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/*------------------------------------------------------------------------- * * snapmgr.h * POSTGRES snapshot manager * * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/include/utils/snapmgr.h * *------------------------------------------------------------------------- */ #ifndef SNAPMGR_H #define SNAPMGR_H #include "fmgr.h" #include "utils/relcache.h" #include "utils/resowner.h" #include "utils/snapshot.h" /* * The structure used to map times to TransactionId values for the "snapshot * too old" feature must have a few entries at the tail to hold old values; * otherwise the lookup will often fail and the expected early pruning or * vacuum will not usually occur. It is best if this padding is for a number * of minutes greater than a thread would normally be stalled, but it's OK if * early vacuum opportunities are occasionally missed, so there's no need to * use an extreme value or get too fancy. 10 minutes seems plenty. */ #define OLD_SNAPSHOT_PADDING_ENTRIES 10 #define OLD_SNAPSHOT_TIME_MAP_ENTRIES (old_snapshot_threshold + OLD_SNAPSHOT_PADDING_ENTRIES) /* * Common definition of relation properties that allow early pruning/vacuuming * when old_snapshot_threshold >= 0. */ #define RelationAllowsEarlyPruning(rel) \ ( \ RelationNeedsWAL(rel) \ && !IsCatalogRelation(rel) \ && !RelationIsAccessibleInLogicalDecoding(rel) \ && !RelationHasUnloggedIndex(rel) \ ) #define EarlyPruningEnabled(rel) (old_snapshot_threshold >= 0 && RelationAllowsEarlyPruning(rel)) /* GUC variables */ extern PGDLLIMPORT int old_snapshot_threshold; extern Size SnapMgrShmemSize(void); extern void SnapMgrInit(void); extern int64 GetSnapshotCurrentTimestamp(void); extern int64 GetOldSnapshotThresholdTimestamp(void); extern bool FirstSnapshotSet; extern PGDLLIMPORT TransactionId TransactionXmin; extern PGDLLIMPORT TransactionId RecentXmin; extern PGDLLIMPORT TransactionId RecentGlobalXmin; extern PGDLLIMPORT TransactionId RecentGlobalDataXmin; extern Snapshot GetTransactionSnapshot(void); extern Snapshot GetLatestSnapshot(void); extern void SnapshotSetCommandId(CommandId curcid); extern Snapshot GetOldestSnapshot(void); extern Snapshot GetCatalogSnapshot(Oid relid); extern Snapshot GetNonHistoricCatalogSnapshot(Oid relid); extern void InvalidateCatalogSnapshot(void); extern void InvalidateCatalogSnapshotConditionally(void); extern void PushActiveSnapshot(Snapshot snapshot); extern void PushCopiedSnapshot(Snapshot snapshot); extern void UpdateActiveSnapshotCommandId(void); extern void PopActiveSnapshot(void); extern Snapshot GetActiveSnapshot(void); extern bool ActiveSnapshotSet(void); extern Snapshot RegisterSnapshot(Snapshot snapshot); extern void UnregisterSnapshot(Snapshot snapshot); extern Snapshot RegisterSnapshotOnOwner(Snapshot snapshot, ResourceOwner owner); extern void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner); extern void AtSubCommit_Snapshot(int level); extern void AtSubAbort_Snapshot(int level); extern void AtEOXact_Snapshot(bool isCommit); extern Datum pg_export_snapshot(PG_FUNCTION_ARGS); extern void ImportSnapshot(const char *idstr); extern bool XactHasExportedSnapshots(void); extern void DeleteAllExportedSnapshotFiles(void); extern bool ThereAreNoPriorRegisteredSnapshots(void); extern TransactionId TransactionIdLimitedForOldSnapshots(TransactionId recentXmin, Relation relation); extern void MaintainOldSnapshotTimeMapping(int64 whenTaken, TransactionId xmin); extern char *ExportSnapshot(Snapshot snapshot); /* Support for catalog timetravel for logical decoding */ struct HTAB; extern struct HTAB *HistoricSnapshotGetTupleCids(void); extern void SetupHistoricSnapshot(Snapshot snapshot_now, struct HTAB *tuplecids); extern void TeardownHistoricSnapshot(bool is_error); extern bool HistoricSnapshotActive(void); extern Size EstimateSnapshotSpace(Snapshot snapshot); extern void SerializeSnapshot(Snapshot snapshot, char *start_address); extern Snapshot RestoreSnapshot(char *start_address); extern void RestoreTransactionSnapshot(Snapshot snapshot, void *master_pgproc); #endif /* SNAPMGR_H */