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/*****************************************************************************
Copyright (c) 1997, 2013, Oracle and/or its affiliates. All Rights Reserved.
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
*****************************************************************************/
/**************************************************//**
@file include/read0read.h
Cursor read
Created 2/16/1997 Heikki Tuuri
*******************************************************/
#ifndef read0read_h
#define read0read_h
#include "read0types.h"
#include <algorithm>
/** The MVCC read view manager */
class MVCC {
public:
/** Constructor
@param size Number of views to pre-allocate */
explicit MVCC(ulint size);
/** Destructor.
Free all the views in the m_free list */
~MVCC();
/**
Allocate and create a view.
@param view view owned by this class created for the
caller. Must be freed by calling close()
@param trx transaction creating the view */
void view_open(ReadView*& view, trx_t* trx);
/**
Close a view created by the above function.
@para view view allocated by trx_open.
@param own_mutex true if caller owns trx_sys_t::mutex */
void view_close(ReadView*& view, bool own_mutex);
/**
Release a view that is inactive but not closed. Caller must own
the trx_sys_t::mutex.
@param view View to release */
void view_release(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 create it view.
@param view Preallocated view, owned by the caller */
void clone_oldest_view(ReadView* view);
/**
@return the number of active views */
ulint size() const;
/**
@return true if the view is active and valid */
static bool is_view_active(ReadView* view)
{
ut_a(view != reinterpret_cast<ReadView*>(0x1));
return(view != NULL && !(intptr_t(view) & 0x1));
}
/**
Set the view creator transaction id. Note: This shouldbe set only
for views created by RW transactions. */
static void set_view_creator_trx_id(ReadView* view, trx_id_t id);
private:
/**
Validates a read view list. */
bool validate() const;
/**
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.
@return a view to use */
inline ReadView* get_view();
/**
Get the oldest view in the system. It will also move the delete
marked read views from the views list to the freed list.
@return oldest view if found or NULL */
inline ReadView* get_oldest_view() const;
private:
// Prevent copying
MVCC(const MVCC&);
MVCC& operator=(const MVCC&);
private:
typedef UT_LIST_BASE_NODE_T(ReadView) view_list_t;
/** Free views ready for reuse. */
view_list_t m_free;
/** Active and closed views, the closed views will have the
creator trx id set to TRX_ID_MAX */
view_list_t m_views;
};
#endif /* read0read_h */
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