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snapmgr.h
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1 /*-------------------------------------------------------------------------
2  *
3  * snapmgr.h
4  * POSTGRES snapshot manager
5  *
6  * Portions Copyright (c) 1996-2022, 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 */
48 
49 
50 extern Size SnapMgrShmemSize(void);
51 extern void SnapMgrInit(void);
54 extern void SnapshotTooOldMagicForTest(void);
55 
56 extern PGDLLIMPORT bool FirstSnapshotSet;
57 
60 
61 /* Variables representing various special snapshot semantics */
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 static inline bool
102 {
103  return old_snapshot_threshold >= 0;
104 }
105 
106 extern Snapshot GetTransactionSnapshot(void);
107 extern Snapshot GetLatestSnapshot(void);
108 extern void SnapshotSetCommandId(CommandId curcid);
109 extern Snapshot GetOldestSnapshot(void);
110 
111 extern Snapshot GetCatalogSnapshot(Oid relid);
113 extern void InvalidateCatalogSnapshot(void);
115 
116 extern void PushActiveSnapshot(Snapshot snapshot);
117 extern void PushActiveSnapshotWithLevel(Snapshot snapshot, int snap_level);
118 extern void PushCopiedSnapshot(Snapshot snapshot);
119 extern void UpdateActiveSnapshotCommandId(void);
120 extern void PopActiveSnapshot(void);
121 extern Snapshot GetActiveSnapshot(void);
122 extern bool ActiveSnapshotSet(void);
123 
124 extern Snapshot RegisterSnapshot(Snapshot snapshot);
125 extern void UnregisterSnapshot(Snapshot snapshot);
127 extern void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner);
128 
129 extern void AtSubCommit_Snapshot(int level);
130 extern void AtSubAbort_Snapshot(int level);
131 extern void AtEOXact_Snapshot(bool isCommit, bool resetXmin);
132 
133 extern void ImportSnapshot(const char *idstr);
134 extern bool XactHasExportedSnapshots(void);
135 extern void DeleteAllExportedSnapshotFiles(void);
136 extern void WaitForOlderSnapshots(TransactionId limitXmin, bool progress);
137 extern bool ThereAreNoPriorRegisteredSnapshots(void);
138 extern bool HaveRegisteredOrActiveSnapshot(void);
140  Relation relation,
141  TransactionId *limit_xid,
142  TimestampTz *limit_ts);
144 extern void MaintainOldSnapshotTimeMapping(TimestampTz whenTaken,
145  TransactionId xmin);
146 
147 extern char *ExportSnapshot(Snapshot snapshot);
148 
149 /*
150  * These live in procarray.c because they're intimately linked to the
151  * procarray contents, but thematically they better fit into snapmgr.h.
152  */
153 typedef struct GlobalVisState GlobalVisState;
161 
162 /*
163  * Utility functions for implementing visibility routines in table AMs.
164  */
165 extern bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot);
166 
167 /* Support for catalog timetravel for logical decoding */
168 struct HTAB;
169 extern struct HTAB *HistoricSnapshotGetTupleCids(void);
170 extern void SetupHistoricSnapshot(Snapshot snapshot_now, struct HTAB *tuplecids);
171 extern void TeardownHistoricSnapshot(bool is_error);
172 extern bool HistoricSnapshotActive(void);
173 
174 extern Size EstimateSnapshotSpace(Snapshot snapshot);
175 extern void SerializeSnapshot(Snapshot snapshot, char *start_address);
176 extern Snapshot RestoreSnapshot(char *start_address);
177 extern void RestoreTransactionSnapshot(Snapshot snapshot, void *source_pgproc);
178 
179 #endif /* SNAPMGR_H */
#define PGDLLIMPORT
Definition: c.h:1331
uint32 CommandId
Definition: c.h:601
uint32 TransactionId
Definition: c.h:587
size_t Size
Definition: c.h:540
int64 TimestampTz
Definition: timestamp.h:39
int progress
Definition: pgbench.c:274
unsigned int Oid
Definition: postgres_ext.h:31
void SnapshotTooOldMagicForTest(void)
Definition: snapmgr.c:1732
void MaintainOldSnapshotTimeMapping(TimestampTz whenTaken, TransactionId xmin)
Definition: snapmgr.c:1901
bool GlobalVisTestIsRemovableFullXid(GlobalVisState *state, FullTransactionId fxid)
Definition: procarray.c:4181
void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner)
Definition: snapmgr.c:882
bool GlobalVisTestIsRemovableXid(GlobalVisState *state, TransactionId xid)
Definition: procarray.c:4223
bool GlobalVisCheckRemovableFullXid(Relation rel, FullTransactionId fxid)
