django: add DatabaseIntrospection.get_table_description() stub

refs #248

Author: timgraham

packages/django-google-spanner/spanner/django/introspection.py

@@ -5,12 +5,44 @@
 # https://developers.google.com/open-source/licenses/bsd
 
 from django.db.backends.base.introspection import (
-    BaseDatabaseIntrospection, TableInfo,
+    BaseDatabaseIntrospection, FieldInfo, TableInfo,
 )
+from google.cloud.spanner_v1.proto import type_pb2
 
 
 class DatabaseIntrospection(BaseDatabaseIntrospection):
+    data_types_reverse = {
+        type_pb2.BOOL: 'BooleanField',
+        type_pb2.BYTES: 'BinaryField',
+        type_pb2.DATE: 'DateField',
+        type_pb2.FLOAT64: 'FloatField',
+        type_pb2.INT64: 'IntegerField',
+        type_pb2.STRING: 'TextField',
+        type_pb2.TIMESTAMP: 'DateTimeField',
+    }
+
     def get_table_list(self, cursor):
         """Return a list of table and view names in the current database."""
         # The second TableInfo field is 't' for table or 'v' for view.
         return [TableInfo(row[0], 't') for row in cursor.list_tables()]
+
+    def get_table_description(self, cursor, table_name):
+        """
+        Return a description of the table with the DB-API cursor.description
+        interface.
+        """
+        cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
+        return [
+            FieldInfo(
+                line.name,
+                line.type_code,
+                # TODO: Fill these in as they're implemented.
+                None,  # display_size
+                None,  # internal_size
+                None,  # precision
+                None,  # scale
+                None,  # null_ok
+                None,  # default
+            )
+            for line in cursor.description
+        ]