Updated/added copyright headers

1 files changed, 19 insertions, 6 deletions

diff --git a/sql/mdl.h b/sql/mdl.h
index 04298413605..fb2de45b831 100644
--- a/sql/mdl.h
+++ b/sql/mdl.h
@@ -1,6 +1,6 @@
 #ifndef MDL_H
 #define MDL_H
-/* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -152,11 +152,24 @@ enum enum_mdl_type {
 
 /** Duration of metadata lock. */
 
-enum enum_mdl_duration { MDL_STATEMENT= 0,
-                         MDL_TRANSACTION,
-                         MDL_EXPLICIT,
-                         /* This should be the last ! */
-                         MDL_DURATION_END };
+enum enum_mdl_duration {
+  /**
+    Locks with statement duration are automatically released at the end
+    of statement or transaction.
+  */
+  MDL_STATEMENT= 0,
+  /**
+    Locks with transaction duration are automatically released at the end
+    of transaction.
+  */
+  MDL_TRANSACTION,
+  /**
+    Locks with explicit duration survive the end of statement and transaction.
+    They have to be released explicitly by calling MDL_context::release_lock().
+  */
+  MDL_EXPLICIT,
+  /* This should be the last ! */
+  MDL_DURATION_END };
 
 
 /** Maximal length of key for metadata locking subsystem. */