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/*-------------------------------------------------------------------------
*
* transam.c
* postgres transaction log interface routines
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/transam/transam.c,v 1.47 2001/08/25 18:52:41 tgl Exp $
*
* NOTES
* This file contains the high level access-method interface to the
* transaction system.
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/clog.h"
#include "access/transam.h"
static bool TransactionLogTest(TransactionId transactionId, XidStatus status);
static void TransactionLogUpdate(TransactionId transactionId,
XidStatus status);
/* ----------------
* Single-item cache for results of TransactionLogTest.
* ----------------
*/
static TransactionId cachedTestXid = InvalidTransactionId;
static XidStatus cachedTestXidStatus;
/* ----------------------------------------------------------------
* postgres log access method interface
*
* TransactionLogTest
* TransactionLogUpdate
* ----------------------------------------------------------------
*/
/* --------------------------------
* TransactionLogTest
* --------------------------------
*/
static bool /* true/false: does transaction id have
* specified status? */
TransactionLogTest(TransactionId transactionId, /* transaction id to test */
XidStatus status) /* transaction status */
{
XidStatus xidstatus; /* recorded status of xid */
/*
* Before going to the commit log manager, check our single item cache to
* see if we didn't just check the transaction status a moment ago.
*/
if (TransactionIdEquals(transactionId, cachedTestXid))
return (status == cachedTestXidStatus);
/*
* Also, check to see if the transaction ID is a permanent one.
*/
if (! TransactionIdIsNormal(transactionId))
{
if (TransactionIdEquals(transactionId, BootstrapTransactionId))
return (status == TRANSACTION_STATUS_COMMITTED);
if (TransactionIdEquals(transactionId, FrozenTransactionId))
return (status == TRANSACTION_STATUS_COMMITTED);
return (status == TRANSACTION_STATUS_ABORTED);
}
/*
* Get the status.
*/
xidstatus = TransactionIdGetStatus(transactionId);
/*
* DO NOT cache status for unfinished transactions!
*/
if (xidstatus != TRANSACTION_STATUS_IN_PROGRESS)
{
TransactionIdStore(transactionId, &cachedTestXid);
cachedTestXidStatus = xidstatus;
}
return (status == xidstatus);
}
/* --------------------------------
* TransactionLogUpdate
* --------------------------------
*/
static void
TransactionLogUpdate(TransactionId transactionId, /* trans id to update */
XidStatus status) /* new trans status */
{
/*
* update the commit log
*/
TransactionIdSetStatus(transactionId, status);
/*
* update (invalidate) our single item TransactionLogTest cache.
*/
TransactionIdStore(transactionId, &cachedTestXid);
cachedTestXidStatus = status;
}
/* --------------------------------
* AmiTransactionOverride
*
* This function is used to manipulate the bootstrap flag.
* --------------------------------
*/
void
AmiTransactionOverride(bool flag)
{
AMI_OVERRIDE = flag;
}
/* ----------------------------------------------------------------
* Interface functions
*
* TransactionId DidCommit
* TransactionId DidAbort
* TransactionId IsInProgress
* ========
* these functions test the transaction status of
* a specified transaction id.
*
* TransactionId Commit
* TransactionId Abort
* ========
* these functions set the transaction status
* of the specified xid.
*
* ----------------------------------------------------------------
*/
/* --------------------------------
* TransactionId DidCommit
* TransactionId DidAbort
* TransactionId IsInProgress
* --------------------------------
*/
/*
* TransactionIdDidCommit
* True iff transaction associated with the identifier did commit.
*
* Note:
* Assumes transaction identifier is valid.
*/
bool /* true if given transaction committed */
TransactionIdDidCommit(TransactionId transactionId)
{
if (AMI_OVERRIDE)
return true;
return TransactionLogTest(transactionId, TRANSACTION_STATUS_COMMITTED);
}
/*
* TransactionIdDidAbort
* True iff transaction associated with the identifier did abort.
*
* Note:
* Assumes transaction identifier is valid.
*/
bool /* true if given transaction aborted */
TransactionIdDidAbort(TransactionId transactionId)
{
if (AMI_OVERRIDE)
return false;
return TransactionLogTest(transactionId, TRANSACTION_STATUS_ABORTED);
}
/*
* Now this func in shmem.c and gives quality answer by scanning
* PROC structures of all running backend. - vadim 11/26/96
*
* Old comments:
* true if given transaction has neither committed nor aborted
*/
#ifdef NOT_USED
bool
TransactionIdIsInProgress(TransactionId transactionId)
{
if (AMI_OVERRIDE)
return false;
return TransactionLogTest(transactionId, TRANSACTION_STATUS_IN_PROGRESS);
}
#endif /* NOT_USED */
/* --------------------------------
* TransactionId Commit
* TransactionId Abort
* --------------------------------
*/
/*
* TransactionIdCommit
* Commits the transaction associated with the identifier.
*
* Note:
* Assumes transaction identifier is valid.
*/
void
TransactionIdCommit(TransactionId transactionId)
{
if (AMI_OVERRIDE)
return;
TransactionLogUpdate(transactionId, TRANSACTION_STATUS_COMMITTED);
}
/*
* TransactionIdAbort
* Aborts the transaction associated with the identifier.
*
* Note:
* Assumes transaction identifier is valid.
*/
void
TransactionIdAbort(TransactionId transactionId)
{
if (AMI_OVERRIDE)
return;
TransactionLogUpdate(transactionId, TRANSACTION_STATUS_ABORTED);
}
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