#include <assert.h>
#include <string.h>
#include <sys/types.h>
#include <algorithm>
#include <new>
#include <unordered_map>
#include "my_alloc.h"
#include "my_compiler.h"
#include "strmake.h"
#include "my_inttypes.h"
#include "my_psi_config.h"
#include "my_sys.h"
#include "my_systime.h"
#include "mysql/components/services/bits/mysql_cond_bits.h"
#include "mysql/components/services/bits/mysql_mutex_bits.h"
#include "mysql/components/services/bits/mysql_rwlock_bits.h"
#include "mysql/components/services/bits/psi_mdl_bits.h"
#include "mysql/components/services/bits/psi_stage_bits.h"
#include "mysql/psi/mysql_rwlock.h"
#include "mysql_com.h"
#include "sql/sql_plist.h"
#include "template_utils.h"

Classes
class	MDL_context_owner
	An interface to separate the MDL module from the THD, and the rest of the server code. More...

struct	MDL_key
	Metadata lock object key. More...

class	MDL_request
	A pending metadata lock request. More...

class	MDL_wait_for_graph_visitor
	An abstract class for inspection of a connected subgraph of the wait-for graph. More...

class	MDL_wait_for_subgraph
	Abstract class representing an edge in the waiters graph to be traversed by deadlock detection algorithm. More...

class	MDL_ticket
	A granted metadata lock. More...

class	MDL_ticket_store
	Keep track of MDL_ticket for different durations. More...

struct	MDL_ticket_store::MDL_ticket_handle
	Utility struct for representing a ticket pointer and its duration. More...

struct	MDL_ticket_store::Duration

struct	MDL_ticket_store::Hash

struct	MDL_ticket_store::Key_equal

class	MDL_savepoint
	Savepoint for MDL context. More...

class	MDL_wait
	A reliable way to wait on an MDL lock. More...

class	MDL_release_locks_visitor
	Base class to find out if the lock represented by a given ticket should be released. More...

class	MDL_context_visitor
	Abstract visitor class for inspecting MDL_context. More...

class	MDL_context
	Context of the owner of metadata locks. More...

Namespaces
namespace	mdl_unittest

Macros
#define	ENTER_COND(C, M, S, O) enter_cond(C, M, S, O, __func__, __FILE__, __LINE__)
	Start a wait on a condition. More...

#define	EXIT_COND(S) exit_cond(S, __func__, __FILE__, __LINE__)
	End a wait on a condition. More...

#define	MAX_MDLKEY_LENGTH (1 + NAME_LEN + 1 + NAME_LEN + 1)
	Maximal length of key for metadata locking subsystem. More...

#define	MDL_REQUEST_INIT(R, P1, P2, P3, P4, P5) (*R).init_with_source(P1, P2, P3, P4, P5, __FILE__, __LINE__)

#define	MDL_REQUEST_INIT_BY_KEY(R, P1, P2, P3) (*R).init_by_key_with_source(P1, P2, P3, __FILE__, __LINE__)

#define	MDL_REQUEST_INIT_BY_PART_KEY(R, P1, P2, P3, P4, P5, P6) (*R).init_by_part_key_with_source(P1, P2, P3, P4, P5, P6, __FILE__, __LINE__)

Typedefs
typedef I_P_List< MDL_request, I_P_List_adapter< MDL_request, &MDL_request::next_in_list, &MDL_request::prev_in_list >, I_P_List_counter >	MDL_request_list

Enumerations
enum	enum_mdl_type { MDL_INTENTION_EXCLUSIVE = 0 , MDL_SHARED , MDL_SHARED_HIGH_PRIO , MDL_SHARED_READ , MDL_SHARED_WRITE , MDL_SHARED_WRITE_LOW_PRIO , MDL_SHARED_UPGRADABLE , MDL_SHARED_READ_ONLY , MDL_SHARED_NO_WRITE , MDL_SHARED_NO_READ_WRITE , MDL_EXCLUSIVE , MDL_TYPE_END , MDL_INTENTION_EXCLUSIVE = 0 , MDL_SHARED , MDL_SHARED_HIGH_PRIO , MDL_SHARED_READ , MDL_SHARED_WRITE , MDL_SHARED_WRITE_LOW_PRIO , MDL_SHARED_UPGRADABLE , MDL_SHARED_READ_ONLY , MDL_SHARED_NO_WRITE , MDL_SHARED_NO_READ_WRITE , MDL_EXCLUSIVE , MDL_TYPE_END }
	Type of metadata lock request. More...

enum	enum_mdl_duration { MDL_STATEMENT = 0 , MDL_TRANSACTION , MDL_EXPLICIT , MDL_DURATION_END }
	Duration of metadata lock. More...

Functions
bool	mdl_unittest::test_drive_fix_pins (MDL_context *)

void	mdl_init ()
	Initialize the metadata locking subsystem. More...

void	mdl_destroy ()
	Release resources of metadata locking subsystem. More...

int32	mdl_get_unused_locks_count ()
	Get number of unused MDL_lock objects in MDL_map cache. More...

Variables
mysql_mutex_t	LOCK_open
	LOCK_open protects the following variables/objects: More...

ulong	max_write_lock_count

int32	mdl_locks_unused_locks_low_water
	Threshold for number of unused MDL_lock objects. More...

const int32	MDL_LOCKS_UNUSED_LOCKS_LOW_WATER_DEFAULT = 1000
	Default value for threshold for number of unused MDL_lock objects after exceeding which we start considering freeing them. More...

const double	MDL_LOCKS_UNUSED_LOCKS_MIN_RATIO = 0.25
	Ratio of unused/total MDL_lock objects after exceeding which we start trying to free unused MDL_lock objects (assuming that mdl_locks_unused_locks_low_water threshold is passed as well). More...

