/*
 * multixact.h
 *
 * PostgreSQL multi-transaction-log manager
 *
 * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/include/access/multixact.h,v 1.12 2007/01/05 22:19:51 momjian Exp $
 */
#ifndef MULTIXACT_H
#define MULTIXACT_H

#include "access/xlog.h"

#define InvalidMultiXactId	((MultiXactId) 0)
#define FirstMultiXactId	((MultiXactId) 1)

#define MultiXactIdIsValid(multi) ((multi) != InvalidMultiXactId)

/* Number of SLRU buffers to use for multixact */
#define NUM_MXACTOFFSET_BUFFERS		8
#define NUM_MXACTMEMBER_BUFFERS		16

/* ----------------
 *		multixact-related XLOG entries
 * ----------------
 */

#define XLOG_MULTIXACT_ZERO_OFF_PAGE	0x00
#define XLOG_MULTIXACT_ZERO_MEM_PAGE	0x10
#define XLOG_MULTIXACT_CREATE_ID		0x20

typedef struct xl_multixact_create
{
	MultiXactId mid;			/* new MultiXact's ID */
	MultiXactOffset moff;		/* its starting offset in members file */
	int32		nxids;			/* number of member XIDs */
	TransactionId xids[1];		/* VARIABLE LENGTH ARRAY */
} xl_multixact_create;

#define MinSizeOfMultiXactCreate offsetof(xl_multixact_create, xids)


extern MultiXactId MultiXactIdCreate(TransactionId xid1, TransactionId xid2);
extern MultiXactId MultiXactIdExpand(MultiXactId multi, TransactionId xid);
extern bool MultiXactIdIsRunning(MultiXactId multi);
extern bool MultiXactIdIsCurrent(MultiXactId multi);
extern void MultiXactIdWait(MultiXactId multi);
extern bool ConditionalMultiXactIdWait(MultiXactId multi);
extern void MultiXactIdSetOldestMember(void);
extern int	GetMultiXactIdMembers(MultiXactId multi, TransactionId **xids);

extern void AtEOXact_MultiXact(void);

extern Size MultiXactShmemSize(void);
extern void MultiXactShmemInit(void);
extern void BootStrapMultiXact(void);
extern void StartupMultiXact(void);
extern void ShutdownMultiXact(void);
extern void MultiXactGetCheckptMulti(bool is_shutdown,
						 MultiXactId *nextMulti,
						 MultiXactOffset *nextMultiOffset);
extern void CheckPointMultiXact(void);
extern void MultiXactSetNextMXact(MultiXactId nextMulti,
					  MultiXactOffset nextMultiOffset);
extern void MultiXactAdvanceNextMXact(MultiXactId minMulti,
						  MultiXactOffset minMultiOffset);

extern void multixact_redo(XLogRecPtr lsn, XLogRecord *record);
extern void multixact_desc(StringInfo buf, uint8 xl_info, char *rec);

#endif   /* MULTIXACT_H */