Definition: procarray.c:4275
TimestampTz GetSnapshotCurrentTimestamp(void)
Definition: snapmgr.c:1678
struct HTAB * HistoricSnapshotGetTupleCids(void)
Definition: snapmgr.c:2107
void AtSubAbort_Snapshot(int level)
Definition: snapmgr.c:987
void SerializeSnapshot(Snapshot snapshot, char *start_address)
Definition: snapmgr.c:2145
void SnapMgrInit(void)
Definition: snapmgr.c:213
void AtEOXact_Snapshot(bool isCommit, bool resetXmin)
Definition: snapmgr.c:1023
bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
Definition: snapmgr.c:2285
static bool OldSnapshotThresholdActive(void)
Definition: snapmgr.h:101
Snapshot GetTransactionSnapshot(void)
Definition: snapmgr.c:250
Snapshot GetLatestSnapshot(void)
Definition: snapmgr.c:325
void TeardownHistoricSnapshot(bool is_error)
Definition: snapmgr.c:2094
Snapshot GetCatalogSnapshot(Oid relid)
Definition: snapmgr.c:386
void UnregisterSnapshot(Snapshot snapshot)
Definition: snapmgr.c:869
void PushActiveSnapshot(Snapshot snapshot)
Definition: snapmgr.c:682
Snapshot RestoreSnapshot(char *start_address)
Definition: snapmgr.c:2204
void AtSubCommit_Snapshot(int level)
Definition: snapmgr.c:966
void UpdateActiveSnapshotCommandId(void)
Definition: snapmgr.c:745
PGDLLIMPORT int old_snapshot_threshold
Definition: snapmgr.c:78
PGDLLIMPORT TransactionId TransactionXmin
Definition: snapmgr.c:112
TransactionId GlobalVisTestNonRemovableHorizon(GlobalVisState *state)
Definition: procarray.c:4261
char * ExportSnapshot(Snapshot snapshot)
Definition: snapmgr.c:1123
bool HistoricSnapshotActive(void)
Definition: snapmgr.c:2101
void ImportSnapshot(const char *idstr)
Definition: snapmgr.c:1394
bool ActiveSnapshotSet(void)
Definition: snapmgr.c:815
PGDLLIMPORT SnapshotData SnapshotAnyData
Definition: snapmgr.c:99
Snapshot RegisterSnapshot(Snapshot snapshot)
Definition: snapmgr.c:827
bool XactHasExportedSnapshots(void)
Definition: snapmgr.c:1569
GlobalVisState * GlobalVisTestFor(Relation rel)
Definition: procarray.c:4066
void DeleteAllExportedSnapshotFiles(void)
Definition: snapmgr.c:1582
PGDLLIMPORT SnapshotData CatalogSnapshotData
Definition: snapmgr.c:97
bool GlobalVisCheckRemovableXid(Relation rel, TransactionId xid)
Definition: procarray.c:4289
bool HaveRegisteredOrActiveSnapshot(void)
Definition: snapmgr.c:1639
void InvalidateCatalogSnapshotConditionally(void)
Definition: snapmgr.c:477
bool ThereAreNoPriorRegisteredSnapshots(void)
Definition: snapmgr.c:1621
void RestoreTransactionSnapshot(Snapshot snapshot, void *source_pgproc)
Definition: snapmgr.c:2269
bool TransactionIdLimitedForOldSnapshots(TransactionId recentXmin, Relation relation, TransactionId *limit_xid, TimestampTz *limit_ts)
Definition: snapmgr.c:1794
void SnapshotSetCommandId(CommandId curcid)
Definition: snapmgr.c:490
void PopActiveSnapshot(void)
Definition: snapmgr.c:776
void PushCopiedSnapshot(Snapshot snapshot)
Definition: snapmgr.c:733
PGDLLIMPORT SnapshotData SnapshotSelfData
Definition: snapmgr.c:98
Size EstimateSnapshotSpace(Snapshot snapshot)
Definition: snapmgr.c:2121
void WaitForOlderSnapshots(TransactionId limitXmin, bool progress)
Definition: indexcmds.c:414
TimestampTz GetOldSnapshotThresholdTimestamp(void)
Definition: snapmgr.c:1703
PGDLLIMPORT bool FirstSnapshotSet
Definition: snapmgr.c:149
Snapshot RegisterSnapshotOnOwner(Snapshot snapshot, ResourceOwner owner)
Definition: snapmgr.c:840
void InvalidateCatalogSnapshot(void)
Definition: snapmgr.c:456
void PushActiveSnapshotWithLevel(Snapshot snapshot, int snap_level)
Definition: snapmgr.c:696
void SetupHistoricSnapshot(Snapshot snapshot_now, struct HTAB *tuplecids)
Definition: snapmgr.c:2078
Snapshot GetNonHistoricCatalogSnapshot(Oid relid)
Definition: snapmgr.c:408
FullTransactionId GlobalVisTestNonRemovableFullHorizon(GlobalVisState *state)
Definition: procarray.c:4250
PGDLLIMPORT TransactionId RecentXmin
Definition: snapmgr.c:113
Size SnapMgrShmemSize(void)
Definition: snapmgr.c:197
Snapshot GetOldestSnapshot(void)
Definition: snapmgr.c:357
void SetOldSnapshotThresholdTimestamp(TimestampTz ts, TransactionId xlimit)
Definition: snapmgr.c:1715
Snapshot GetActiveSnapshot(void)
Definition: snapmgr.c:803
Definition: dynahash.c:220
Definition: regguts.h:318