Macro Definition Documentation

◆ ENTER_COND

#define ENTER_COND	(	C,
		M,
		S,
		O
	)	enter_cond(C, M, S, O, __func__, __FILE__, __LINE__)

Start a wait on a condition.

Parameters

C	the condition to wait on
M	the associated mutex
S	the new stage to enter
O	the previous stage

See also: EXIT_COND().

◆ EXIT_COND

#define EXIT_COND ( S ) exit_cond(S, __func__, __FILE__, __LINE__)

End a wait on a condition.

Parameters

S	the new stage to enter

◆ MAX_MDLKEY_LENGTH

#define MAX_MDLKEY_LENGTH (1 + NAME_LEN + 1 + NAME_LEN + 1)

Maximal length of key for metadata locking subsystem.

◆ MDL_REQUEST_INIT

#define MDL_REQUEST_INIT	(	R,
		P1,
		P2,
		P3,
		P4,
		P5
	)	(*R).init_with_source(P1, P2, P3, P4, P5, __FILE__, __LINE__)

◆ MDL_REQUEST_INIT_BY_KEY

#define MDL_REQUEST_INIT_BY_KEY	(	R,
		P1,
		P2,
		P3
	)	(*R).init_by_key_with_source(P1, P2, P3, __FILE__, __LINE__)

◆ MDL_REQUEST_INIT_BY_PART_KEY

#define MDL_REQUEST_INIT_BY_PART_KEY	(	R,
		P1,
		P2,
		P3,
		P4,
		P5,
		P6
	)	(*R).init_by_part_key_with_source(P1, P2, P3, P4, P5, P6, __FILE__, __LINE__)

Typedef Documentation

◆ MDL_request_list

typedef I_P_List<MDL_request, I_P_List_adapter<MDL_request, &MDL_request::next_in_list, &MDL_request::prev_in_list>, I_P_List_counter> MDL_request_list

Enumeration Type Documentation

◆ enum_mdl_duration

enum enum_mdl_duration

Duration of metadata lock.

Enumerator
MDL_STATEMENT	Locks with statement duration are automatically released at the end of statement or transaction.
MDL_TRANSACTION	Locks with transaction duration are automatically released at the end of transaction.
MDL_EXPLICIT	Locks with explicit duration survive the end of statement and transaction. They have to be released explicitly by calling MDL_context::release_lock().
MDL_DURATION_END

◆ enum_mdl_type

enum enum_mdl_type

Type of metadata lock request.

See also: Comments for MDL_object_lock::can_grant_lock() and MDL_scoped_lock::can_grant_lock() for details.

Enumerator
MDL_INTENTION_EXCLUSIVE
MDL_SHARED
MDL_SHARED_HIGH_PRIO
MDL_SHARED_READ
MDL_SHARED_WRITE
MDL_SHARED_WRITE_LOW_PRIO
MDL_SHARED_UPGRADABLE
MDL_SHARED_READ_ONLY
MDL_SHARED_NO_WRITE
MDL_SHARED_NO_READ_WRITE
MDL_EXCLUSIVE
MDL_TYPE_END
MDL_INTENTION_EXCLUSIVE
MDL_SHARED
MDL_SHARED_HIGH_PRIO
MDL_SHARED_READ
MDL_SHARED_WRITE
MDL_SHARED_WRITE_LOW_PRIO
MDL_SHARED_UPGRADABLE
MDL_SHARED_READ_ONLY
MDL_SHARED_NO_WRITE
MDL_SHARED_NO_READ_WRITE
MDL_EXCLUSIVE
MDL_TYPE_END

Function Documentation

◆ mdl_destroy()

void mdl_destroy ( )

Release resources of metadata locking subsystem.

Destroys the global mutex and the condition variable. Called at server shutdown.

◆ mdl_get_unused_locks_count()

int32 mdl_get_unused_locks_count ( )

Get number of unused MDL_lock objects in MDL_map cache.

Mostly needed for unit-testing.

◆ mdl_init()

void mdl_init ( )

Initialize the metadata locking subsystem.

This function is called at server startup.

In particular, initializes the new global mutex and the associated condition variable: LOCK_mdl and COND_mdl. These locking primitives are implementation details of the MDL subsystem and are private to it.

Variable Documentation

◆ max_write_lock_count

ulong max_write_lock_count

extern

◆ mdl_locks_unused_locks_low_water

int32 mdl_locks_unused_locks_low_water

extern

Threshold for number of unused MDL_lock objects.

We will start considering freeing some unused objects only after exceeding this value and if unused/total objects ratio is high enough.

Normally this threshold is constant. It is exposed outside of MDL subsystem as a variable only in order to simplify unit testing.

◆ MDL_LOCKS_UNUSED_LOCKS_LOW_WATER_DEFAULT

const int32 MDL_LOCKS_UNUSED_LOCKS_LOW_WATER_DEFAULT = 1000

Default value for threshold for number of unused MDL_lock objects after exceeding which we start considering freeing them.

Only unit tests use different threshold value.

◆ MDL_LOCKS_UNUSED_LOCKS_MIN_RATIO

const double MDL_LOCKS_UNUSED_LOCKS_MIN_RATIO = 0.25

Ratio of unused/total MDL_lock objects after exceeding which we start trying to free unused MDL_lock objects (assuming that mdl_locks_unused_locks_low_water threshold is passed as well).

Note that this value should be high enough for our algorithm using random dives into hash to work well.

Classes

Namespaces

Macros

Typedefs

Enumerations

Functions

Variables