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/*-------------------------------------------------------------------------
*
* tqual.h
* POSTGRES "time qualification" definitions, ie, tuple visibility rules.
*
* Should be moved/renamed... - vadim 07/28/98
*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.59 2005/10/15 02:49:46 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef TQUAL_H
#define TQUAL_H
#include "access/htup.h"
#include "access/xact.h"
#include "storage/buf.h"
/*
* "Regular" snapshots are pointers to a SnapshotData structure.
*
* We also have some "special" snapshot values that have fixed meanings
* and don't need any backing SnapshotData. These are encoded by small
* integer values, which of course is a gross violation of ANSI C, but
* it works fine on all known platforms.
*
* SnapshotDirty is an even more special case: its semantics are fixed,
* but there is a backing SnapshotData struct for it. That struct is
* actually used as *output* data from tqual.c, not input into it.
* (But hey, SnapshotDirty ought to have a dirty implementation, no? ;-))
*/
typedef struct SnapshotData
{
TransactionId xmin; /* XID < xmin are visible to me */
TransactionId xmax; /* XID >= xmax are invisible to me */
uint32 xcnt; /* # of xact ids in xip[] */
TransactionId *xip; /* array of xact IDs in progress */
/* note: all ids in xip[] satisfy xmin <= xip[i] < xmax */
CommandId curcid; /* in my xact, CID < curcid are visible */
} SnapshotData;
typedef SnapshotData *Snapshot;
/* Special snapshot values: */
#define InvalidSnapshot ((Snapshot) 0x0) /* same as NULL */
#define SnapshotNow ((Snapshot) 0x1)
#define SnapshotSelf ((Snapshot) 0x2)
#define SnapshotAny ((Snapshot) 0x3)
#define SnapshotToast ((Snapshot) 0x4)
extern DLLIMPORT Snapshot SnapshotDirty;
extern DLLIMPORT Snapshot SerializableSnapshot;
extern DLLIMPORT Snapshot LatestSnapshot;
extern DLLIMPORT Snapshot ActiveSnapshot;
extern TransactionId TransactionXmin;
extern TransactionId RecentXmin;
extern TransactionId RecentGlobalXmin;
/*
* HeapTupleSatisfiesVisibility
* True iff heap tuple satisfies a time qual.
*
* Notes:
* Assumes heap tuple is valid.
* Beware of multiple evaluations of snapshot argument.
*/
#define HeapTupleSatisfiesVisibility(tuple, snapshot, buffer) \
((snapshot) == SnapshotNow ? \
HeapTupleSatisfiesNow((tuple)->t_data, buffer) \
: \
((snapshot) == SnapshotSelf ? \
HeapTupleSatisfiesItself((tuple)->t_data, buffer) \
: \
((snapshot) == SnapshotAny ? \
true \
: \
((snapshot) == SnapshotToast ? \
HeapTupleSatisfiesToast((tuple)->t_data, buffer) \
: \
((snapshot) == SnapshotDirty ? \
HeapTupleSatisfiesDirty((tuple)->t_data, buffer) \
: \
HeapTupleSatisfiesSnapshot((tuple)->t_data, snapshot, buffer) \
) \
) \
) \
) \
)
/* Result codes for HeapTupleSatisfiesUpdate */
typedef enum
{
HeapTupleMayBeUpdated,
HeapTupleInvisible,
HeapTupleSelfUpdated,
HeapTupleUpdated,
HeapTupleBeingUpdated
} HTSU_Result;
/* Result codes for HeapTupleSatisfiesVacuum */
typedef enum
{
HEAPTUPLE_DEAD, /* tuple is dead and deletable */
HEAPTUPLE_LIVE, /* tuple is live (committed, no deleter) */
HEAPTUPLE_RECENTLY_DEAD, /* tuple is dead, but not deletable yet */
HEAPTUPLE_INSERT_IN_PROGRESS, /* inserting xact is still in progress */
HEAPTUPLE_DELETE_IN_PROGRESS /* deleting xact is still in progress */
} HTSV_Result;
extern bool HeapTupleSatisfiesItself(HeapTupleHeader tuple, Buffer buffer);
extern bool HeapTupleSatisfiesNow(HeapTupleHeader tuple, Buffer buffer);
extern bool HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer);
extern bool HeapTupleSatisfiesToast(HeapTupleHeader tuple, Buffer buffer);
extern bool HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple,
Snapshot snapshot, Buffer buffer);
extern HTSU_Result HeapTupleSatisfiesUpdate(HeapTupleHeader tuple,
CommandId curcid, Buffer buffer);
extern HTSV_Result HeapTupleSatisfiesVacuum(HeapTupleHeader tuple,
TransactionId OldestXmin, Buffer buffer);
extern Snapshot GetTransactionSnapshot(void);
extern Snapshot GetLatestSnapshot(void);
extern Snapshot CopySnapshot(Snapshot snapshot);
extern void FreeSnapshot(Snapshot snapshot);
extern void FreeXactSnapshot(void);
/* in procarray.c; declared here to avoid including tqual.h in procarray.h: */
extern Snapshot GetSnapshotData(Snapshot snapshot, bool serializable);
#endif /* TQUAL_H */
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