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3e2f3c2e42
Previously, we tested for MVCC snapshots to see whether they were too old, but not TOAST snapshots, which can lead to complaints about missing TOAST chunks if those chunks are subject to early pruning. Ideally, the threshold lsn and timestamp for a TOAST snapshot would be that of the corresponding MVCC snapshot, but since we have no way of deciding which MVCC snapshot was used to fetch the TOAST pointer, use the oldest active or registered snapshot instead. Reported by Andres Freund, who also sketched out what the fix should look like. Patch by me, reviewed by Amit Kapila.
112 lines
4 KiB
C
112 lines
4 KiB
C
/*-------------------------------------------------------------------------
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*
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* snapmgr.h
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* POSTGRES snapshot manager
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*
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* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/snapmgr.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SNAPMGR_H
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#define SNAPMGR_H
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#include "fmgr.h"
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#include "utils/relcache.h"
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#include "utils/resowner.h"
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#include "utils/snapshot.h"
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/*
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* The structure used to map times to TransactionId values for the "snapshot
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* too old" feature must have a few entries at the tail to hold old values;
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* otherwise the lookup will often fail and the expected early pruning or
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* vacuum will not usually occur. It is best if this padding is for a number
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* of minutes greater than a thread would normally be stalled, but it's OK if
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* early vacuum opportunities are occasionally missed, so there's no need to
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* use an extreme value or get too fancy. 10 minutes seems plenty.
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*/
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#define OLD_SNAPSHOT_PADDING_ENTRIES 10
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#define OLD_SNAPSHOT_TIME_MAP_ENTRIES (old_snapshot_threshold + OLD_SNAPSHOT_PADDING_ENTRIES)
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/*
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* Common definition of relation properties that allow early pruning/vacuuming
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* when old_snapshot_threshold >= 0.
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*/
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#define RelationAllowsEarlyPruning(rel) \
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( \
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RelationNeedsWAL(rel) \
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&& !IsCatalogRelation(rel) \
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&& !RelationIsAccessibleInLogicalDecoding(rel) \
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&& !RelationHasUnloggedIndex(rel) \
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)
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#define EarlyPruningEnabled(rel) (old_snapshot_threshold >= 0 && RelationAllowsEarlyPruning(rel))
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/* GUC variables */
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extern PGDLLIMPORT int old_snapshot_threshold;
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extern Size SnapMgrShmemSize(void);
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extern void SnapMgrInit(void);
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extern int64 GetSnapshotCurrentTimestamp(void);
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extern int64 GetOldSnapshotThresholdTimestamp(void);
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extern bool FirstSnapshotSet;
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extern TransactionId TransactionXmin;
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extern TransactionId RecentXmin;
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extern TransactionId RecentGlobalXmin;
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extern TransactionId RecentGlobalDataXmin;
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extern Snapshot GetTransactionSnapshot(void);
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extern Snapshot GetLatestSnapshot(void);
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extern void SnapshotSetCommandId(CommandId curcid);
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extern Snapshot GetOldestSnapshot(void);
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extern Snapshot GetCatalogSnapshot(Oid relid);
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extern Snapshot GetNonHistoricCatalogSnapshot(Oid relid);
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extern void InvalidateCatalogSnapshot(void);
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extern void PushActiveSnapshot(Snapshot snapshot);
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extern void PushCopiedSnapshot(Snapshot snapshot);
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extern void UpdateActiveSnapshotCommandId(void);
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extern void PopActiveSnapshot(void);
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extern Snapshot GetActiveSnapshot(void);
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extern bool ActiveSnapshotSet(void);
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extern Snapshot RegisterSnapshot(Snapshot snapshot);
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extern void UnregisterSnapshot(Snapshot snapshot);
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extern Snapshot RegisterSnapshotOnOwner(Snapshot snapshot, ResourceOwner owner);
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extern void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner);
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extern void AtSubCommit_Snapshot(int level);
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extern void AtSubAbort_Snapshot(int level);
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extern void AtEOXact_Snapshot(bool isCommit);
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extern Datum pg_export_snapshot(PG_FUNCTION_ARGS);
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extern void ImportSnapshot(const char *idstr);
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extern bool XactHasExportedSnapshots(void);
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extern void DeleteAllExportedSnapshotFiles(void);
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extern bool ThereAreNoPriorRegisteredSnapshots(void);
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extern TransactionId TransactionIdLimitedForOldSnapshots(TransactionId recentXmin,
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Relation relation);
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extern void MaintainOldSnapshotTimeMapping(int64 whenTaken, TransactionId xmin);
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extern char *ExportSnapshot(Snapshot snapshot);
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/* Support for catalog timetravel for logical decoding */
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struct HTAB;
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extern struct HTAB *HistoricSnapshotGetTupleCids(void);
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extern void SetupHistoricSnapshot(Snapshot snapshot_now, struct HTAB *tuplecids);
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extern void TeardownHistoricSnapshot(bool is_error);
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extern bool HistoricSnapshotActive(void);
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extern Size EstimateSnapshotSpace(Snapshot snapshot);
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extern void SerializeSnapshot(Snapshot snapshot, char *start_address);
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extern Snapshot RestoreSnapshot(char *start_address);
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extern void RestoreTransactionSnapshot(Snapshot snapshot, void *master_pgproc);
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#endif /* SNAPMGR_H */
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