Add support for SQL Variant fields

mssql/base.py

@@ -39,7 +39,7 @@
 from .client import DatabaseClient  # noqa
 from .creation import DatabaseCreation  # noqa
 from .features import DatabaseFeatures  # noqa
-from .introspection import DatabaseIntrospection, SQL_TIMESTAMP_WITH_TIMEZONE  # noqa
+from .introspection import DatabaseIntrospection, SQL_TIMESTAMP_WITH_TIMEZONE, SQL_VARIANT  # noqa
 from .operations import DatabaseOperations  # noqa
 from .schema import DatabaseSchemaEditor  # noqa
 
@@ -83,6 +83,9 @@ def encode_value(v):
         return '{%s}' % (v.replace('}', '}}'),)
     return v
 
+def handle_sql_variant_as_string(value):
+    # SQL variant of type 150 is not supported, convert it to string and return
+    return value.decode('utf-16le')
 
 def handle_datetimeoffset(dto_value):
     # Decode bytes returned from SQL Server
@@ -381,6 +384,10 @@ def get_new_connection(self, conn_params):
         # Handling values from DATETIMEOFFSET columns
         # source: https://github.com/mkleehammer/pyodbc/wiki/Using-an-Output-Converter-function
         conn.add_output_converter(SQL_TIMESTAMP_WITH_TIMEZONE, handle_datetimeoffset)
+
+        # add support for sql_variant fields
+        conn.add_output_converter(SQL_VARIANT, handle_sql_variant_as_string)
+
         conn.timeout = query_timeout
         if setencoding:
             for entry in setencoding:

mssql/introspection.py

@@ -17,6 +17,7 @@
 SQL_BIGAUTOFIELD = -777444
 SQL_SMALLAUTOFIELD = -777333
 SQL_TIMESTAMP_WITH_TIMEZONE = -155
+SQL_VARIANT = -150
 
 FieldInfo = namedtuple("FieldInfo", BaseFieldInfo._fields + ("comment",))
 TableInfo = namedtuple("TableInfo", BaseTableInfo._fields + ("comment",))

testapp/tests/test_fields.py

@@ -4,6 +4,7 @@
 from django.test import TestCase
 
 from ..models import UUIDModel, Customer_name, Customer_address
+from django.db import connections
 
 
 class TestUUIDField(TestCase):
@@ -34,3 +35,15 @@ def test_random_order_by(self):
             names.append(list(Customer_name.objects.order_by('?')))
 
         self.assertNotEqual(names.count(names[0]), 20)
+
+
+class TestSQLVarient(TestCase):
+    def test_sql_varient(self):
+        connection = connections['default']
+        with connection.cursor() as cursor:
+            cursor.execute("CREATE TABLE sqlVarientTest(targetCol sql_variant, colB INT)")
+            cursor.execute("INSERT INTO sqlVarientTest values (CAST(46279.1 as decimal(8,2)), 1689)")
+            cursor.execute("SELECT targetCol FROM sqlVarientTest")
+
+            rows = cursor.fetchall()
+            self.assertEqual(len(rows), 1)