A 5.5 version of the fix for Bug #54360 "Deadlock DROP/ALTER/CREATE

DATABASE with open HANDLER"

Remove LOCK_create_db, database name locks, and use metadata locks instead.
This exposes CREATE/DROP/ALTER DATABASE statements to the graph-based
deadlock detector in MDL, and paves the way for a safe, deadlock-free
implementation of RENAME DATABASE.

Database DDL statements will now take exclusive metadata locks on
the database name, while table/view/routine DDL statements take
intention exclusive locks on the database name. This prevents race
conditions between database DDL and table/view/routine DDL.
(e.g. DROP DATABASE with concurrent CREATE/ALTER/DROP TABLE)

By adding database name locks, this patch implements
WL#4450 "DDL locking: CREATE/DROP DATABASE must use database locks" and
WL#4985 "DDL locking: namespace/hierarchical locks".

The patch also changes code to use init_one_table() where appropriate.
The new lock_table_names() function requires TABLE_LIST::db_length to
be set correctly, and this is taken care of by init_one_table().

This patch also adds a simple template to help work with 
the mysys HASH data structure.

Most of the patch was written by Konstantin Osipov.

1 files changed, 1 insertions, 2 deletions

diff --git a/sql/lock.h b/sql/lock.h
index 4bdf0085d07..0083dd3ba18 100644
--- a/sql/lock.h
+++ b/sql/lock.h
@@ -62,8 +62,7 @@ bool mysql_lock_abort_for_thread(THD *thd, TABLE *table);
 MYSQL_LOCK *mysql_lock_merge(MYSQL_LOCK *a,MYSQL_LOCK *b);
 void broadcast_refresh(void);
 /* Lock based on name */
-bool lock_table_names(THD *thd, TABLE_LIST *table_list);
-void unlock_table_names(THD *thd);
+bool lock_schema_name(THD *thd, const char *db);
 /* Lock based on stored routine name */
 bool lock_routine_name(THD *thd, bool is_function, const char *db,
                        const char *name);