tqual.h

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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) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/tqual.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef TQUAL_H
#define TQUAL_H

#include "utils/snapshot.h"


/* Static variables representing various special snapshot semantics */
extern PGDLLIMPORT SnapshotData SnapshotNowData;
extern PGDLLIMPORT SnapshotData SnapshotSelfData;
extern PGDLLIMPORT SnapshotData SnapshotAnyData;
extern PGDLLIMPORT SnapshotData SnapshotToastData;

#define SnapshotNow         (&SnapshotNowData)
#define SnapshotSelf        (&SnapshotSelfData)
#define SnapshotAny         (&SnapshotAnyData)
#define SnapshotToast       (&SnapshotToastData)

/*
 * We don't provide a static SnapshotDirty variable because it would be
 * non-reentrant.  Instead, users of that snapshot type should declare a
 * local variable of type SnapshotData, and initialize it with this macro.
 */
#define InitDirtySnapshot(snapshotdata)  \
    ((snapshotdata).satisfies = HeapTupleSatisfiesDirty)

/* This macro encodes the knowledge of which snapshots are MVCC-safe */
#define IsMVCCSnapshot(snapshot)  \
    ((snapshot)->satisfies == HeapTupleSatisfiesMVCC)

/*
 * HeapTupleSatisfiesVisibility
 *      True iff heap tuple satisfies a time qual.
 *
 * Notes:
 *  Assumes heap tuple is valid.
 *  Beware of multiple evaluations of snapshot argument.
 *  Hint bits in the HeapTuple's t_infomask may be updated as a side effect;
 *  if so, the indicated buffer is marked dirty.
 */
#define HeapTupleSatisfiesVisibility(tuple, snapshot, buffer) \
    ((*(snapshot)->satisfies) ((tuple)->t_data, snapshot, buffer))

/* 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;

/* These are the "satisfies" test routines for the various snapshot types */
extern bool HeapTupleSatisfiesMVCC(HeapTupleHeader tuple,
                       Snapshot snapshot, Buffer buffer);
extern bool HeapTupleSatisfiesNow(HeapTupleHeader tuple,
                      Snapshot snapshot, Buffer buffer);
extern bool HeapTupleSatisfiesSelf(HeapTupleHeader tuple,
                       Snapshot snapshot, Buffer buffer);
extern bool HeapTupleSatisfiesAny(HeapTupleHeader tuple,
                      Snapshot snapshot, Buffer buffer);
extern bool HeapTupleSatisfiesToast(HeapTupleHeader tuple,
                        Snapshot snapshot, Buffer buffer);
extern bool HeapTupleSatisfiesDirty(HeapTupleHeader tuple,
                        Snapshot snapshot, Buffer buffer);

/* Special "satisfies" routines with different APIs */
extern HTSU_Result HeapTupleSatisfiesUpdate(HeapTupleHeader tuple,
                         CommandId curcid, Buffer buffer);
extern HTSV_Result HeapTupleSatisfiesVacuum(HeapTupleHeader tuple,
                         TransactionId OldestXmin, Buffer buffer);
extern bool HeapTupleIsSurelyDead(HeapTupleHeader tuple,
                      TransactionId OldestXmin);

extern void HeapTupleSetHintBits(HeapTupleHeader tuple, Buffer buffer,
                     uint16 infomask, TransactionId xid);
extern bool HeapTupleHeaderIsOnlyLocked(HeapTupleHeader tuple);

#endif   /* TQUAL_H */