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1 : /*-------------------------------------------------------------------------
2 : *
3 : * transam.h
4 : * postgres transaction access method support code
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : * src/include/access/transam.h
11 : *
12 : *-------------------------------------------------------------------------
13 : */
14 : #ifndef TRANSAM_H
15 : #define TRANSAM_H
16 :
17 : #include "access/xlogdefs.h"
18 :
19 :
20 : /* ----------------
21 : * Special transaction ID values
22 : *
23 : * BootstrapTransactionId is the XID for "bootstrap" operations, and
24 : * FrozenTransactionId is used for very old tuples. Both should
25 : * always be considered valid.
26 : *
27 : * FirstNormalTransactionId is the first "normal" transaction id.
28 : * Note: if you need to change it, you must change pg_class.h as well.
29 : * ----------------
30 : */
31 : #define InvalidTransactionId ((TransactionId) 0)
32 : #define BootstrapTransactionId ((TransactionId) 1)
33 : #define FrozenTransactionId ((TransactionId) 2)
34 : #define FirstNormalTransactionId ((TransactionId) 3)
35 : #define MaxTransactionId ((TransactionId) 0xFFFFFFFF)
36 :
37 : /* ----------------
38 : * transaction ID manipulation macros
39 : * ----------------
40 : */
41 : #define TransactionIdIsValid(xid) ((xid) != InvalidTransactionId)
42 : #define TransactionIdIsNormal(xid) ((xid) >= FirstNormalTransactionId)
43 : #define TransactionIdEquals(id1, id2) ((id1) == (id2))
44 : #define TransactionIdStore(xid, dest) (*(dest) = (xid))
45 : #define StoreInvalidTransactionId(dest) (*(dest) = InvalidTransactionId)
46 :
47 : #define EpochFromFullTransactionId(x) ((uint32) ((x).value >> 32))
48 : #define XidFromFullTransactionId(x) ((uint32) (x).value)
49 : #define U64FromFullTransactionId(x) ((x).value)
50 : #define FullTransactionIdPrecedes(a, b) ((a).value < (b).value)
51 : #define FullTransactionIdIsValid(x) TransactionIdIsValid(XidFromFullTransactionId(x))
52 : #define InvalidFullTransactionId FullTransactionIdFromEpochAndXid(0, InvalidTransactionId)
53 :
54 : /*
55 : * A 64 bit value that contains an epoch and a TransactionId. This is
56 : * wrapped in a struct to prevent implicit conversion to/from TransactionId.
57 : * Not all values represent valid normal XIDs.
58 : */
59 : typedef struct FullTransactionId
60 : {
61 : uint64 value;
62 : } FullTransactionId;
63 :
64 : static inline FullTransactionId
65 1392664 : FullTransactionIdFromEpochAndXid(uint32 epoch, TransactionId xid)
66 : {
67 : FullTransactionId result;
68 :
69 1392664 : result.value = ((uint64) epoch) << 32 | xid;
70 :
71 1392664 : return result;
72 : }
73 :
74 : /* advance a transaction ID variable, handling wraparound correctly */
75 : #define TransactionIdAdvance(dest) \
76 : do { \
77 : (dest)++; \
78 : if ((dest) < FirstNormalTransactionId) \
79 : (dest) = FirstNormalTransactionId; \
80 : } while(0)
81 :
82 : /* advance a FullTransactionId variable, stepping over special XIDs */
83 : static inline void
84 255094 : FullTransactionIdAdvance(FullTransactionId *dest)
85 : {
86 255094 : dest->value++;
87 510188 : while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId)
88 0 : dest->value++;
89 255094 : }
90 :
91 : /* back up a transaction ID variable, handling wraparound correctly */
92 : #define TransactionIdRetreat(dest) \
93 : do { \
94 : (dest)--; \
95 : } while ((dest) < FirstNormalTransactionId)
96 :
97 : /* compare two XIDs already known to be normal; this is a macro for speed */
98 : #define NormalTransactionIdPrecedes(id1, id2) \
99 : (AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \
100 : (int32) ((id1) - (id2)) < 0)
101 :
102 : /* compare two XIDs already known to be normal; this is a macro for speed */
103 : #define NormalTransactionIdFollows(id1, id2) \
104 : (AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \
105 : (int32) ((id1) - (id2)) > 0)
106 :
107 : /* ----------
108 : * Object ID (OID) zero is InvalidOid.
109 : *
110 : * OIDs 1-9999 are reserved for manual assignment (see .dat files in
111 : * src/include/catalog/). Of these, 8000-9999 are reserved for
112 : * development purposes (such as in-progress patches and forks);
113 : * they should not appear in released versions.
114 : *
115 : * OIDs 10000-11999 are reserved for assignment by genbki.pl, for use
116 : * when the .dat files in src/include/catalog/ do not specify an OID
117 : * for a catalog entry that requires one.
118 : *
119 : * OIDS 12000-16383 are reserved for assignment during initdb
120 : * using the OID generator. (We start the generator at 12000.)
121 : *
122 : * OIDs beginning at 16384 are assigned from the OID generator
123 : * during normal multiuser operation. (We force the generator up to
124 : * 16384 as soon as we are in normal operation.)
