src/include/utils/tqual.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * tqual.h
   4  *        POSTGRES "time" qualification definitions.
   5  *
   6  *        Should be moved/renamed...    - vadim 07/28/98
   7  *
   8  * Copyright (c) 1994, Regents of the University of California
   9  *
  10  * $Id: tqual.h,v 1.21 1999/05/25 16:14:58 momjian Exp $
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef TQUAL_H
  15 #define TQUAL_H
  16
  17 #include <access/htup.h>
  18
  19 typedef struct SnapshotData
  20 {
  21         TransactionId xmin;                     /* XID < xmin are visible to me */
  22         TransactionId xmax;                     /* XID >= xmax are invisible to me */
  23         uint32          xcnt;                   /* # of xact below */
  24         TransactionId *xip;                     /* array of xacts in progress */
  25         ItemPointerData tid;            /* required for Dirty snapshot -:( */
  26 }                       SnapshotData;
  27
  28 typedef SnapshotData *Snapshot;
  29
  30 #define SnapshotNow                                     ((Snapshot) 0x0)
  31 #define SnapshotSelf                            ((Snapshot) 0x1)
  32
  33 extern Snapshot SnapshotDirty;
  34 extern Snapshot QuerySnapshot;
  35 extern Snapshot SerializableSnapshot;
  36
  37 #define IsSnapshotNow(snapshot)         ((Snapshot) snapshot == SnapshotNow)
  38 #define IsSnapshotSelf(snapshot)        ((Snapshot) snapshot == SnapshotSelf)
  39 #define IsSnapshotDirty(snapshot)       ((Snapshot) snapshot == SnapshotDirty)
  40
  41 extern TransactionId HeapSpecialTransactionId;
  42 extern CommandId HeapSpecialCommandId;
  43
  44 /*
  45  * HeapTupleSatisfiesVisibility
  46  *              True iff heap tuple satsifies a time qual.
  47  *
  48  * Note:
  49  *              Assumes heap tuple is valid.
  50  */
  51 #define HeapTupleSatisfiesVisibility(tuple, snapshot) \
  52 ( \
  53         TransactionIdEquals((tuple)->t_data->t_xmax, AmiTransactionId) ? \
  54                 false \
  55         : \
  56         ( \
  57                 (IsSnapshotSelf(snapshot) || heapisoverride()) ? \
  58                         HeapTupleSatisfiesItself((tuple)->t_data) \
  59                 : \
  60                         ((IsSnapshotDirty(snapshot)) ? \
  61                                 HeapTupleSatisfiesDirty((tuple)->t_data) \
  62                         : \
  63                                 ((IsSnapshotNow(snapshot)) ? \
  64                                         HeapTupleSatisfiesNow((tuple)->t_data) \
  65                                 : \
  66                                         HeapTupleSatisfiesSnapshot((tuple)->t_data, snapshot) \
  67                                 ) \
  68                         ) \
  69         ) \
  70 )
  71
  72 #define heapisoverride() \
  73 ( \
  74         (!TransactionIdIsValid(HeapSpecialTransactionId)) ? \
  75                 false \
  76         : \
  77         ( \
  78                 (!TransactionIdEquals(GetCurrentTransactionId(), \
  79                                                          HeapSpecialTransactionId) || \
  80                  GetCurrentCommandId() != HeapSpecialCommandId) ? \
  81                 ( \
  82                         HeapSpecialTransactionId = InvalidTransactionId, \
  83                         false \
  84                 ) \
  85                 : \
  86                         true \
  87         ) \
  88 )
  89
  90 #define HeapTupleMayBeUpdated           0
  91 #define HeapTupleInvisible                      1
  92 #define HeapTupleSelfUpdated            2
  93 #define HeapTupleUpdated                        3
  94 #define HeapTupleBeingUpdated           4
  95
  96 extern bool HeapTupleSatisfiesItself(HeapTupleHeader tuple);
  97 extern bool HeapTupleSatisfiesNow(HeapTupleHeader tuple);
  98 extern bool HeapTupleSatisfiesDirty(HeapTupleHeader tuple);
  99 extern bool HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot);
 100 extern int      HeapTupleSatisfiesUpdate(HeapTuple tuple);
 101
 102 extern void setheapoverride(bool on);
 103
 104 extern Snapshot GetSnapshotData(bool serializable);
 105 extern void SetQuerySnapshot(void);
 106 extern void FreeXactSnapshot(void);
 107
 108 #endif   /* TQUAL_H */