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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) 1996-2008, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.71 2008/01/01 19:45:59 momjian Exp $ * *------------------------------------------------------------------------- */ #ifndef TQUAL_H #define TQUAL_H #include "access/htup.h" #include "storage/buf.h" /* * We use SnapshotData structures to represent both "regular" (MVCC) * snapshots and "special" snapshots that have non-MVCC semantics. * The specific semantics of a snapshot are encoded by the "satisfies" * function. */ typedef struct SnapshotData *Snapshot; typedef bool (*SnapshotSatisfiesFunc) (HeapTupleHeader tuple, Snapshot snapshot, Buffer buffer); typedef struct SnapshotData { SnapshotSatisfiesFunc satisfies; /* tuple test function */ /* * The remaining fields are used only for MVCC snapshots, and are normally * just zeroes in special snapshots. (But xmin and xmax are used * specially by HeapTupleSatisfiesDirty.) * * An MVCC snapshot can never see the effects of XIDs >= xmax. It can see * the effects of all older XIDs except those listed in the snapshot. xmin * is stored as an optimization to avoid needing to search the XID arrays * for most tuples. */ TransactionId xmin; /* all XID < xmin are visible to me */ TransactionId xmax; /* all 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 */ int32 subxcnt; /* # of xact ids in subxip[], -1 if overflow */ TransactionId *subxip; /* array of subxact IDs in progress */ /* * note: all ids in subxip[] are >= xmin, but we don't bother filtering * out any that are >= xmax */ CommandId curcid; /* in my xact, CID < curcid are visible */ } SnapshotData; #define InvalidSnapshot ((Snapshot) NULL) /* 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) extern PGDLLIMPORT Snapshot SerializableSnapshot; extern PGDLLIMPORT Snapshot LatestSnapshot; extern PGDLLIMPORT 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. * 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 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; /* 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 void HeapTupleSetHintBits(HeapTupleHeader tuple, Buffer buffer, uint16 infomask, TransactionId xid); 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 */