MVCC Class Reference

The MVCC read view manager. More...

#include <read0read.h>

Public Member Functions
	MVCC (ulint size)
	Constructor. More...
	~MVCC ()
	Destructor. More...
void	view_open (ReadView *&view, trx_t *trx)
	Allocate and create a view. More...
void	view_close (ReadView *&view, bool own_mutex)
	Close a view created by the above function. More...
void	view_release (ReadView *&view)
	Release a view that is inactive but not closed. More...
void	clone_oldest_view (ReadView *view)
	Clones the oldest view and stores it in view. More...
ulint	size () const

Static Public Member Functions
static bool	is_view_active (ReadView *view)
static void	set_view_creator_trx_id (ReadView *view, trx_id_t id)
	Set the view creator transaction id. More...

Private Member Functions
bool	validate () const
	Validates a read view list. More...
ReadView *	get_view ()
	Find a free view from the active list, if none found then allocate a new view. More...
ReadView *	get_oldest_view () const
	Get the oldest view in the system. More...
ReadView *	get_view_created_by_trx_id (trx_id_t trx_id) const
	MVCC (const MVCC &)
MVCC &	operator= (const MVCC &)
typedef	UT_LIST_BASE_NODE_T (ReadView, m_view_list) view_list_t

Private Attributes
view_list_t	m_free
	Free views ready for reuse. More...
view_list_t	m_views
	Active and closed views, the closed views will have the creator trx id set to TRX_ID_MAX. More...

Detailed Description

The MVCC read view manager.

Constructor & Destructor Documentation

MVCC() [1/2]

MVCC::MVCC ( ulint  size )

explicit

Constructor.

Parameters

size	Number of views to pre-allocate

~MVCC()

MVCC::~MVCC

(

)

Destructor.

Free all the views in the m_free list

MVCC() [2/2]

MVCC::MVCC ( const MVCC &  )

private

Member Function Documentation

clone_oldest_view()

void MVCC::clone_oldest_view

(

ReadView *

view

)

Clones the oldest view and stores it in view.

No need to call view_close(). The caller owns the view that is passed in. It will also move the closed views from the m_views list to the m_free list. This function is called by Purge to determine whether it should purge the delete marked record or not.

Parameters

view	Preallocated view, owned by the caller

get_oldest_view()

ReadView * MVCC::get_oldest_view ( ) const

inlineprivate

Get the oldest view in the system.

Get the oldest (active) view in the system.

It will also move the delete marked read views from the views list to the freed list.

Returns

oldest view if found or NULL

oldest view if found or NULL

get_view()

ReadView * MVCC::get_view ( )

inlineprivate

Find a free view from the active list, if none found then allocate a new view.

This function will also attempt to move delete marked views from the active list to the freed list.

Returns

a view to use

a view to use

get_view_created_by_trx_id()

ReadView * MVCC::get_view_created_by_trx_id ( trx_id_t  trx_id ) const

private

is_view_active()

static bool MVCC::is_view_active ( ReadView *  view )

inlinestatic

Returns

true if the view is active and valid

operator=()

MVCC & MVCC::operator= ( const MVCC &  )

private

set_view_creator_trx_id()

static void MVCC::set_view_creator_trx_id ( ReadView *  view, trx_id_t  id  )

inlinestatic

Set the view creator transaction id.

Note: This should be set only for views created by RW transactions.

Parameters

view	Set the creator trx id for this view
id	Transaction id to set

size()

ulint MVCC::size

(

)

const

Returns

the number of active views

UT_LIST_BASE_NODE_T()

typedef MVCC::UT_LIST_BASE_NODE_T ( ReadView  , m_view_list    )

private

validate()

bool MVCC::validate ( ) const

private

Validates a read view list.

view_close()

void MVCC::view_close	(	ReadView *&	view,
		bool	own_mutex
	)

Close a view created by the above function.

Parameters

view	view allocated by trx_open.
own_mutex	true if caller owns trx_sys_t::mutex

view_open()

void MVCC::view_open	(	ReadView *&	view,
		trx_t *	trx
	)

Allocate and create a view.

Parameters

view	View owned by this class created for the caller. Must be freed by calling view_close()
trx	Transaction instance of caller

If no new RW transaction has been started since the last view was created then reuse the the existing view.

view_release()

void MVCC::view_release

(

ReadView *&

view

)

Release a view that is inactive but not closed.

Caller must own the trx_sys_t::mutex.

Parameters

view	View to release

RW transactions should not free their views here. Their views should freed using view_close_view()

Member Data Documentation

m_free

view_list_t MVCC::m_free

private

Free views ready for reuse.

m_views

view_list_t MVCC::m_views

private

Active and closed views, the closed views will have the creator trx id set to TRX_ID_MAX.

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

• storage/innobase/include/read0read.h
• storage/innobase/read/read0read.cc