MDL_lock_guard Class Reference

Utility class to allow RAII pattern with MDL_request and MDL_context classes. More...

#include <rpl_rli.h>

Public Member Functions
	MDL_lock_guard (THD *target)
	Constructor that initializes the object and the target THD object but doesn't try to acquire any lock. More...
	MDL_lock_guard (THD *target, MDL_key::enum_mdl_namespace namespace_arg, enum_mdl_type mdl_type_arg, bool blocking=false)
	Constructor that initializes the object and the target THD object and tries to acquire the lock identified by namespace_arg with MDL type identified by mdl_type_arg. More...
virtual	~MDL_lock_guard ()
	Destructor that unlocks all acquired locks. More...
bool	lock (MDL_key::enum_mdl_namespace namespace_arg, enum_mdl_type mdl_type_arg, bool blocking=false)
	Uses the target THD object MDL context to acquire the lock identified by namespace_arg with MDL type identified by mdl_type_arg. More...
bool	is_locked ()
	Returns whether or not the lock as been acquired within this object life-cycle. More...

Private Attributes
THD *	m_target
	The THD object holding the MDL context used for acquiring/releasing. More...
MDL_request	m_request
	The MDL request holding the MDL ticket issued upon acquisition. More...

Detailed Description

Utility class to allow RAII pattern with MDL_request and MDL_context classes.

Constructor & Destructor Documentation

MDL_lock_guard() [1/2]

MDL_lock_guard::MDL_lock_guard

(

THD *

target

)

Constructor that initializes the object and the target THD object but doesn't try to acquire any lock.

Parameters

target

THD object, source for the MDL_context to use.

MDL_lock_guard() [2/2]

MDL_lock_guard::MDL_lock_guard	(	THD *	target,
		MDL_key::enum_mdl_namespace	namespace_arg,
		enum_mdl_type	mdl_type_arg,
		bool	blocking = false
	)

Constructor that initializes the object and the target THD object and tries to acquire the lock identified by namespace_arg with MDL type identified by mdl_type_arg.

If the blocking parameter is true, it will instantly try to acquire the lock and block. If the blocking parameter is false, it will first test if the lock is already acquired and only try to lock if no conflicting lock is already acquired.

Parameters

target	THD object, source for the MDL_context to use.
namespace_arg	MDL key namespace to acquire the lock from.
mdl_type_arg	MDL acquisition type
blocking	whether or not the execution should block if the lock is already acquired.

~MDL_lock_guard()

MDL_lock_guard::~MDL_lock_guard ( )

virtual

Destructor that unlocks all acquired locks.

Member Function Documentation

is_locked()

bool MDL_lock_guard::is_locked

(

)

Returns whether or not the lock as been acquired within this object life-cycle.

Returns

true if the lock has been acquired within this object life-cycle.

lock()

bool MDL_lock_guard::lock	(	MDL_key::enum_mdl_namespace	namespace_arg,
		enum_mdl_type	mdl_type_arg,
		bool	blocking = false
	)

Uses the target THD object MDL context to acquire the lock identified by namespace_arg with MDL type identified by mdl_type_arg.

If the blocking parameter is true, it will instantly try to acquire the lock and block. If the blocking parameter is false, it will first test if the lock is already acquired and only try to lock if no conflicting lock is already acquired.

The lock is determined to have been acquired if the THD object MDL context hasn't already a lock and the lock is acquired. In other words, if the MDL context already has acquired the lock, the method will return failure.

Parameters

namespace_arg	MDL key namespace to acquire the lock from.
mdl_type_arg	MDL acquisition type
blocking	whether or not the execution should block if the lock is already acquired.

Returns

false if the lock has been acquired by this method invocation and true if not.

Member Data Documentation

m_request

MDL_request MDL_lock_guard::m_request

private

The MDL request holding the MDL ticket issued upon acquisition.

m_target

THD* MDL_lock_guard::m_target

private

The THD object holding the MDL context used for acquiring/releasing.

---

The documentation for this class was generated from the following files:

• sql/rpl_rli.h
• sql/rpl_rli.cc