This class abstracts some functionality used by XA statements involved in the second phase of the the XA two-phase commit, specifically, XA COMMIT and XA ROLLBACK SQL statements. More...

#include <sql_xa_second_phase.h>

Inheritance diagram for Sql_cmd_xa_second_phase:

[legend]

Public Member Functions
	Sql_cmd_xa_second_phase (xid_t *xid_arg)
	Class constructor. More...

virtual	~Sql_cmd_xa_second_phase () override=default

Public Member Functions inherited from Sql_cmd
virtual enum_sql_command	sql_command_code () const =0
	Return the command code for this statement. More...

bool	needs_explicit_preparation () const

bool	is_regular () const

bool	is_prepared () const

virtual bool	prepare (THD *)
	Prepare this SQL statement. More...

virtual bool	execute (THD *thd)=0
	Execute this SQL statement. More...

virtual bool	reprepare_on_execute_required () const
	Some SQL commands currently require re-preparation on re-execution of a prepared statement or stored procedure. More...

virtual void	cleanup (THD *)
	Command-specific reinitialization before execution of prepared statement. More...

void	set_owner (Prepared_statement *stmt)
	Set the owning prepared statement. More...

Prepared_statement *	owner () const
	Get the owning prepared statement. More...

void	set_as_part_of_sp ()
	Mark statement as part of procedure. More...

bool	is_part_of_sp () const

virtual bool	is_dml () const

virtual bool	is_single_table_plan () const

virtual bool	accept (THD , Select_lex_visitor )

virtual const MYSQL_LEX_CSTRING *	eligible_secondary_storage_engine () const
	Is this statement of a type and on a form that makes it eligible for execution in a secondary storage engine? More...

void	disable_secondary_storage_engine ()
	Disable use of secondary storage engines in this statement. More...

bool	secondary_storage_engine_disabled () const
	Has use of secondary storage engines been disabled for this statement? More...

void	use_secondary_storage_engine (const handlerton *hton)
	Mark the current statement as using a secondary storage engine. More...

bool	using_secondary_storage_engine () const
	Is this statement using a secondary storage engine? More...

const handlerton *	secondary_engine () const
	Get the handlerton of the secondary engine that is used for executing this statement, or nullptr if a secondary engine is not used. More...

void	set_optional_transform_prepared (bool value)

bool	is_optional_transform_prepared ()

Protected Member Functions
bool	find_and_initialize_xa_context (THD *thd)
	Tries to find and initialize the `Transaction_ctx` for the underlying detached XA transaction. More...

bool	acquire_locks (THD *thd)
	Tries to acquire the locks necessary to finalize the underlying detached XA transaction. More...

void	release_locks () const
	Release any locks acquires in `acquire_locks` still needing to be released. More...

void	setup_thd_context (THD *thd)
	Initializes the necessary parts of the `thd` parameter, transferring some of the detached XA transaction context to the active session. More...

bool	enter_commit_order (THD *thd)
	For replica applier threads, enters the wait on the commit order. More...

void	assign_xid_to_thd (THD *thd) const
	Sets the XID_STATE of the THD session object parameter as in detached state and copies into it the XID of the detached XA transaction. More...

void	exit_commit_order (THD *thd) const
	For replica applier threads, finishes the wait on the commit order and allows other threads to proceed. More...

void	cleanup_context (THD *thd) const
	Cleans up the THD context in order to prepare it for re-use. More...

void	dispose ()
	Disposes of member variables that need it, because destructors for `Sql_cmd` classes aren't invoked (since they are created in the internal memory pool, memory is disposed as a all block). More...

Protected Member Functions inherited from Sql_cmd
	Sql_cmd ()

virtual	~Sql_cmd ()

void	set_prepared ()
	Set this statement as prepared. More...

Protected Attributes
xid_t *	m_xid {nullptr}
	The XID associated with the underlying XA transaction. More...

MDL_savepoint	m_mdl_savepoint
	The MDL savepoint used to rollback the MDL context when transient errors occur. More...

std::shared_ptr< Transaction_ctx >	m_detached_trx_context {nullptr}
	The detached transaction context, retrieved from the transaction cache. More...

bool	m_gtid_error {false}
	Whether or not the initialization of GTIDs returned an error. More...

bool	m_need_clear_owned_gtid {false}
	Whether or not the OWNED_GTID related structures need to be cleaned. More...

bool	m_result {false}
	The incremental success of the several initialization and deinitialization steps. More...

Detailed Description

This class abstracts some functionality used by XA statements involved in the second phase of the the XA two-phase commit, specifically, XA COMMIT and XA ROLLBACK SQL statements.

Common usage of the available methods target the process of detached XA transactions, code pattern looks like:

bool Sql_cmd_xa_statement::process_detached_xa_statement(THD *thd) {
  DBUG_TRACE;

  if (this->find_and_initialize_xa_context(thd)) return true;
  if (this->acquire_locks(thd)) return true;
  raii::Sentry<> xa_lock_guard{
      [this]() -> void { this->release_locks(); }};
  this->setup_thd_context(thd);
  if (this->enter_commit_order(thd)) return true;

  this->assign_xid_to_thd(thd);

SPECIFIC STATEMENT EXECUTION HERE this->m_result = exec_statement(thd);

this->exit_commit_order(thd); this->cleanup_context(thd);

return this->m_result; }

See also: Sql_cmd

Constructor & Destructor Documentation

◆ Sql_cmd_xa_second_phase()

Sql_cmd_xa_second_phase::Sql_cmd_xa_second_phase ( xid_t * xid_arg )

Class constructor.

