1 files changed, 20 insertions, 13 deletions

diff --git a/sql/mdl.h b/sql/mdl.h
index 15a1976876b..b76d70763e7 100644
--- a/sql/mdl.h
+++ b/sql/mdl.h
@@ -15,23 +15,12 @@
    along with this program; if not, write to the Free Software Foundation,
    51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA */
 
-#if defined(__IBMC__) || defined(__IBMCPP__)
-/* Further down, "next_in_lock" and "next_in_context" have the same type,
-   and in "sql_plist.h" this leads to an identical signature, which causes
-   problems in function overloading.
-*/
-#pragma namemangling(v5)
-#endif
-
-
 #include "sql_plist.h"
 #include <my_sys.h>
 #include <m_string.h>
 #include <mysql_com.h>
 #include <lf.h>
 
-#include <algorithm>
-
 class THD;
 
 class MDL_context;
@@ -205,6 +194,12 @@ enum enum_mdl_type {
   */
   MDL_SHARED_UPGRADABLE,
   /*
+    A shared metadata lock for cases when we need to read data from table
+    and block all concurrent modifications to it (for both data and metadata).
+    Used by LOCK TABLES READ statement.
+  */
+  MDL_SHARED_READ_ONLY,
+  /*
     An upgradable shared metadata lock which blocks all attempts to update
     table data, allowing reads.
     A connection holding this kind of lock can read table metadata and read
@@ -376,8 +371,7 @@ public:
       character set is utf-8, we can safely assume that no
       character starts with a zero byte.
     */
-    using std::min;
-    return memcmp(m_ptr, rhs->m_ptr, min(m_length, rhs->m_length));
+    return memcmp(m_ptr, rhs->m_ptr, MY_MIN(m_length, rhs->m_length));
   }
 
   MDL_key(const MDL_key *rhs)
@@ -486,6 +480,19 @@ public:
     from.ticket=  NULL; // that's what "move" means
   }
 
+  /**
+    Is this a request for a lock which allow data to be updated?
+
+    @note This method returns true for MDL_SHARED_UPGRADABLE type of
+          lock. Even though this type of lock doesn't allow updates
+          it will always be upgraded to one that does.
+  */
+  bool is_write_lock_request() const
+  {
+    return (type >= MDL_SHARED_WRITE &&
+            type != MDL_SHARED_READ_ONLY);
+  }
+
   /*
     This is to work around the ugliness of TABLE_LIST
     compiler-generated assignment operator. It is currently used