125 : *
126 : * The choices of 8000, 10000 and 12000 are completely arbitrary, and can be
127 : * moved if we run low on OIDs in any category. Changing the macros below,
128 : * and updating relevant documentation (see bki.sgml and RELEASE_CHANGES),
129 : * should be sufficient to do this. Moving the 16384 boundary between
130 : * initdb-assigned OIDs and user-defined objects would be substantially
131 : * more painful, however, since some user-defined OIDs will appear in
132 : * on-disk data; such a change would probably break pg_upgrade.
133 : *
134 : * NOTE: if the OID generator wraps around, we skip over OIDs 0-16383
135 : * and resume with 16384. This minimizes the odds of OID conflict, by not
136 : * reassigning OIDs that might have been assigned during initdb.
137 : * ----------
138 : */
139 : #define FirstGenbkiObjectId 10000
140 : #define FirstBootstrapObjectId 12000
141 : #define FirstNormalObjectId 16384
142 :
143 : /*
144 : * VariableCache is a data structure in shared memory that is used to track
145 : * OID and XID assignment state. For largely historical reasons, there is
146 : * just one struct with different fields that are protected by different
147 : * LWLocks.
148 : *
149 : * Note: xidWrapLimit and oldestXidDB are not "active" values, but are
150 : * used just to generate useful messages when xidWarnLimit or xidStopLimit
151 : * are exceeded.
152 : */
153 : typedef struct VariableCacheData
154 : {
155 : /*
156 : * These fields are protected by OidGenLock.
157 : */
158 : Oid nextOid; /* next OID to assign */
159 : uint32 oidCount; /* OIDs available before must do XLOG work */
160 :
161 : /*
162 : * These fields are protected by XidGenLock.
163 : */
164 : FullTransactionId nextFullXid; /* next full XID to assign */
165 :
166 : TransactionId oldestXid; /* cluster-wide minimum datfrozenxid */
167 : TransactionId xidVacLimit; /* start forcing autovacuums here */
168 : TransactionId xidWarnLimit; /* start complaining here */
169 : TransactionId xidStopLimit; /* refuse to advance nextFullXid beyond here */
170 : TransactionId xidWrapLimit; /* where the world ends */
171 : Oid oldestXidDB; /* database with minimum datfrozenxid */
172 :
173 : /*
174 : * These fields are protected by CommitTsLock
175 : */
176 : TransactionId oldestCommitTsXid;
177 : TransactionId newestCommitTsXid;
178 :
179 : /*
180 : * These fields are protected by ProcArrayLock.
181 : */
182 : TransactionId latestCompletedXid; /* newest XID that has committed or
183 : * aborted */
184 :
185 : /*
186 : * These fields are protected by CLogTruncationLock
187 : */
188 : TransactionId oldestClogXid; /* oldest it's safe to look up in clog */
189 :
190 : } VariableCacheData;
191 :
192 : typedef VariableCacheData *VariableCache;
193 :
194 :
195 : /* ----------------
196 : * extern declarations
197 : * ----------------
198 : */
199 :
200 : /* in transam/xact.c */
201 : extern bool TransactionStartedDuringRecovery(void);
202 :
203 : /* in transam/varsup.c */
204 : extern PGDLLIMPORT VariableCache ShmemVariableCache;
205 :
206 : /*
207 : * prototypes for functions in transam/transam.c
208 : */
209 : extern bool TransactionIdDidCommit(TransactionId transactionId);
210 : extern bool TransactionIdDidAbort(TransactionId transactionId);
211 : extern bool TransactionIdIsKnownCompleted(TransactionId transactionId);
212 : extern void TransactionIdCommitTree(TransactionId xid, int nxids, TransactionId *xids);
213 : extern void TransactionIdAsyncCommitTree(TransactionId xid, int nxids, TransactionId *xids, XLogRecPtr lsn);
214 : extern void TransactionIdAbortTree(TransactionId xid, int nxids, TransactionId *xids);
215 : extern bool TransactionIdPrecedes(TransactionId id1, TransactionId id2);
216 : extern bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2);
217 : extern bool TransactionIdFollows(TransactionId id1, TransactionId id2);
218 : extern bool TransactionIdFollowsOrEquals(TransactionId id1, TransactionId id2);
219 : extern TransactionId TransactionIdLatest(TransactionId mainxid,
220 : int nxids, const TransactionId *xids);
221 : extern XLogRecPtr TransactionIdGetCommitLSN(TransactionId xid);
222 :
223 : /* in transam/varsup.c */
224 : extern FullTransactionId GetNewTransactionId(bool isSubXact);
225 : extern void AdvanceNextFullTransactionIdPastXid(TransactionId xid);
226 : extern FullTransactionId ReadNextFullTransactionId(void);
227 : extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
228 : Oid oldest_datoid);
229 : extern void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid);
230 : extern bool ForceTransactionIdLimitUpdate(void);
231 : extern Oid GetNewObjectId(void);
232 :
233 : /*
234 : * Some frontend programs include this header. For compilers that emit static
235 : * inline functions even when they're unused, that leads to unsatisfied
236 : * external references; hence hide them with #ifndef FRONTEND.
237 : */
238 : #ifndef FRONTEND
239 :
240 : /*
241 : * For callers that just need the XID part of the next transaction ID.
242 : */
243 : static inline TransactionId
244 97342 : ReadNewTransactionId(void)
245 : {
246 97342 : return XidFromFullTransactionId(ReadNextFullTransactionId());
247 : }
248 :
249 : #endif /* FRONTEND */
250 :
251 : #endif /* TRANSAM_H */
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