Fixed #24031 -- Added CASE expressions to the ORM.

1 files changed, 12 insertions, 0 deletions

diff --git a/django/db/backends/postgresql_psycopg2/operations.py b/django/db/backends/postgresql_psycopg2/operations.py
index 9d5b10d01a..31cbe5919f 100644
--- a/django/db/backends/postgresql_psycopg2/operations.py
+++ b/django/db/backends/postgresql_psycopg2/operations.py
@@ -5,6 +5,18 @@ from django.db.backends import BaseDatabaseOperations
 
 
 class DatabaseOperations(BaseDatabaseOperations):
+    def unification_cast_sql(self, output_field):
+        internal_type = output_field.get_internal_type()
+        if internal_type in ("GenericIPAddressField", "IPAddressField", "TimeField", "UUIDField"):
+            # PostgreSQL will resolve a union as type 'text' if input types are
+            # 'unknown'.
+            # http://www.postgresql.org/docs/9.4/static/typeconv-union-case.html
+            # These fields cannot be implicitly cast back in the default
+            # PostgreSQL configuration so we need to explicitly cast them.
+            # We must also remove components of the type within brackets:
+            # varchar(255) -> varchar.
+            return 'CAST(%%s AS %s)' % output_field.db_type(self.connection).split('(')[0]
+        return '%s'
 
     def date_extract_sql(self, lookup_type, field_name):
         # http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT