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

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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.
This commit is contained in:
Jon Olav Hauglid
2010-07-01 15:53:46 +02:00
parent 34e409fafa
commit 41a3dfe490
28 changed files with 1300 additions and 652 deletions
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10
sql/sql_base.h
View File

@ -205,6 +205,9 @@ int setup_ftfuncs(SELECT_LEX* select);
int init_ftfuncs(THD *thd, SELECT_LEX* select, bool no_order);
void wait_for_condition(THD *thd, mysql_mutex_t *mutex,
mysql_cond_t *cond);
bool lock_table_names(THD *thd, TABLE_LIST *table_list,
TABLE_LIST *table_list_end, ulong lock_wait_timeout,
uint flags);
bool open_tables(THD *thd, TABLE_LIST **tables, uint *counter, uint flags,
Prelocking_strategy *prelocking_strategy);
/* open_and_lock_tables with optional derived handling */
@ -480,8 +483,6 @@ public:
return m_start_of_statement_svp;
}
MDL_request *get_global_mdl_request(THD *thd);
inline ulong get_timeout() const
{
return m_timeout;
@ -498,11 +499,6 @@ private:
*/
TABLE_LIST *m_failed_table;
MDL_ticket *m_start_of_statement_svp;
/**
Request object for global intention exclusive lock which is acquired during
opening tables for statements which take upgradable shared metadata locks.
*/
MDL_request *m_global_mdl_request;
/**
Lock timeout in seconds. Initialized to LONG_TIMEOUT when opening system
tables or to the "lock_wait_timeout" system variable for regular tables.