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pg_include/utils/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) 1996-2012, 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);
+
+#endif   /* TQUAL_H */