MDL_key Struct Reference

Metadata lock object key. More...

#include <mdl.h>

Public Types
enum	enum_mdl_namespace {   GLOBAL = 0 , BACKUP_LOCK , TABLESPACE , SCHEMA ,   TABLE , FUNCTION , PROCEDURE , TRIGGER ,   EVENT , COMMIT , USER_LEVEL_LOCK , LOCKING_SERVICE ,   SRID , ACL_CACHE , COLUMN_STATISTICS , RESOURCE_GROUPS ,   FOREIGN_KEY , CHECK_CONSTRAINT , NAMESPACE_END }
	Object namespaces. More...

Public Member Functions
const uchar *	ptr () const
uint	length () const
const char *	db_name () const
uint	db_name_length () const
const char *	name () const
uint	name_length () const
const char *	col_name () const
uint	col_name_length () const
enum_mdl_namespace	mdl_namespace () const
void	mdl_key_init (enum_mdl_namespace mdl_namespace, const char *db, const char *name)
	Construct a metadata lock key from a triplet (mdl_namespace, database and name). More...
void	mdl_key_init (enum_mdl_namespace mdl_namespace, const char *db, const char *name, const char *column_name)
	Construct a metadata lock key from a quadruplet (mdl_namespace, database, table and column name). More...
void	mdl_key_init (enum_mdl_namespace mdl_namespace, const char *db, const char *normalized_name, size_t normalized_name_len, const char *name)
	Construct a metadata lock key from a quadruplet (mdl_namespace, database, normalized object name buffer and the object name). More...
void	mdl_key_init (enum_mdl_namespace mdl_namespace, const char *part_key, size_t part_key_length, size_t db_length)
	Construct a metadata lock key from namespace and partial key, which contains info about object database and name. More...
void	mdl_key_init (const MDL_key *rhs)
void	reset ()
bool	is_equal (const MDL_key *rhs) const
int	cmp (const MDL_key *rhs) const
	Compare two MDL keys lexicographically. More...
	MDL_key (const MDL_key &rhs)
MDL_key &	operator= (const MDL_key &rhs)
	MDL_key (enum_mdl_namespace namespace_arg, const char *db_arg, const char *name_arg)
	MDL_key ()=default
const PSI_stage_info *	get_wait_state_name () const
	Get thread state name to be used in case when we have to wait on resource identified by key. More...

Static Public Member Functions
static void	init_psi_keys ()

Private Member Functions
bool	use_normalized_object_name () const
	Check if normalized object name should be used. More...

Private Attributes
uint16	m_length {0}
uint16	m_db_name_length {0}
uint16	m_object_name_length {0}
char	m_ptr [MAX_MDLKEY_LENGTH] {0}

Static Private Attributes
static PSI_stage_info	m_namespace_to_wait_state_name [NAMESPACE_END]
	Thread state names to be used in case when we have to wait on resource belonging to certain namespace. More...

Detailed Description

Metadata lock object key.

A lock is requested or granted based on a fully qualified name and type. E.g. They key for a table consists of <0 (=table)>+<database>+<table name>. Elsewhere in the comments this triple will be referred to simply as "key" or "name".

Member Enumeration Documentation

enum_mdl_namespace

enum MDL_key::enum_mdl_namespace

Object namespaces.

Sic: when adding a new member to this enum make sure to update m_namespace_to_wait_state_name array in mdl.cc!

Different types of objects exist in different namespaces

• GLOBAL is used for the global read lock.
• BACKUP_LOCK is to block any operations that could cause inconsistent backup. Such operations are most DDL statements, and some administrative statements.
• TABLESPACE is for tablespaces.
• SCHEMA is for schemas (aka databases).
• TABLE is for tables and views.
• FUNCTION is for stored functions.
• PROCEDURE is for stored procedures.
• TRIGGER is for triggers.
• EVENT is for event scheduler events.
• COMMIT is for enabling the global read lock to block commits.
• USER_LEVEL_LOCK is for user-level locks.
• LOCKING_SERVICE is for the name plugin RW-lock service
• SRID is for spatial reference systems
• ACL_CACHE is for ACL caches
• COLUMN_STATISTICS is for column statistics, such as histograms
• RESOURCE_GROUPS is for resource groups.
• FOREIGN_KEY is for foreign key names.
• CHECK_CONSTRAINT is for check constraint names. Note that requests waiting for user-level locks get special treatment - waiting is aborted if connection to client is lost.

Enumerator
GLOBAL
BACKUP_LOCK
TABLESPACE
SCHEMA
TABLE
FUNCTION
PROCEDURE
TRIGGER
EVENT
COMMIT
USER_LEVEL_LOCK
LOCKING_SERVICE
SRID
ACL_CACHE
COLUMN_STATISTICS
RESOURCE_GROUPS
FOREIGN_KEY
CHECK_CONSTRAINT
NAMESPACE_END

Constructor & Destructor Documentation

MDL_key() [1/3]

MDL_key::MDL_key ( const MDL_key &  rhs )

inline

MDL_key() [2/3]

MDL_key::MDL_key ( enum_mdl_namespace  namespace_arg, const char *  db_arg, const char *  name_arg  )

inline

MDL_key() [3/3]

MDL_key::MDL_key ( )

default

Member Function Documentation

cmp()

int MDL_key::cmp ( const MDL_key *  rhs ) const

inline

Compare two MDL keys lexicographically.

