Andrew Godwin avatar Andrew Godwin committed 00074f0 Merge

Merged in charettes/south/has-ddl-transaction-feature-detection (pull request #33)

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Files changed (2)


 from django.dispatch import dispatcher
 from django.conf import settings
 from django.utils.datastructures import SortedDict
+from django.utils.functional import cached_property
 from south.logger import get_logger
     Some of this code comes from Django Evolution.
-    # We assume the generic DB can handle DDL transactions. MySQL wil change this.
-    has_ddl_transactions = True
     alter_string_set_type = 'ALTER COLUMN %(column)s TYPE %(type)s'
     alter_string_set_null = 'ALTER COLUMN %(column)s DROP NOT NULL'
     alter_string_drop_null = 'ALTER COLUMN %(column)s SET NOT NULL'
-    has_check_constraints = True
     delete_check_sql = 'ALTER TABLE %(table)s DROP CONSTRAINT %(constraint)s'
-    allows_combined_alters = True
     add_column_string = 'ALTER TABLE %s ADD COLUMN %s;'
     delete_unique_sql = "ALTER TABLE %s DROP CONSTRAINT %s"
     delete_foreign_key_sql = 'ALTER TABLE %(table)s DROP CONSTRAINT %(constraint)s'
-    supports_foreign_keys = True
     max_index_name_length = 63
     drop_index_string = 'DROP INDEX %(index_name)s'
     delete_column_string = 'ALTER TABLE %s DROP COLUMN %s CASCADE;'
     rename_table_sql = "ALTER TABLE %s RENAME TO %s;"
     backend_name = None
     default_schema_name = "public"
+    # Features
+    allows_combined_alters = True
+    supports_foreign_keys = True
+    has_check_constraints = True
+    @cached_property
+    def has_ddl_transactions(self):
+        self._possibly_initialise()
+        connection = self._get_connection()
+        if connection.features.supports_transactions:
+            cursor = connection.cursor()
+            self.start_transaction()
+            cursor.execute('CREATE TABLE DDL_TRANSACTION_TEST (X INT)')
+            self.rollback_transaction()
+            try:
+                cursor.execute('CREATE TABLE DDL_TRANSACTION_TEST (X INT)')
+            except DatabaseError:
+                return False
+            else:
+                return True
+            finally:
+                cursor.execute('DROP TABLE DDL_TRANSACTION_TEST')
+        else:
+            return False
     def __init__(self, db_alias):
         self.debug = False


     drop_index_string = 'DROP INDEX %(index_name)s ON %(table_name)s'
     delete_primary_key_sql = "ALTER TABLE %(table)s DROP PRIMARY KEY"
     delete_foreign_key_sql = "ALTER TABLE %(table)s DROP FOREIGN KEY %(constraint)s"
-    allows_combined_alters = False
-    has_ddl_transactions = False
-    has_check_constraints = False
     delete_unique_sql = "ALTER TABLE %s DROP INDEX %s"
     rename_table_sql = "RENAME TABLE %s TO %s;"
+    allows_combined_alters = False
+    has_check_constraints = False
     geom_types = ['geometry', 'point', 'linestring', 'polygon']
     text_types = ['text', 'blob',]
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