ea42cc18c3
This provides infrastructure for looking up arbitrary, user-supplied XIDs without a risk of scary-looking failures from within the clog module. Normally, the oldest XID that can be safely looked up in CLOG is the same as the oldest XID that can reused without causing wraparound, and the latter is already tracked. However, while truncation is in progress, the values are different, so we must keep track of them separately. Craig Ringer, reviewed by Simon Riggs and by me. Discussion: http://postgr.es/m/CAMsr+YHQiWNEi0daCTboS40T+V5s_+dst3PYv_8v2wNVH+Xx4g@mail.gmail.com
187 lines
6.5 KiB
C
187 lines
6.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* transam.h
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* postgres transaction access method support code
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*
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*
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* Portions Copyright (c) 1996-2017, 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/access/transam.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef TRANSAM_H
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#define TRANSAM_H
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#include "access/xlogdefs.h"
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/* ----------------
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* Special transaction ID values
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*
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* BootstrapTransactionId is the XID for "bootstrap" operations, and
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* FrozenTransactionId is used for very old tuples. Both should
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* always be considered valid.
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*
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* FirstNormalTransactionId is the first "normal" transaction id.
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* Note: if you need to change it, you must change pg_class.h as well.
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* ----------------
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*/
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#define InvalidTransactionId ((TransactionId) 0)
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#define BootstrapTransactionId ((TransactionId) 1)
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#define FrozenTransactionId ((TransactionId) 2)
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#define FirstNormalTransactionId ((TransactionId) 3)
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#define MaxTransactionId ((TransactionId) 0xFFFFFFFF)
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/* ----------------
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* transaction ID manipulation macros
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* ----------------
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*/
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#define TransactionIdIsValid(xid) ((xid) != InvalidTransactionId)
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#define TransactionIdIsNormal(xid) ((xid) >= FirstNormalTransactionId)
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#define TransactionIdEquals(id1, id2) ((id1) == (id2))
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#define TransactionIdStore(xid, dest) (*(dest) = (xid))
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#define StoreInvalidTransactionId(dest) (*(dest) = InvalidTransactionId)
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/* advance a transaction ID variable, handling wraparound correctly */
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#define TransactionIdAdvance(dest) \
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do { \
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(dest)++; \
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if ((dest) < FirstNormalTransactionId) \
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(dest) = FirstNormalTransactionId; \
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} while(0)
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/* back up a transaction ID variable, handling wraparound correctly */
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#define TransactionIdRetreat(dest) \
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do { \
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(dest)--; \
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} while ((dest) < FirstNormalTransactionId)
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/* compare two XIDs already known to be normal; this is a macro for speed */
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#define NormalTransactionIdPrecedes(id1, id2) \
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(AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \
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(int32) ((id1) - (id2)) < 0)
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/* compare two XIDs already known to be normal; this is a macro for speed */
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#define NormalTransactionIdFollows(id1, id2) \
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(AssertMacro(TransactionIdIsNormal(id1) && TransactionIdIsNormal(id2)), \
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(int32) ((id1) - (id2)) > 0)
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/* ----------
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* Object ID (OID) zero is InvalidOid.
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*
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* OIDs 1-9999 are reserved for manual assignment (see the files
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* in src/include/catalog/).
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*
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* OIDS 10000-16383 are reserved for assignment during initdb
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* using the OID generator. (We start the generator at 10000.)
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*
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* OIDs beginning at 16384 are assigned from the OID generator
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* during normal multiuser operation. (We force the generator up to
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* 16384 as soon as we are in normal operation.)
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*
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* The choices of 10000 and 16384 are completely arbitrary, and can be moved
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* if we run low on OIDs in either category. Changing the macros below
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* should be sufficient to do this.
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*
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* NOTE: if the OID generator wraps around, we skip over OIDs 0-16383
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* and resume with 16384. This minimizes the odds of OID conflict, by not
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* reassigning OIDs that might have been assigned during initdb.
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* ----------
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*/
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#define FirstBootstrapObjectId 10000
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#define FirstNormalObjectId 16384
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/*
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* VariableCache is a data structure in shared memory that is used to track
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* OID and XID assignment state. For largely historical reasons, there is
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* just one struct with different fields that are protected by different
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* LWLocks.
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*
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* Note: xidWrapLimit and oldestXidDB are not "active" values, but are
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* used just to generate useful messages when xidWarnLimit or xidStopLimit
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* are exceeded.
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*/
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typedef struct VariableCacheData
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{
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/*
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* These fields are protected by OidGenLock.
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*/
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Oid nextOid; /* next OID to assign */
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uint32 oidCount; /* OIDs available before must do XLOG work */
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/*
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* These fields are protected by XidGenLock.
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*/
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TransactionId nextXid; /* next XID to assign */
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TransactionId oldestXid; /* cluster-wide minimum datfrozenxid */
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TransactionId xidVacLimit; /* start forcing autovacuums here */
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TransactionId xidWarnLimit; /* start complaining here */
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TransactionId xidStopLimit; /* refuse to advance nextXid beyond here */
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TransactionId xidWrapLimit; /* where the world ends */
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Oid oldestXidDB; /* database with minimum datfrozenxid */
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/*
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* These fields are protected by CommitTsLock
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*/
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TransactionId oldestCommitTsXid;
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TransactionId newestCommitTsXid;
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/*
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* These fields are protected by ProcArrayLock.
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*/
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TransactionId latestCompletedXid; /* newest XID that has committed or
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* aborted */
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/*
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* These fields are protected by CLogTruncationLock
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*/
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TransactionId oldestClogXid; /* oldest it's safe to look up in clog */
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} VariableCacheData;
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typedef VariableCacheData *VariableCache;
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/* ----------------
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* extern declarations
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* ----------------
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*/
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/* in transam/xact.c */
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extern bool TransactionStartedDuringRecovery(void);
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/* in transam/varsup.c */
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extern PGDLLIMPORT VariableCache ShmemVariableCache;
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/*
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* prototypes for functions in transam/transam.c
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*/
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extern bool TransactionIdDidCommit(TransactionId transactionId);
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extern bool TransactionIdDidAbort(TransactionId transactionId);
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extern bool TransactionIdIsKnownCompleted(TransactionId transactionId);
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extern void TransactionIdAbort(TransactionId transactionId);
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extern void TransactionIdCommitTree(TransactionId xid, int nxids, TransactionId *xids);
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extern void TransactionIdAsyncCommitTree(TransactionId xid, int nxids, TransactionId *xids, XLogRecPtr lsn);
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extern void TransactionIdAbortTree(TransactionId xid, int nxids, TransactionId *xids);
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extern bool TransactionIdPrecedes(TransactionId id1, TransactionId id2);
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extern bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2);
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extern bool TransactionIdFollows(TransactionId id1, TransactionId id2);
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extern bool TransactionIdFollowsOrEquals(TransactionId id1, TransactionId id2);
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extern TransactionId TransactionIdLatest(TransactionId mainxid,
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int nxids, const TransactionId *xids);
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extern XLogRecPtr TransactionIdGetCommitLSN(TransactionId xid);
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/* in transam/varsup.c */
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extern TransactionId GetNewTransactionId(bool isSubXact);
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extern TransactionId ReadNewTransactionId(void);
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extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
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Oid oldest_datoid);
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extern void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid);
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extern bool ForceTransactionIdLimitUpdate(void);
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extern Oid GetNewObjectId(void);
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#endif /* TRAMSAM_H */
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