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Diffstat (limited to 'src/include/access/transam.h')
| -rw-r--r-- | src/include/access/transam.h | 370 |
1 files changed, 370 insertions, 0 deletions
diff --git a/src/include/access/transam.h b/src/include/access/transam.h new file mode 100644 index 0000000..2fe8a59 --- /dev/null +++ b/src/include/access/transam.h @@ -0,0 +1,370 @@ +/*------------------------------------------------------------------------- + * + * transam.h + * postgres transaction access method support code + * + * + * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * src/include/access/transam.h + * + *------------------------------------------------------------------------- + */ +#ifndef TRANSAM_H +#define TRANSAM_H + +#include "access/xlogdefs.h" + + +/* ---------------- + * Special transaction ID values + * + * BootstrapTransactionId is the XID for "bootstrap" operations, and + * FrozenTransactionId is used for very old tuples. Both should + * always be considered valid. + * + * FirstNormalTransactionId is the first "normal" transaction id. + * Note: if you need to change it, you must change pg_class.h as well. + * ---------------- + */ +#define InvalidTransactionId ((TransactionId) 0) +#define BootstrapTransactionId ((TransactionId) 1) +#define FrozenTransactionId ((TransactionId) 2) +#define FirstNormalTransactionId ((TransactionId) 3) +#define MaxTransactionId ((TransactionId) 0xFFFFFFFF) + +/* ---------------- + * transaction ID manipulation macros + * ---------------- + */ +#define TransactionIdIsValid(xid) ((xid) != InvalidTransactionId) +#define TransactionIdIsNormal(xid) ((xid) >= FirstNormalTransactionId) +#define TransactionIdEquals(id1, id2) ((id1) == (id2)) +#define TransactionIdStore(xid, dest) (*(dest) = (xid)) +#define StoreInvalidTransactionId(dest) (*(dest) = InvalidTransactionId) + +#define EpochFromFullTransactionId(x) ((uint32) ((x).value >> 32)) +#define XidFromFullTransactionId(x) ((uint32) (x).value) +#define U64FromFullTransactionId(x) ((x).value) +#define FullTransactionIdEquals(a, b) ((a).value == (b).value) +#define FullTransactionIdPrecedes(a, b) ((a).value < (b).value) +#define FullTransactionIdPrecedesOrEquals(a, b) ((a).value <= (b).value) +#define FullTransactionIdFollows(a, b) ((a).value > (b).value) +#define FullTransactionIdFollowsOrEquals(a, b) ((a).value >= (b).value) +#define FullTransactionIdIsValid(x) TransactionIdIsValid(XidFromFullTransactionId(x)) +#define InvalidFullTransactionId FullTransactionIdFromEpochAndXid(0, InvalidTransactionId) +#define FirstNormalFullTransactionId FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId) +#define FullTransactionIdIsNormal(x) FullTransactionIdFollowsOrEquals(x, FirstNormalFullTransactionId) + +/* + * A 64 bit value that contains an epoch and a TransactionId. This is + * wrapped in a struct to prevent implicit conversion to/from TransactionId. + * Not all values represent valid normal XIDs. + */ +typedef struct FullTransactionId +{ + uint64 value; +} FullTransactionId; + +static inline FullTransactionId +FullTransactionIdFromEpochAndXid(uint32 epoch, TransactionId xid) +{ + FullTransactionId result; + + result.value = ((uint64) epoch) << 32 | xid; + + return result; +} + +static inline FullTransactionId +FullTransactionIdFromU64(uint64 value) +{ + FullTransactionId result; + + result.value = value; + + return result; +} + +/* advance a transaction ID variable, handling wraparound correctly */ +#define TransactionIdAdvance(dest) \ + do { \ + (dest)++; \ + if ((dest) < FirstNormalTransactionId) \ + (dest) = FirstNormalTransactionId; \ + } while(0) + +/* + * Retreat a FullTransactionId variable, stepping over xids that would appear + * to be special only when viewed as 32bit XIDs. + */ +static inline void +FullTransactionIdRetreat(FullTransactionId *dest) +{ + dest->value--; + + /* + * In contrast to 32bit XIDs don't step over the "actual" special xids. + * For 64bit xids these can't be reached as part of a wraparound as they + * can in the 32bit case. + */ + if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId)) + return; + + /* + * But we do need to step over XIDs that'd appear special only for 32bit + * XIDs. + */ + while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId) + dest->value--; +} + +/* + * Advance a FullTransactionId variable, stepping over xids that would appear + * to be special only when viewed as 32bit XIDs. + */ +static inline void +FullTransactionIdAdvance(FullTransactionId *dest) +{ + dest->value++; + + /* see FullTransactionIdAdvance() */ + if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId)) + return; + + while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId) + dest->value++; +} + +/* back up a transaction ID variable, handling wraparound correctly */ +#define TransactionIdRetreat(dest) \ + do { \ + (dest)--; \ + } while ((dest) < FirstNormalTransactionId) + +/* compare two XIDs already known to be normal; this is a macro for speed */ +#define NormalTransactionIdPrecedes(id1, id2) \ + (AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \ + (int32) ((id1) - (id2)) < 0) + +/* compare two XIDs already known to be normal; this is a macro for speed */ +#define NormalTransactionIdFollows(id1, id2) \ + (AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \ + (int32) ((id1) - (id2)) > 0) + +/* ---------- + * Object ID (OID) zero is InvalidOid. + * + * OIDs 1-9999 are reserved for manual assignment (see .dat files in + * src/include/catalog/). Of these, 8000-9999 are reserved for + * development purposes (such as in-progress patches and forks); + * they should not appear in released versions. + * + * OIDs 10000-11999 are reserved for assignment by genbki.pl, for use + * when the .dat files in src/include/catalog/ do not specify an OID + * for a catalog entry that requires one. Note that genbki.pl assigns + * these OIDs independently in each catalog, so they're not guaranteed + * to be globally unique. + * + * OIDS 12000-16383 are reserved for assignment during initdb + * using the OID generator. (We start the generator at 12000.) + * + * OIDs beginning at 16384 are assigned from the OID generator + * during normal multiuser operation. (We force the generator up to + * 16384 as soon as we are in normal operation.) + * + * The choices of 8000, 10000 and 12000 are completely arbitrary, and can be + * moved if we run low on OIDs in any category. Changing the macros below, + * and updating relevant documentation (see bki.sgml and RELEASE_CHANGES), + * should be sufficient to do this. Moving the 16384 boundary between + * initdb-assigned OIDs and user-defined objects would be substantially + * more painful, however, since some user-defined OIDs will appear in + * on-disk data; such a change would probably break pg_upgrade. + * + * NOTE: if the OID generator wraps around, we skip over OIDs 0-16383 + * and resume with 16384. This minimizes the odds of OID conflict, by not + * reassigning OIDs that might have been assigned during initdb. + * ---------- + */ +#define FirstGenbkiObjectId 10000 +#define FirstBootstrapObjectId 12000 +#define FirstNormalObjectId 16384 + +/* + * VariableCache is a data structure in shared memory that is used to track + * OID and XID assignment state. For largely historical reasons, there is + * just one struct with different fields that are protected by different + * LWLocks. + * + * Note: xidWrapLimit and oldestXidDB are not "active" values, but are + * used just to generate useful messages when xidWarnLimit or xidStopLimit + * are exceeded. + */ +typedef struct VariableCacheData +{ + /* + * These fields are protected by OidGenLock. + */ + Oid nextOid; /* next OID to assign */ + uint32 oidCount; /* OIDs available before must do XLOG work */ + + /* + * These fields are protected by XidGenLock. + */ + FullTransactionId nextXid; /* next XID to assign */ + + TransactionId oldestXid; /* cluster-wide minimum datfrozenxid */ + TransactionId xidVacLimit; /* start forcing autovacuums here */ + TransactionId xidWarnLimit; /* start complaining here */ + TransactionId xidStopLimit; /* refuse to advance nextXid beyond here */ + TransactionId xidWrapLimit; /* where the world ends */ + Oid oldestXidDB; /* database with minimum datfrozenxid */ + + /* + * These fields are protected by CommitTsLock + */ + TransactionId oldestCommitTsXid; + TransactionId newestCommitTsXid; + + /* + * These fields are protected by ProcArrayLock. + */ + FullTransactionId latestCompletedXid; /* newest full XID that has + * committed or aborted */ + + /* + * Number of top-level transactions with xids (i.e. which may have + * modified the database) that completed in some form since the start of + * the server. This currently is solely used to check whether + * GetSnapshotData() needs to recompute the contents of the snapshot, or + * not. There are likely other users of this. Always above 1. + */ + uint64 xactCompletionCount; + + /* + * These fields are protected by XactTruncationLock + */ + TransactionId oldestClogXid; /* oldest it's safe to look up in clog */ + +} VariableCacheData; + +typedef VariableCacheData *VariableCache; + + +/* ---------------- + * extern declarations + * ---------------- + */ + +/* in transam/xact.c */ +extern bool TransactionStartedDuringRecovery(void); + +/* in transam/varsup.c */ +extern PGDLLIMPORT VariableCache ShmemVariableCache; + +/* + * prototypes for functions in transam/transam.c + */ +extern bool TransactionIdDidCommit(TransactionId transactionId); +extern bool TransactionIdDidAbort(TransactionId transactionId); +extern bool TransactionIdIsKnownCompleted(TransactionId transactionId); +extern void TransactionIdCommitTree(TransactionId xid, int nxids, TransactionId *xids); +extern void TransactionIdAsyncCommitTree(TransactionId xid, int nxids, TransactionId *xids, XLogRecPtr lsn); +extern void TransactionIdAbortTree(TransactionId xid, int nxids, TransactionId *xids); +extern bool TransactionIdPrecedes(TransactionId id1, TransactionId id2); +extern bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2); +extern bool TransactionIdFollows(TransactionId id1, TransactionId id2); +extern bool TransactionIdFollowsOrEquals(TransactionId id1, TransactionId id2); +extern TransactionId TransactionIdLatest(TransactionId mainxid, + int nxids, const TransactionId *xids); +extern XLogRecPtr TransactionIdGetCommitLSN(TransactionId xid); + +/* in transam/varsup.c */ +extern FullTransactionId GetNewTransactionId(bool isSubXact); +extern void AdvanceNextFullTransactionIdPastXid(TransactionId xid); +extern FullTransactionId ReadNextFullTransactionId(void); +extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid, + Oid oldest_datoid); +extern void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid); +extern bool ForceTransactionIdLimitUpdate(void); +extern Oid GetNewObjectId(void); + +#ifdef USE_ASSERT_CHECKING +extern void AssertTransactionIdInAllowableRange(TransactionId xid); +#else +#define AssertTransactionIdInAllowableRange(xid) ((void)true) +#endif + +/* + * Some frontend programs include this header. For compilers that emit static + * inline functions even when they're unused, that leads to unsatisfied + * external references; hence hide them with #ifndef FRONTEND. + */ +#ifndef FRONTEND + +/* + * For callers that just need the XID part of the next transaction ID. + */ +static inline TransactionId +ReadNextTransactionId(void) +{ + return XidFromFullTransactionId(ReadNextFullTransactionId()); +} + +/* return transaction ID backed up by amount, handling wraparound correctly */ +static inline TransactionId +TransactionIdRetreatedBy(TransactionId xid, uint32 amount) +{ + xid -= amount; + + while (xid < FirstNormalTransactionId) + xid--; + + return xid; +} + +/* return the older of the two IDs */ +static inline TransactionId +TransactionIdOlder(TransactionId a, TransactionId b) +{ + if (!TransactionIdIsValid(a)) + return b; + + if (!TransactionIdIsValid(b)) + return a; + + if (TransactionIdPrecedes(a, b)) + return a; + return b; +} + +/* return the older of the two IDs, assuming they're both normal */ +static inline TransactionId +NormalTransactionIdOlder(TransactionId a, TransactionId b) +{ + Assert(TransactionIdIsNormal(a)); + Assert(TransactionIdIsNormal(b)); + if (NormalTransactionIdPrecedes(a, b)) + return a; + return b; +} + +/* return the newer of the two IDs */ +static inline FullTransactionId +FullTransactionIdNewer(FullTransactionId a, FullTransactionId b) +{ + if (!FullTransactionIdIsValid(a)) + return b; + + if (!FullTransactionIdIsValid(b)) + return a; + + if (FullTransactionIdFollows(a, b)) + return a; + return b; +} + +#endif /* FRONTEND */ + +#endif /* TRANSAM_H */ |