A granted metadata lock. More...

#include <mdl.h>

Inheritance diagram for MDL_ticket:

Public Types
enum	enum_psi_status { PENDING = 0 , GRANTED , PRE_ACQUIRE_NOTIFY , POST_RELEASE_NOTIFY }
	Status of lock request represented by the ticket as reflected in P_S. More...

Public Member Functions
bool	has_pending_conflicting_lock () const
	Check if we have any pending locks which conflict with existing shared lock. More...

MDL_context *	get_ctx () const

bool	is_upgradable_or_exclusive () const

enum_mdl_type	get_type () const

MDL_lock *	get_lock () const

const MDL_key *	get_key () const
	Return a key identifying this lock. More...

void	downgrade_lock (enum_mdl_type type)
	Downgrade an EXCLUSIVE or SHARED_NO_WRITE lock to shared metadata lock. More...

bool	has_stronger_or_equal_type (enum_mdl_type type) const
	Check if ticket represents metadata lock of "stronger" or equal type than specified one. More...

bool	is_incompatible_when_granted (enum_mdl_type type) const

bool	is_incompatible_when_waiting (enum_mdl_type type) const

bool	accept_visitor (MDL_wait_for_graph_visitor *dvisitor) override
	Implement MDL_wait_for_subgraph interface. More...

uint	get_deadlock_weight () const override
	Return the 'weight' of this ticket for the victim selection algorithm. More...

enum_mdl_duration	get_duration () const

void	set_duration (enum_mdl_duration dur)

Public Member Functions inherited from MDL_wait_for_subgraph
virtual	~MDL_wait_for_subgraph ()

Public Attributes
MDL_ticket *	next_in_context
	Pointers for participating in the list of lock requests for this context. More...

MDL_ticket **	prev_in_context

MDL_ticket *	next_in_lock
	Pointers for participating in the list of satisfied/pending requests for the lock. More...

MDL_ticket **	prev_in_lock

Private Member Functions
	MDL_ticket (MDL_context *ctx_arg, enum_mdl_type type_arg, enum_mdl_duration duration_arg)

	~MDL_ticket () override

	MDL_ticket (const MDL_ticket &)

MDL_ticket &	operator= (const MDL_ticket &)

Static Private Member Functions
static MDL_ticket *	create (MDL_context *ctx_arg, enum_mdl_type type_arg, enum_mdl_duration duration_arg)
	Auxiliary functions needed for creation/destruction of MDL_ticket objects. More...

static void	destroy (MDL_ticket *ticket)

Private Attributes
enum enum_mdl_type	m_type
	Type of metadata lock. More...

enum_mdl_duration	m_duration
	Duration of lock represented by this ticket. More...

MDL_context *	m_ctx
	Context of the owner of the metadata lock ticket. More...

MDL_lock *	m_lock
	Pointer to the lock object for this lock ticket. More...

bool	m_is_fast_path
	Indicates that ticket corresponds to lock acquired using "fast path" algorithm. More...

bool	m_hton_notified
	Indicates that ticket corresponds to lock request which required storage engine notification during its acquisition and requires storage engine notification after its release. More...

PSI_metadata_lock *	m_psi

Friends
class	MDL_context

Additional Inherited Members
Static Public Attributes inherited from MDL_wait_for_subgraph
static const uint	DEADLOCK_WEIGHT_CO = 0

static const uint	DEADLOCK_WEIGHT_DML = 25

static const uint	DEADLOCK_WEIGHT_ULL = 50

static const uint	DEADLOCK_WEIGHT_DDL = 100

Detailed Description

A granted metadata lock.

Warning: MDL_ticket members are private to the MDL subsystem.

Note

Multiple shared locks on a same object are represented by a single ticket. The same does not apply for other lock types.

There are two groups of MDL_ticket members:

"Externally accessible". These members can be accessed from threads/contexts different than ticket owner in cases when ticket participates in some list of granted or waiting tickets for a lock. Therefore one should change these members before including then to waiting/granted lists or while holding lock protecting those lists.
"Context private". Such members are private to thread/context owning this ticket. I.e. they should not be accessed from other threads/contexts.

Member Enumeration Documentation

◆ enum_psi_status

enum MDL_ticket::enum_psi_status

Status of lock request represented by the ticket as reflected in P_S.

Enumerator
PENDING
GRANTED
PRE_ACQUIRE_NOTIFY
POST_RELEASE_NOTIFY

Constructor & Destructor Documentation

◆ MDL_ticket() [1/2]

MDL_ticket::MDL_ticket	(	MDL_context *	ctx_arg,
		enum_mdl_type	type_arg,
		enum_mdl_duration	duration_arg
	)

inlineprivate

◆ ~MDL_ticket()

MDL_ticket::~MDL_ticket ( )

inlineoverrideprivate

◆ MDL_ticket() [2/2]

MDL_ticket::MDL_ticket ( const MDL_ticket & )

private

Member Function Documentation

◆ accept_visitor()

bool MDL_ticket::accept_visitor ( MDL_wait_for_graph_visitor * gvisitor )

overridevirtual

Implement MDL_wait_for_subgraph interface.

Traverse a portion of wait-for graph which is reachable through the edge represented by this ticket and search for deadlocks.

Return values

true	A deadlock is found. A pointer to deadlock victim is saved in the visitor.
false	TBD

Implements MDL_wait_for_subgraph.

◆ create()

MDL_ticket * MDL_ticket::create	(	MDL_context *	ctx_arg,
		enum_mdl_type	type_arg,
		enum_mdl_duration	duration_arg
	)

staticprivate

Auxiliary functions needed for creation/destruction of MDL_ticket objects.

