TLA  Line data    Source code

       1                 : /*-------------------------------------------------------------------------
       2                 :  *
       3                 :  * snapmgr.h
       4                 :  *    POSTGRES snapshot manager
       5                 :  *
       6                 :  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
       7                 :  * Portions Copyright (c) 1994, Regents of the University of California
       8                 :  *
       9                 :  * src/include/utils/snapmgr.h
      10                 :  *
      11                 :  *-------------------------------------------------------------------------
      12                 :  */
      13                 : #ifndef SNAPMGR_H
      14                 : #define SNAPMGR_H
      15                 : 
      16                 : #include "access/transam.h"
      17                 : #include "utils/relcache.h"
      18                 : #include "utils/resowner.h"
      19                 : #include "utils/snapshot.h"
      20                 : 
      21                 : 
      22                 : /*
      23                 :  * The structure used to map times to TransactionId values for the "snapshot
      24                 :  * too old" feature must have a few entries at the tail to hold old values;
      25                 :  * otherwise the lookup will often fail and the expected early pruning or
      26                 :  * vacuum will not usually occur.  It is best if this padding is for a number
      27                 :  * of minutes greater than a thread would normally be stalled, but it's OK if
      28                 :  * early vacuum opportunities are occasionally missed, so there's no need to
      29                 :  * use an extreme value or get too fancy.  10 minutes seems plenty.
      30                 :  */
      31                 : #define OLD_SNAPSHOT_PADDING_ENTRIES 10
      32                 : #define OLD_SNAPSHOT_TIME_MAP_ENTRIES (old_snapshot_threshold + OLD_SNAPSHOT_PADDING_ENTRIES)
      33                 : 
      34                 : /*
      35                 :  * Common definition of relation properties that allow early pruning/vacuuming
      36                 :  * when old_snapshot_threshold >= 0.
      37                 :  */
      38                 : #define RelationAllowsEarlyPruning(rel) \
      39                 : ( \
      40                 :      RelationIsPermanent(rel) && !IsCatalogRelation(rel) \
      41                 :   && !RelationIsAccessibleInLogicalDecoding(rel) \
      42                 : )
      43                 : 
      44                 : #define EarlyPruningEnabled(rel) (old_snapshot_threshold >= 0 && RelationAllowsEarlyPruning(rel))
      45                 : 
      46                 : /* GUC variables */
      47                 : extern PGDLLIMPORT int old_snapshot_threshold;
      48                 : 
      49                 : 
      50                 : extern Size SnapMgrShmemSize(void);
      51                 : extern void SnapMgrInit(void);
      52                 : extern TimestampTz GetSnapshotCurrentTimestamp(void);
      53                 : extern TimestampTz GetOldSnapshotThresholdTimestamp(void);
      54                 : extern void SnapshotTooOldMagicForTest(void);
      55                 : 
      56                 : extern PGDLLIMPORT bool FirstSnapshotSet;
      57                 : 
      58                 : extern PGDLLIMPORT TransactionId TransactionXmin;
      59                 : extern PGDLLIMPORT TransactionId RecentXmin;
      60                 : 
      61                 : /* Variables representing various special snapshot semantics */
      62                 : extern PGDLLIMPORT SnapshotData SnapshotSelfData;
      63                 : extern PGDLLIMPORT SnapshotData SnapshotAnyData;
      64                 : extern PGDLLIMPORT SnapshotData CatalogSnapshotData;
      65                 : 
      66                 : #define SnapshotSelf        (&SnapshotSelfData)
      67                 : #define SnapshotAny         (&SnapshotAnyData)
      68                 : 
      69                 : /*
      70                 :  * We don't provide a static SnapshotDirty variable because it would be
      71                 :  * non-reentrant.  Instead, users of that snapshot type should declare a
      72                 :  * local variable of type SnapshotData, and initialize it with this macro.
      73                 :  */
      74                 : #define InitDirtySnapshot(snapshotdata)  \
      75                 :     ((snapshotdata).snapshot_type = SNAPSHOT_DIRTY)
      76                 : 
      77                 : /*
      78                 :  * Similarly, some initialization is required for a NonVacuumable snapshot.
      79                 :  * The caller must supply the visibility cutoff state to use (c.f.
      80                 :  * GlobalVisTestFor()).
      81                 :  */
      82                 : #define InitNonVacuumableSnapshot(snapshotdata, vistestp)  \
      83                 :     ((snapshotdata).snapshot_type = SNAPSHOT_NON_VACUUMABLE, \
      84                 :      (snapshotdata).vistest = (vistestp))
      85                 : 
      86                 : /*
      87                 :  * Similarly, some initialization is required for SnapshotToast.  We need
      88                 :  * to set lsn and whenTaken correctly to support snapshot_too_old.
