MDL_key Class Reference

#include <mdl.h>

List of all members.

Public Types
enum	enum_mdl_namespace {   GLOBAL = 0, SCHEMA, TABLE, FUNCTION,   PROCEDURE, TRIGGER, EVENT, COMMIT,   NAMESPACE_END }
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
enum_mdl_namespace	mdl_namespace () const
void	mdl_key_init (enum_mdl_namespace mdl_namespace, const char *db, const char *name)
void	mdl_key_init (const MDL_key *rhs)
bool	is_equal (const MDL_key *rhs) const
int	cmp (const MDL_key *rhs) const
	MDL_key (const MDL_key *rhs)
	MDL_key (enum_mdl_namespace namespace_arg, const char *db_arg, const char *name_arg)
const PSI_stage_info *	get_wait_state_name () const

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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>+

Elsewhere in the comments this triple will be referred to simply as "key" or "name".

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Member Enumeration Documentation

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

• 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 Note that although there isn't metadata locking on triggers, it's necessary to have a separate namespace for them since MDL_key is also used outside of the MDL subsystem.

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Member Function Documentation

int MDL_key::cmp

(

const MDL_key *

rhs

)

const [inline]

Compare two MDL keys lexicographically.

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.

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>="">+ mdl_namespace Id of namespace of object to be locked

Parameters:

db	Name of database to which the object belongs
name	Name of of the object
key	Where to store the the MDL key.

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

• mdl.h
• mdl.cc