MDL_context_backup_manager Class Reference

Class which is used to store MDL locks associated with XA transactions in prepared state which clients have disconnected. More...

#include <mdl_context_backup.h>

Classes
class	MDL_context_backup
	Wrapper around MDL_context class which allows to store it in backup manager's collection. More...

Public Member Functions
	MDL_context_backup_manager (const MDL_context_backup_manager &)=delete
void	operator= (const MDL_context_backup_manager &)=delete
bool	create_backup (const MDL_context *context, const uchar *key, const size_t keylen)
	Create backup from given MDL_context by cloning all transactional locks to backup context and adds to backup context manager collection. More...
bool	create_backup (MDL_request_list *mdl_requests, const uchar *key, const size_t keylen)
	Create backup MDL_context, process request on it and add to backup context manager collection. More...
bool	restore_backup (MDL_context *mdl_context, const uchar *key, const size_t keylen)
	Restore locks from backup to given MDL_context. More...
void	delete_backup (const uchar *key, const size_t keylen)
	Delete backup context and release associated locks. More...

Static Public Member Functions
static bool	init ()
	Initialize member variables and singleton object. More...
static MDL_context_backup_manager &	instance ()
	Return singleton object. More...
static void	destroy ()
	Cleanup and delete singleton object. More...

Private Types
typedef std::basic_string< uchar >	MDL_context_backup_key
	Key for uniquely identifying MDL_context in the MDL_context_backup map. More...
typedef std::map< MDL_context_backup_key, std::unique_ptr< MDL_context_backup >, std::less< MDL_context_backup_key >, Malloc_allocator< std::pair< const MDL_context_backup_key, std::unique_ptr< MDL_context_backup > > > >	Element_map_type

Private Member Functions
	MDL_context_backup_manager (PSI_memory_key key)
	~MDL_context_backup_manager ()
	destroy mutex and clear backup map More...
bool	check_key_exist (const MDL_context_backup_key &key_obj)
	Check for presence of a record with specified key. More...

Static Private Member Functions
static void	init_psi_keys (void)

Private Attributes
Element_map_type	m_backup_map
mysql_mutex_t	m_LOCK_mdl_context_backup

Static Private Attributes
static MDL_context_backup_manager *	m_single = nullptr

Detailed Description

Class which is used to store MDL locks associated with XA transactions in prepared state which clients have disconnected.

These locks are not associated with any particular THD/thread. Later they will be retrieved by the thread which attempts to process the prepared XA transaction.

This is singleton class. It contains map where each element represents MDL_context of disconnected prepared XA transaction and holds related metadata locks.

Member Typedef Documentation

Element_map_type

typedef std::map< MDL_context_backup_key, std::unique_ptr<MDL_context_backup>, std::less<MDL_context_backup_key>, Malloc_allocator<std::pair<const MDL_context_backup_key, std::unique_ptr<MDL_context_backup> > > > MDL_context_backup_manager::Element_map_type

private

MDL_context_backup_key

typedef std::basic_string<uchar> MDL_context_backup_manager::MDL_context_backup_key

private

Key for uniquely identifying MDL_context in the MDL_context_backup map.

Constructor & Destructor Documentation

MDL_context_backup_manager() [1/2]

MDL_context_backup_manager::MDL_context_backup_manager ( PSI_memory_key  key )

private

MDL_context_backup_manager() [2/2]

MDL_context_backup_manager::MDL_context_backup_manager ( const MDL_context_backup_manager &  )

delete

~MDL_context_backup_manager()

MDL_context_backup_manager::~MDL_context_backup_manager ( )

private

destroy mutex and clear backup map

Member Function Documentation

check_key_exist()

bool MDL_context_backup_manager::check_key_exist ( const MDL_context_backup_key &  key_obj )

private

Check for presence of a record with specified key.

Parameters

[in]

key_obj

Key to identity MDL_context

Returns

true if there is a record for specified key, else false

create_backup() [1/2]

bool MDL_context_backup_manager::create_backup	(	const MDL_context *	context,
		const uchar *	key,
		const size_t	keylen
	)

Create backup from given MDL_context by cloning all transactional locks to backup context and adds to backup context manager collection.

This method is used during user's session disconnect for storing MDL locks acquired by prepared XA transaction(s).

This function does not set error codes beyond what is set by the functions it calls.

Parameters

[in]	context	MDL_context from which backup is created.
[in]	key	Key to identity MDL_context
[in]	keylen	Key Length

Return values

true	Error, e.g. Fail to create backup object, fail to clone locks.
false	Success or a backup already exist for this key.

create_backup() [2/2]

bool MDL_context_backup_manager::create_backup	(	MDL_request_list *	mdl_requests,
		const uchar *	key,
		const size_t	keylen
	)

Create backup MDL_context, process request on it and add to backup context manager collection.

This method is called during server start up in order to acquire MDL locks held by prepared XA transactions existed before server shutdown.

This function does not set error codes beyond what is set by the functions it calls.

Parameters

[in]	mdl_requests	Requests need to be processed and backed up.
[in]	key	Key to identity MDL_context
[in]	keylen	Key Length

Return values

true	Error, e.g. Fail to create backup object, fail to clone locks.
false	Success or a backup already exist for this key.

delete_backup()

void MDL_context_backup_manager::delete_backup	(	const uchar *	key,
		const size_t	keylen
	)

Delete backup context and release associated locks.

Parameters

[in]	key	Key to identity MDL_context
[in]	keylen	Key Length

destroy()

void MDL_context_backup_manager::destroy ( )

static

Cleanup and delete singleton object.

init()

bool MDL_context_backup_manager::init ( )

static

Initialize member variables and singleton object.

init_psi_keys()

void MDL_context_backup_manager::init_psi_keys ( void  )

staticprivate

instance()

MDL_context_backup_manager & MDL_context_backup_manager::instance ( )

static

Return singleton object.

operator=()

void MDL_context_backup_manager::operator= ( const MDL_context_backup_manager &  )

delete

restore_backup()

bool MDL_context_backup_manager::restore_backup	(	MDL_context *	mdl_context,
		const uchar *	key,
		const size_t	keylen
	)

Restore locks from backup to given MDL_context.

This function does not set error codes beyond what is set by the functions it calls.

Parameters

[out]	mdl_context	MDL_context to which backup is restored.
[in]	key	Key to identity MDL_context
[in]	keylen	Key Length

Return values

true	Error, e.g. There is no element in the collection matching given key, fail to restore locks.
false	Success

Member Data Documentation

m_backup_map

Element_map_type MDL_context_backup_manager::m_backup_map

private

m_LOCK_mdl_context_backup

mysql_mutex_t MDL_context_backup_manager::m_LOCK_mdl_context_backup

private

m_single

MDL_context_backup_manager * MDL_context_backup_manager::m_single = nullptr

staticprivate

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

• sql/mdl_context_backup.h
• sql/mdl_context_backup.cc