[2.0.x] Fixed #28702 -- Made query lookups for CIText fields use citext.

Backport of f0a68c2511 from master

django/contrib/postgres/fields/citext.py

@@ -4,6 +4,10 @@ __all__ = ['CICharField', 'CIEmailField', 'CIText', 'CITextField']
 
 
 class CIText:
+
+    def get_internal_type(self):
+        return 'CI' + super().get_internal_type()
+
     def db_type(self, connection):
         return 'citext'
 

django/db/backends/postgresql/operations.py

@@ -77,6 +77,8 @@ class DatabaseOperations(BaseDatabaseOperations):
                            'istartswith', 'endswith', 'iendswith', 'regex', 'iregex'):
             if internal_type in ('IPAddressField', 'GenericIPAddressField'):
                 lookup = "HOST(%s)"
+            elif internal_type in ('CICharField', 'CIEmailField', 'CITextField'):
+                lookup = '%s::citext'
             else:
                 lookup = "%s::text"
 

django/db/backends/postgresql/schema.py

@@ -107,11 +107,12 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
 
     def _alter_field(self, model, old_field, new_field, old_type, new_type,
                      old_db_params, new_db_params, strict=False):
-        # Drop indexes on varchar/text columns that are changing to a different
-        # type.
+        # Drop indexes on varchar/text/citext columns that are changing to a
+        # different type.
         if (old_field.db_index or old_field.unique) and (
             (old_type.startswith('varchar') and not new_type.startswith('varchar')) or
-            (old_type.startswith('text') and not new_type.startswith('text'))
+            (old_type.startswith('text') and not new_type.startswith('text')) or
+            (old_type.startswith('citext') and not new_type.startswith('citext'))
         ):
             index_name = self._create_index_name(model._meta.db_table, [old_field.column], suffix='_like')
             self.execute(self._delete_constraint_sql(self.sql_delete_index, model, index_name))

docs/releases/1.11.8.txt

@@ -24,3 +24,6 @@ Bugfixes
 
 * Fixed crash on SQLite and MySQL when ordering by a filtered subquery that
   uses ``nulls_first`` or ``nulls_last`` (:ticket:`28848`).
+
+* Made query lookups for ``CICharField``, ``CIEmailField``, and ``CITextField``
+  use a ``citext`` cast (:ticket:`28702`).

tests/backends/postgresql/tests.py

@@ -138,6 +138,10 @@ class Tests(TestCase):
         for lookup in lookups:
             with self.subTest(lookup=lookup):
                 self.assertIn('::text', do.lookup_cast(lookup))
+        for lookup in lookups:
+            for field_type in ('CICharField', 'CIEmailField', 'CITextField'):
+                with self.subTest(lookup=lookup, field_type=field_type):
+                    self.assertIn('::citext', do.lookup_cast(lookup, internal_type=field_type))
 
     def test_correct_extraction_psycopg2_version(self):
         from django.db.backends.postgresql.base import psycopg2_version

tests/postgres_tests/test_citext.py

@@ -12,6 +12,7 @@ from .models import CITestModel
 
 @modify_settings(INSTALLED_APPS={'append': 'django.contrib.postgres'})
 class CITextTestCase(PostgreSQLTestCase):
+    case_sensitive_lookups = ('contains', 'startswith', 'endswith', 'regex')
 
     @classmethod
     def setUpTestData(cls):
@@ -42,3 +43,21 @@ class CITextTestCase(PostgreSQLTestCase):
         instance = CITestModel.objects.get()
         self.assertEqual(instance.array_field, self.john.array_field)
         self.assertTrue(CITestModel.objects.filter(array_field__contains=['joe']).exists())
+
+    def test_lookups_name_char(self):
+        for lookup in self.case_sensitive_lookups:
+            with self.subTest(lookup=lookup):
+                query = {'name__{}'.format(lookup): 'john'}
+                self.assertSequenceEqual(CITestModel.objects.filter(**query), [self.john])
+
+    def test_lookups_description_text(self):
+        for lookup, string in zip(self.case_sensitive_lookups, ('average', 'average joe', 'john', 'Joe.named')):
+            with self.subTest(lookup=lookup, string=string):
+                query = {'description__{}'.format(lookup): string}
+                self.assertSequenceEqual(CITestModel.objects.filter(**query), [self.john])
+
+    def test_lookups_email(self):
+        for lookup, string in zip(self.case_sensitive_lookups, ('john', 'john', 'john.com', 'john.com')):
+            with self.subTest(lookup=lookup, string=string):
+                query = {'email__{}'.format(lookup): string}
+                self.assertSequenceEqual(CITestModel.objects.filter(**query), [self.john])