col_name()

const char * MDL_key::col_name ( ) const

inline

col_name_length()

uint MDL_key::col_name_length ( ) const

inline

db_name()

const char * MDL_key::db_name ( ) const

inline

db_name_length()

uint MDL_key::db_name_length ( ) const

inline

get_wait_state_name()

const PSI_stage_info * MDL_key::get_wait_state_name ( ) const

inline

Get thread state name to be used in case when we have to wait on resource identified by key.

init_psi_keys()

void MDL_key::init_psi_keys ( )

static

is_equal()

bool MDL_key::is_equal ( const MDL_key *  rhs ) const

inline

length()

uint MDL_key::length ( ) const

inline

mdl_key_init() [1/5]

void MDL_key::mdl_key_init ( const MDL_key *  rhs )

inline

mdl_key_init() [2/5]

void MDL_key::mdl_key_init ( enum_mdl_namespace  mdl_namespace, const char *  db, const char *  name  )

inline

Construct a metadata lock key from a triplet (mdl_namespace, database and name).

Remarks

The key for a table is <mdl_namespace>+<database name>+<table name>

Parameters

mdl_namespace	Id of namespace of object to be locked
db	Name of database to which the object belongs
name	Name of of the object

mdl_key_init() [3/5]

void MDL_key::mdl_key_init ( enum_mdl_namespace  mdl_namespace, const char *  db, const char *  name, const char *  column_name  )

inline

Construct a metadata lock key from a quadruplet (mdl_namespace, database, table and column name).

Remarks

The key for a column is <mdl_namespace>+<database name>+<table name>+<column name>

Parameters

mdl_namespace	Id of namespace of object to be locked
db	Name of database to which the object belongs
name	Name of of the object
column_name	Name of of the column

mdl_key_init() [4/5]

void MDL_key::mdl_key_init ( enum_mdl_namespace  mdl_namespace, const char *  db, const char *  normalized_name, size_t  normalized_name_len, const char *  name  )

inline

Construct a metadata lock key from a quadruplet (mdl_namespace, database, normalized object name buffer and the object name).

Remarks

The key for a routine/event/resource group/trigger is <mdl_namespace>+<database name>+<normalized object name> additionally <object name> is stored in the same buffer for information purpose if buffer has sufficient space.

Routine, Event and Resource group names are case sensitive and accent sensitive. So normalized object name is used to form a MDL_key.

With the UTF8MB3 charset space reserved for the db name/object name is 64 * 3 bytes. utf8mb3_general_ci collation is used for the Routine, Event and Resource group names. With this collation, the normalized object name uses just 2 bytes for each character (max length = 64 * 2 bytes). MDL_key has still some space to store the object names. If there is a sufficient space for the object name in the MDL_key then it is stored in the MDL_key (similar to the column names in the MDL_key). Actual object name is used by the PFS. Not listing actual object name from the PFS should be OK when there is no space to store it (instead of increasing the MDL_key size). Object name is not used in the key comparisons. So only (mdl_namespace + strlen(db) + 1 + normalized_name_len + 1) value is stored in the m_length member.

Parameters

mdl_namespace	Id of namespace of object to be locked.
db	Name of database to which the object belongs.
normalized_name	Normalized name of the object.
normalized_name_len	Length of the normalized object name.
name	Name of the object.

mdl_key_init() [5/5]

void MDL_key::mdl_key_init ( enum_mdl_namespace  mdl_namespace, const char *  part_key, size_t  part_key_length, size_t  db_length  )

inline

Construct a metadata lock key from namespace and partial key, which contains info about object database and name.

Remarks

The partial key must be "<database>\0<name>\0".

Parameters

mdl_namespace	Id of namespace of object to be locked
part_key	Partial key.
part_key_length	Partial key length
db_length	Database name length.

mdl_namespace()

enum_mdl_namespace MDL_key::mdl_namespace ( ) const

inline

name()

const char * MDL_key::name ( ) const

inline

name_length()

uint MDL_key::name_length ( ) const

inline

operator=()

MDL_key & MDL_key::operator= ( const MDL_key &  rhs )

inline

ptr()

const uchar * MDL_key::ptr ( ) const

inline

reset()

void MDL_key::reset ( void  )

inline

use_normalized_object_name()

bool MDL_key::use_normalized_object_name ( ) const

inlineprivate

Check if normalized object name should be used.

Returns

true if normlized object name should be used, false otherwise.

Member Data Documentation

m_db_name_length

uint16 MDL_key::m_db_name_length {0}

private

m_length

uint16 MDL_key::m_length {0}

private

m_namespace_to_wait_state_name

PSI_stage_info MDL_key::m_namespace_to_wait_state_name

staticprivate

Initial value:

= {
    {0, "Waiting for global read lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for backup lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for tablespace metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for schema metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for table metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for stored function metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for stored procedure metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for trigger metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for event metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for commit lock", 0, PSI_DOCUMENT_ME},
    {0, "User lock", 0, PSI_DOCUMENT_ME}, 
    {0, "Waiting for locking service lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for spatial reference system lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for acl cache lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for column statistics lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for resource groups metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for foreign key metadata lock", 0, PSI_DOCUMENT_ME},
    {0, "Waiting for check constraint metadata lock", 0, PSI_DOCUMENT_ME}}

Thread state names to be used in case when we have to wait on resource belonging to certain namespace.

m_object_name_length

uint16 MDL_key::m_object_name_length {0}

private

m_ptr

char MDL_key::m_ptr[MAX_MDLKEY_LENGTH] {0}

private

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

• sql/mdl.h
• sql/mdl.cc