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-rw-r--r--sql/mdl.h25
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. */