MDEV-5619: CREATE OR REPLACE does not release MDL_EXCLUSIVE upon failure

mysql-test/r/create_or_replace.result:
  Added test of releasing of metadata locks
mysql-test/t/create_or_replace.test:
  Added test of releasing of metadata locks
sql/handler.h:
  Added marker if table was deleted as part of CREATE OR REPLACE
sql/sql_base.cc:
  Added Locked_tables_list::unlock_locked_table()
sql/sql_class.h:
  New prototypes
sql/sql_insert.cc:
  Unlock metadata locks for deleted table in case of error. Also do unlock tables if this was the only locked table.
sql/sql_table.cc:
  Unlock metadata locks for deleted table in case of error. Also do unlock tables if this was the only locked table.

1 files changed, 32 insertions, 0 deletions

diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 82f98e0604b..bb15562b8f8 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -2722,6 +2722,38 @@ Locked_tables_list::unlock_locked_tables(THD *thd)
   reset();
 }
 
+
+/**
+  Remove all meta data locks associated with table and release locked
+  table mode if there is no locked tables anymore
+*/
+
+void
+Locked_tables_list::unlock_locked_table(THD *thd, MDL_ticket *mdl_ticket)
+{
+  /*
+    Ensure we are in locked table mode.
+    As this function is only called on error condition it's better
+    to check this condition here than in the caller.
+  */
+  if (thd->locked_tables_mode != LTM_LOCK_TABLES)
+    return;
+
+  if (mdl_ticket)
+  {
+    /*
+      Under LOCK TABLES we may have several instances of table open
+      and locked and therefore have to remove several metadata lock
+      requests associated with them.
+    */
+    thd->mdl_context.release_all_locks_for_name(mdl_ticket);
+  }
+
+  if (thd->lock->table_count == 0)
+    unlock_locked_tables(thd);
+}
+
+
 /*
   Free memory allocated for storing locks
 */