      89                 :  */
      90                 : #define InitToastSnapshot(snapshotdata, l, w)  \
      91                 :     ((snapshotdata).snapshot_type = SNAPSHOT_TOAST, \
      92                 :      (snapshotdata).lsn = (l),                  \
      93                 :      (snapshotdata).whenTaken = (w))
      94                 : 
      95                 : /* This macro encodes the knowledge of which snapshots are MVCC-safe */
      96                 : #define IsMVCCSnapshot(snapshot)  \
      97                 :     ((snapshot)->snapshot_type == SNAPSHOT_MVCC || \
      98                 :      (snapshot)->snapshot_type == SNAPSHOT_HISTORIC_MVCC)
      99                 : 
     100                 : #ifndef FRONTEND
     101                 : static inline bool
     102 CBC     9384962 : OldSnapshotThresholdActive(void)
     103                 : {
     104         9384962 :     return old_snapshot_threshold >= 0;
     105                 : }
     106                 : #endif
     107                 : 
     108                 : extern Snapshot GetTransactionSnapshot(void);
     109                 : extern Snapshot GetLatestSnapshot(void);
     110                 : extern void SnapshotSetCommandId(CommandId curcid);
     111                 : extern Snapshot GetOldestSnapshot(void);
     112                 : 
     113                 : extern Snapshot GetCatalogSnapshot(Oid relid);
     114                 : extern Snapshot GetNonHistoricCatalogSnapshot(Oid relid);
     115                 : extern void InvalidateCatalogSnapshot(void);
     116                 : extern void InvalidateCatalogSnapshotConditionally(void);
     117                 : 
     118                 : extern void PushActiveSnapshot(Snapshot snapshot);
     119                 : extern void PushActiveSnapshotWithLevel(Snapshot snapshot, int snap_level);
     120                 : extern void PushCopiedSnapshot(Snapshot snapshot);
     121                 : extern void UpdateActiveSnapshotCommandId(void);
     122                 : extern void PopActiveSnapshot(void);
     123                 : extern Snapshot GetActiveSnapshot(void);
     124                 : extern bool ActiveSnapshotSet(void);
     125                 : 
     126                 : extern Snapshot RegisterSnapshot(Snapshot snapshot);
     127                 : extern void UnregisterSnapshot(Snapshot snapshot);
     128                 : extern Snapshot RegisterSnapshotOnOwner(Snapshot snapshot, ResourceOwner owner);
     129                 : extern void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner);
     130                 : 
     131                 : extern void AtSubCommit_Snapshot(int level);
     132                 : extern void AtSubAbort_Snapshot(int level);
     133                 : extern void AtEOXact_Snapshot(bool isCommit, bool resetXmin);
     134                 : 
     135                 : extern void ImportSnapshot(const char *idstr);
     136                 : extern bool XactHasExportedSnapshots(void);
     137                 : extern void DeleteAllExportedSnapshotFiles(void);
     138                 : extern void WaitForOlderSnapshots(TransactionId limitXmin, bool progress);
     139                 : extern bool ThereAreNoPriorRegisteredSnapshots(void);
     140                 : extern bool HaveRegisteredOrActiveSnapshot(void);
     141                 : extern bool TransactionIdLimitedForOldSnapshots(TransactionId recentXmin,
     142                 :                                                 Relation relation,
     143                 :                                                 TransactionId *limit_xid,
     144                 :                                                 TimestampTz *limit_ts);
     145                 : extern void SetOldSnapshotThresholdTimestamp(TimestampTz ts, TransactionId xlimit);
     146                 : extern void MaintainOldSnapshotTimeMapping(TimestampTz whenTaken,
     147                 :                                            TransactionId xmin);
     148                 : 
     149                 : extern char *ExportSnapshot(Snapshot snapshot);
     150                 : 
     151                 : /*
     152                 :  * These live in procarray.c because they're intimately linked to the
     153                 :  * procarray contents, but thematically they better fit into snapmgr.h.
     154                 :  */
     155                 : typedef struct GlobalVisState GlobalVisState;
     156                 : extern GlobalVisState *GlobalVisTestFor(Relation rel);
     157                 : extern bool GlobalVisTestIsRemovableXid(GlobalVisState *state, TransactionId xid);
     158                 : extern bool GlobalVisTestIsRemovableFullXid(GlobalVisState *state, FullTransactionId fxid);
     159                 : extern FullTransactionId GlobalVisTestNonRemovableFullHorizon(GlobalVisState *state);
     160                 : extern TransactionId GlobalVisTestNonRemovableHorizon(GlobalVisState *state);
     161                 : extern bool GlobalVisCheckRemovableXid(Relation rel, TransactionId xid);
     162                 : extern bool GlobalVisCheckRemovableFullXid(Relation rel, FullTransactionId fxid);
     163                 : 
     164                 : /*
     165                 :  * Utility functions for implementing visibility routines in table AMs.
     166                 :  */
     167                 : extern bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot);
     168                 : 
     169                 : /* Support for catalog timetravel for logical decoding */
     170                 : struct HTAB;
     171                 : extern struct HTAB *HistoricSnapshotGetTupleCids(void);
     172                 : extern void SetupHistoricSnapshot(Snapshot historic_snapshot, struct HTAB *tuplecids);
     173                 : extern void TeardownHistoricSnapshot(bool is_error);
     174                 : extern bool HistoricSnapshotActive(void);
     175                 : 
     176                 : extern Size EstimateSnapshotSpace(Snapshot snapshot);
     177                 : extern void SerializeSnapshot(Snapshot snapshot, char *start_address);
     178                 : extern Snapshot RestoreSnapshot(char *start_address);
     179                 : extern void RestoreTransactionSnapshot(Snapshot snapshot, void *source_pgproc);
     180                 : 
     181                 : #endif                          /* SNAPMGR_H */