeremie>']
+
+.. warning::
+
+    ``unaccent`` lookups should perform fine in most use cases. However, queries
+    using this filter will generally perform full table scans, which can be slow
+    on large tables. In those cases, using dedicated full text indexing tools
+    might be appropriate.

docs/ref/contrib/postgres/operations.txt

@@ -25,3 +25,11 @@ HStoreExtension
     A subclass of :class:`~django.contrib.postgres.operations.CreateExtension`
     which will install the ``hstore`` extension and also immediately set up the
     connection to interpret hstore data.
+
+UnaccentExtension
+-----------------
+
+.. class:: UnaccentExtension()
+
+    A subclass of :class:`~django.contrib.postgres.operations.CreateExtension`
+    which will install the ``unaccent`` extension.