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/*-------------------------------------------------------------------------
*
* transam.h
* postgres transaction access method support code
*
*
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/transam.h,v 1.67 2009/01/01 17:23:56 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#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)
/* advance a transaction ID variable, handling wraparound correctly */
#define TransactionIdAdvance(dest) \
do { \
(dest)++; \
if ((dest) < FirstNormalTransactionId) \
(dest) = FirstNormalTransactionId; \
} while(0)
/* back up a transaction ID variable, handling wraparound correctly */
#define TransactionIdRetreat(dest) \
do { \
(dest)--; \
} while ((dest) < FirstNormalTransactionId)
/* ----------
* Object ID (OID) zero is InvalidOid.
*
* OIDs 1-9999 are reserved for manual assignment (see the files
* in src/include/catalog/).
*
* OIDS 10000-16383 are reserved for assignment during initdb
* using the OID generator. (We start the generator at 10000.)
*
* 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 10000 and 16384 are completely arbitrary, and can be moved
* if we run low on OIDs in either category. Changing the macros below
* should be sufficient to do this.
*
* 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 FirstBootstrapObjectId 10000
#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 limit_datname 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.
*/
TransactionId 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 */
NameData limit_datname; /* database that needs vacuumed first */
/*
* These fields are protected by ProcArrayLock.
*/
TransactionId latestCompletedXid; /* newest XID that has committed or
* aborted */
} VariableCacheData;
typedef VariableCacheData *VariableCache;
/* ----------------
* extern declarations
* ----------------
*/
/* in transam/varsup.c */
extern 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 TransactionIdAbort(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 TransactionId GetNewTransactionId(bool isSubXact);
extern TransactionId ReadNewTransactionId(void);
extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
Name oldest_datname);
extern Oid GetNewObjectId(void);
#endif /* TRAMSAM_H */
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