◆ destroy()

void MDL_ticket::destroy ( MDL_ticket * ticket )

staticprivate

◆ downgrade_lock()

void MDL_ticket::downgrade_lock ( enum_mdl_type new_type )

Downgrade an EXCLUSIVE or SHARED_NO_WRITE lock to shared metadata lock.

Parameters

new_type Type of lock to which exclusive lock should be downgraded.

◆ get_ctx()

MDL_context * MDL_ticket::get_ctx ( ) const

inline

◆ get_deadlock_weight()

uint MDL_ticket::get_deadlock_weight ( ) const

overridevirtual

Return the 'weight' of this ticket for the victim selection algorithm.

Requests with lower weight are preferred to requests with higher weight when choosing a victim.

Note: When MDL_context::m_force_dml_deadlock_weight is set, the return value of this method is ignored and DEADLOCK_WEIGHT_DML is used for the context.

Implements MDL_wait_for_subgraph.

◆ get_duration()

enum_mdl_duration MDL_ticket::get_duration ( ) const

inline

◆ get_key()

const MDL_key * MDL_ticket::get_key ( ) const

Return a key identifying this lock.

◆ get_lock()

MDL_lock * MDL_ticket::get_lock ( ) const

inline

◆ get_type()

enum_mdl_type MDL_ticket::get_type ( ) const

inline

◆ has_pending_conflicting_lock()

bool MDL_ticket::has_pending_conflicting_lock ( ) const

Check if we have any pending locks which conflict with existing shared lock.

Precondition: The ticket must match an acquired lock.

Returns: true if there is a conflicting lock request, false otherwise.

◆ has_stronger_or_equal_type()

bool MDL_ticket::has_stronger_or_equal_type ( enum_mdl_type type ) const

Check if ticket represents metadata lock of "stronger" or equal type than specified one.

I.e. if metadata lock represented by ticket won't allow any of locks which are not allowed by specified type of lock.

Returns: true if ticket has stronger or equal type false otherwise.

◆ is_incompatible_when_granted()

bool MDL_ticket::is_incompatible_when_granted ( enum_mdl_type type ) const

◆ is_incompatible_when_waiting()

bool MDL_ticket::is_incompatible_when_waiting ( enum_mdl_type type ) const

◆ is_upgradable_or_exclusive()

bool MDL_ticket::is_upgradable_or_exclusive ( ) const

inline

◆ operator=()

MDL_ticket & MDL_ticket::operator= ( const MDL_ticket & )

private

◆ set_duration()

void MDL_ticket::set_duration ( enum_mdl_duration dur )

inline

Friends And Related Function Documentation

◆ MDL_context

friend class MDL_context

friend

Member Data Documentation

◆ m_ctx

MDL_context* MDL_ticket::m_ctx

private

Context of the owner of the metadata lock ticket.

Externally accessible.

◆ m_duration

enum_mdl_duration MDL_ticket::m_duration

private

Duration of lock represented by this ticket.

Context private. Debug-only.

◆ m_hton_notified

bool MDL_ticket::m_hton_notified

private

Indicates that ticket corresponds to lock request which required storage engine notification during its acquisition and requires storage engine notification after its release.

◆ m_is_fast_path

bool MDL_ticket::m_is_fast_path

private

Indicates that ticket corresponds to lock acquired using "fast path" algorithm.

Particularly this means that it was not included into MDL_lock::m_granted bitmap/list and instead is accounted for by MDL_lock::m_fast_path_locks_granted_counter

◆ m_lock

MDL_lock* MDL_ticket::m_lock

private

Pointer to the lock object for this lock ticket.

Externally accessible.

◆ m_psi

PSI_metadata_lock* MDL_ticket::m_psi

private

◆ m_type

enum enum_mdl_type MDL_ticket::m_type

private

Type of metadata lock.

Externally accessible.

◆ next_in_context

MDL_ticket* MDL_ticket::next_in_context

Pointers for participating in the list of lock requests for this context.

Context private.

◆ next_in_lock

MDL_ticket* MDL_ticket::next_in_lock

Pointers for participating in the list of satisfied/pending requests for the lock.

Externally accessible.

◆ prev_in_context

MDL_ticket** MDL_ticket::prev_in_context

◆ prev_in_lock

MDL_ticket** MDL_ticket::prev_in_lock

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

sql/mdl.h
sql/mdl.cc

Public Types

Public Member Functions

Public Attributes

Private Member Functions

Static Private Member Functions

Private Attributes

Friends

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ enum_psi_status

Constructor & Destructor Documentation

◆ MDL_ticket() [1/2]

◆ ~MDL_ticket()

◆ MDL_ticket() [2/2]

Member Function Documentation

◆ accept_visitor()

◆ create()

◆ destroy()

◆ downgrade_lock()

◆ get_ctx()

◆ get_deadlock_weight()

◆ get_duration()

◆ get_key()

◆ get_lock()

◆ get_type()

◆ has_pending_conflicting_lock()

◆ has_stronger_or_equal_type()

◆ is_incompatible_when_granted()

◆ is_incompatible_when_waiting()

◆ is_upgradable_or_exclusive()

◆ operator=()

◆ set_duration()

Friends And Related Function Documentation

◆ MDL_context

Member Data Documentation

◆ m_ctx

◆ m_duration

◆ m_hton_notified

◆ m_is_fast_path

◆ m_lock

◆ m_psi

◆ m_type

◆ next_in_context

◆ next_in_lock

◆ prev_in_context

◆ prev_in_lock