Parameters

xid_arg XID of the XA transacation about to be committed

◆ ~Sql_cmd_xa_second_phase()

virtual Sql_cmd_xa_second_phase::~Sql_cmd_xa_second_phase ( )

overridevirtualdefault

Member Function Documentation

◆ acquire_locks()

bool Sql_cmd_xa_second_phase::acquire_locks ( THD * thd )

protected

Tries to acquire the locks necessary to finalize the underlying detached XA transaction.

By function exit, all locks have been acquired or none.

Execution is as follows:

An MDL savepoint is set, in order to allow the rollback to this point if a timeout/locking error is triggered.
XID_STATE::m_xa_lock is acquired to prevent concurrent finalization of the transaction (triggered from different client connections, for instance).
Ensure that between steps 1. and 2. some other session didn't finalize the transaction, by confirming that the transaction is in the transaction cache and still in prepared state.
Acquire MDL commit locks.

Parameters

thd	The THD session object used to process the detached XA transaction.

Returns: false if all necessary locks were acquired, true otherwise.

◆ assign_xid_to_thd()

void Sql_cmd_xa_second_phase::assign_xid_to_thd ( THD * thd ) const

protected

Sets the XID_STATE of the THD session object parameter as in detached state and copies into it the XID of the detached XA transaction.

Parameters

thd	The THD session object used to process the detached XA transaction.

◆ cleanup_context()

void Sql_cmd_xa_second_phase::cleanup_context ( THD * thd ) const

protected

Cleans up the THD context in order to prepare it for re-use.

Execution is as follows:

The active THD session binlogging state is cleared.
Any MDL context backup, associated with the detached transaction, is deleted.
The detached transaction context is deleted from the transaction cache.
GTID state is finalized, either committing or rolling back the GTID information.

Parameters

thd	The THD session object used to process the detached XA transaction.

◆ dispose()

void Sql_cmd_xa_second_phase::dispose ( )

protected

Disposes of member variables that need it, because destructors for Sql_cmd classes aren't invoked (since they are created in the internal memory pool, memory is disposed as a all block).

◆ enter_commit_order()

bool Sql_cmd_xa_second_phase::enter_commit_order ( THD * thd )

protected

For replica applier threads, enters the wait on the commit order.

Execution is as follows:

Enters the wait on the commit order.
If the wait fails (timeout or possible deadlock found), resets the overall state to a point where a retry is possible: a. Resets the GTID infra-structure. b. Rolls back the MDL context to the recorded savepoint. c. Resets the transaction binlogging state.

Parameters

thd	The THD session object used to process the detached XA transaction.

Returns: false if the commit order wait was successful, true otherwise.

◆ exit_commit_order()

void Sql_cmd_xa_second_phase::exit_commit_order ( THD * thd ) const

protected

For replica applier threads, finishes the wait on the commit order and allows other threads to proceed.

Parameters

thd	The THD session object used to process the detached XA transaction.

◆ find_and_initialize_xa_context()

bool Sql_cmd_xa_second_phase::find_and_initialize_xa_context ( THD * thd )

protected

Tries to find and initialize the Transaction_ctx for the underlying detached XA transaction.

Execution is as follows:

Find transaction in the transaction cache.
Ensure that the underlying state regards the detached XA transaction.

Parameters

thd	The THD session object used to process the detached XA transaction.

Returns: false if the transaction context was successfully initialized, true otherwise.

◆ release_locks()

void Sql_cmd_xa_second_phase::release_locks ( ) const

protected

Release any locks acquires in acquire_locks still needing to be released.

◆ setup_thd_context()

void Sql_cmd_xa_second_phase::setup_thd_context ( THD * thd )

protected

Initializes the necessary parts of the thd parameter, transferring some of the detached XA transaction context to the active session.

This is necessary to use other parts of the infra-structure that rely on having the active THD session properly initialized.

Execution is as follows:

Determine if GTID infra-structure is consistent and ready to finalize the transaction.
Check the detached transaction status.
Transfer to the THD session object the state of the detached XA transaction w.r.t whether or not the transaction has already been binlogged.

Parameters

thd	The THD session object used to process the detached XA transaction.

Member Data Documentation

◆ m_detached_trx_context

std::shared_ptr<Transaction_ctx> Sql_cmd_xa_second_phase::m_detached_trx_context {nullptr}

protected

The detached transaction context, retrieved from the transaction cache.

◆ m_gtid_error

bool Sql_cmd_xa_second_phase::m_gtid_error {false}

protected

Whether or not the initialization of GTIDs returned an error.

◆ m_mdl_savepoint

MDL_savepoint Sql_cmd_xa_second_phase::m_mdl_savepoint

protected

The MDL savepoint used to rollback the MDL context when transient errors occur.

◆ m_need_clear_owned_gtid

bool Sql_cmd_xa_second_phase::m_need_clear_owned_gtid {false}

protected

Whether or not the OWNED_GTID related structures need to be cleaned.

◆ m_result

bool Sql_cmd_xa_second_phase::m_result {false}

protected

The incremental success of the several initialization and deinitialization steps.

Is mainly used to steer some of the deinitialization calls

◆ m_xid

xid_t* Sql_cmd_xa_second_phase::m_xid {nullptr}

protected

The XID associated with the underlying XA transaction.

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

sql/xa/sql_xa_second_phase.h
sql/xa/sql_xa_second_phase.cc

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ Sql_cmd_xa_second_phase()

◆ ~Sql_cmd_xa_second_phase()

Member Function Documentation

◆ acquire_locks()

◆ assign_xid_to_thd()

◆ cleanup_context()

◆ dispose()

◆ enter_commit_order()

◆ exit_commit_order()

◆ find_and_initialize_xa_context()

◆ release_locks()

◆ setup_thd_context()

Member Data Documentation

◆ m_detached_trx_context

◆ m_gtid_error

◆ m_mdl_savepoint

◆ m_need_clear_owned_gtid

◆ m_result

◆ m_xid