multixact.h

Go to the documentation of this file.

/*
 * multixact.h
 *
 * PostgreSQL multi-transaction-log manager
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/multixact.h
 */
#ifndef MULTIXACT_H
#define MULTIXACT_H

#include "access/xlogreader.h"
#include "lib/stringinfo.h"


/*
 * The first two MultiXactId values are reserved to store the truncation Xid
 * and epoch of the first segment, so we start assigning multixact values from
 * 2.
 */
#define InvalidMultiXactId  ((MultiXactId) 0)
#define FirstMultiXactId    ((MultiXactId) 1)
#define MaxMultiXactId      ((MultiXactId) 0xFFFFFFFF)

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

#define MaxMultiXactOffset  ((MultiXactOffset) 0xFFFFFFFF)

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

/*
 * Possible multixact lock modes ("status").  The first four modes are for
 * tuple locks (FOR KEY SHARE, FOR SHARE, FOR NO KEY UPDATE, FOR UPDATE); the
 * next two are used for update and delete modes.
 */
typedef enum
{
    MultiXactStatusForKeyShare = 0x00,
    MultiXactStatusForShare = 0x01,
    MultiXactStatusForNoKeyUpdate = 0x02,
    MultiXactStatusForUpdate = 0x03,
    /* an update that doesn't touch "key" columns */
    MultiXactStatusNoKeyUpdate = 0x04,
    /* other updates, and delete */
    MultiXactStatusUpdate = 0x05
} MultiXactStatus;

#define MaxMultiXactStatus MultiXactStatusUpdate

/* does a status value correspond to a tuple update? */
#define ISUPDATE_from_mxstatus(status) \
            ((status) > MultiXactStatusForUpdate)


typedef struct MultiXactMember
{
    TransactionId xid;
    MultiXactStatus status;
} MultiXactMember;


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

#define XLOG_MULTIXACT_ZERO_OFF_PAGE    0x00
#define XLOG_MULTIXACT_ZERO_MEM_PAGE    0x10
#define XLOG_MULTIXACT_CREATE_ID        0x20
#define XLOG_MULTIXACT_TRUNCATE_ID      0x30

typedef struct xl_multixact_create
{
    MultiXactId mid;            /* new MultiXact's ID */
    MultiXactOffset moff;       /* its starting offset in members file */
    int32       nmembers;       /* number of member XIDs */
    MultiXactMember members[FLEXIBLE_ARRAY_MEMBER];
} xl_multixact_create;

#define SizeOfMultiXactCreate (offsetof(xl_multixact_create, members))

typedef struct xl_multixact_truncate
{
    Oid         oldestMultiDB;

    /* to-be-truncated range of multixact offsets */
    MultiXactId startTruncOff;  /* just for completeness' sake */
    MultiXactId endTruncOff;

    /* to-be-truncated range of multixact members */
    MultiXactOffset startTruncMemb;
    MultiXactOffset endTruncMemb;
} xl_multixact_truncate;

#define SizeOfMultiXactTruncate (sizeof(xl_multixact_truncate))


extern MultiXactId MultiXactIdCreate(TransactionId xid1,
                                     MultiXactStatus status1, TransactionId xid2,
                                     MultiXactStatus status2);
extern MultiXactId MultiXactIdExpand(MultiXactId multi, TransactionId xid,
                                     MultiXactStatus status);
extern MultiXactId MultiXactIdCreateFromMembers(int nmembers,
                                                MultiXactMember *members);

extern MultiXactId ReadNextMultiXactId(void);
extern bool MultiXactIdIsRunning(MultiXactId multi, bool isLockOnly);
extern void MultiXactIdSetOldestMember(void);
extern int  GetMultiXactIdMembers(MultiXactId multi, MultiXactMember **xids,
                                  bool allow_old, bool isLockOnly);
extern bool MultiXactIdPrecedes(MultiXactId multi1, MultiXactId multi2);
extern bool MultiXactIdPrecedesOrEquals(MultiXactId multi1,
                                        MultiXactId multi2);

extern void AtEOXact_MultiXact(void);
extern void AtPrepare_MultiXact(void);
extern void PostPrepare_MultiXact(TransactionId xid);

extern Size MultiXactShmemSize(void);
extern void MultiXactShmemInit(void);
extern void BootStrapMultiXact(void);
extern void StartupMultiXact(void);
extern void TrimMultiXact(void);
extern void ShutdownMultiXact(void);
extern void SetMultiXactIdLimit(MultiXactId oldest_datminmxid,
                                Oid oldest_datoid,
                                bool is_startup);
extern void MultiXactGetCheckptMulti(bool is_shutdown,
                                     MultiXactId *nextMulti,
                                     MultiXactOffset *nextMultiOffset,
                                     MultiXactId *oldestMulti,
                                     Oid *oldestMultiDB);
extern void CheckPointMultiXact(void);
extern MultiXactId GetOldestMultiXactId(void);
extern void TruncateMultiXact(MultiXactId oldestMulti, Oid oldestMultiDB);
extern void MultiXactSetNextMXact(MultiXactId nextMulti,
                                  MultiXactOffset nextMultiOffset);
extern void MultiXactAdvanceNextMXact(MultiXactId minMulti,
                                      MultiXactOffset minMultiOffset);
extern void MultiXactAdvanceOldest(MultiXactId oldestMulti, Oid oldestMultiDB);
extern int  MultiXactMemberFreezeThreshold(void);

extern void multixact_twophase_recover(TransactionId xid, uint16 info,
                                       void *recdata, uint32 len);
extern void multixact_twophase_postcommit(TransactionId xid, uint16 info,
                                          void *recdata, uint32 len);
extern void multixact_twophase_postabort(TransactionId xid, uint16 info,
                                         void *recdata, uint32 len);

extern void multixact_redo(XLogReaderState *record);
extern void multixact_desc(StringInfo buf, XLogReaderState *record);
extern const char *multixact_identify(uint8 info);
extern char *mxid_to_string(MultiXactId multi, int nmembers,
                            MultiXactMember *members);

#endif                          /* MULTIXACT_H */