1 files changed, 15 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 1126fe7fce..1783b036a2 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -169,6 +169,14 @@ module ActiveRecord
         true
       end
 
+      # MySQL 4 technically support transaction isolation, but it is affected by a bug
+      # where the transaction level gets persisted for the whole session:
+      #
+      # http://bugs.mysql.com/bug.php?id=39170
+      def supports_transaction_isolation?
+        version[0] >= 5
+      end
+
       def native_database_types
         NATIVE_DATABASE_TYPES
       end
@@ -269,6 +277,13 @@ module ActiveRecord
         # Transactions aren't supported
       end
 
+      def begin_isolated_db_transaction(isolation)
+        execute "SET TRANSACTION ISOLATION LEVEL #{transaction_isolation_levels.fetch(isolation)}"
+        begin_db_transaction
+      rescue
+        # Transactions aren't supported
+      end
+
       def commit_db_transaction #:nodoc:
         execute "COMMIT"
       rescue