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#include "sql_priv.h"
#include "debug_sync.h"
#include "unireg.h"
#include "lock.h"
#include "sql_base.h"
#include "sql_parse.h"
#include "sql_acl.h"
#include <hash.h>
#include <assert.h>
#include "my_atomic.h"


#define GET_LOCK_UNLOCK   1


MYSQL_LOCKmysql_lock_tables (THD *thd, TABLE **tables, uint count, uint flags)
void mysql_unlock_tables (THD *thd, MYSQL_LOCK *sql_lock)
void mysql_unlock_some_tables (THD *thd, TABLE **table, uint count)
void mysql_unlock_read_tables (THD *thd, MYSQL_LOCK *sql_lock)
void mysql_lock_remove (THD *thd, MYSQL_LOCK *locked, TABLE *table)
void mysql_lock_abort (THD *thd, TABLE *table, bool upgrade_lock)
bool mysql_lock_abort_for_thread (THD *thd, TABLE *table)
MYSQL_LOCKmysql_lock_merge (MYSQL_LOCK *a, MYSQL_LOCK *b)
bool lock_schema_name (THD *thd, const char *db)
bool lock_object_name (THD *thd, MDL_key::enum_mdl_namespace mdl_type, const char *db, const char *name)


HASH open_cache

Detailed Description

Locking functions for mysql.

Because of the new concurrent inserts, we must first get external locks before getting internal locks. If we do it in the other order, the status information is not up to date when called from the lock handler.


When not using LOCK TABLES:

When using LOCK TABLES:

The tables used can only be tables used in LOCK TABLES or a temporary table.

If table_handler->external_lock(thd, locktype) fails, we call table_handler->external_lock(thd, F_UNLCK) for each table that was locked, excluding one that caused failure. That means handler must cleanup itself in case external_lock() fails.

Change to use my_malloc() ONLY when using LOCK TABLES command or when we are forced to use mysql_lock_merge.
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