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Replace implementation of pg_log as a relation accessed through the

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buffer manager with 'pg_clog', a specialized access method modeled
on pg_xlog.  This simplifies startup (don't need to play games to
open pg_log; among other things, OverrideTransactionSystem goes away),
should improve performance a little, and opens the door to recycling
commit log space by removing no-longer-needed segments of the commit
log.  Actual recycling is not there yet, but I felt I should commit
this part separately since it'd still be useful if we chose not to
do transaction ID wraparound.
This commit is contained in:
Tom Lane
2001-08-25 18:52:43 +00:00
parent 4699d81dc9
commit 2589735da0
39 changed files with 1248 additions and 1128 deletions
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46
src/backend/access/transam/varsup.c
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@@ -6,15 +6,15 @@
* Copyright (c) 2000, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.44 2001/08/23 23:06:37 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.45 2001/08/25 18:52:41 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/clog.h"
#include "access/transam.h"
#include "access/xlog.h"
#include "storage/proc.h"
@@ -32,25 +32,34 @@ VariableCache ShmemVariableCache = NULL;
/*
* Allocate the next XID for my new transaction.
*/
void
GetNewTransactionId(TransactionId *xid)
TransactionId
GetNewTransactionId(void)
{
TransactionId xid;
/*
* During bootstrap initialization, we return the special bootstrap
* transaction id.
*/
if (AMI_OVERRIDE)
{
*xid = BootstrapTransactionId;
return;
}
return BootstrapTransactionId;
SpinAcquire(XidGenLockId);
*xid = ShmemVariableCache->nextXid;
xid = ShmemVariableCache->nextXid;
TransactionIdAdvance(ShmemVariableCache->nextXid);
/*
* If we have just allocated the first XID of a new page of the
* commit log, zero out that commit-log page before returning.
* We must do this while holding XidGenLock, else another xact could
* acquire and commit a later XID before we zero the page. Fortunately,
* a page of the commit log holds 32K or more transactions, so we don't
* have to do this very often.
*/
ExtendCLOG(xid);
/*
* Must set MyProc->xid before releasing XidGenLock. This ensures that
* when GetSnapshotData calls ReadNewTransactionId, all active XIDs
@@ -72,30 +81,33 @@ GetNewTransactionId(TransactionId *xid)
* removed while holding the lock.)
*/
if (MyProc != (PROC *) NULL)
MyProc->xid = *xid;
MyProc->xid = xid;
SpinRelease(XidGenLockId);
return xid;
}
/*
* Read nextXid but don't allocate it.
*/
void
ReadNewTransactionId(TransactionId *xid)
TransactionId
ReadNewTransactionId(void)
{
TransactionId xid;
/*
* During bootstrap initialization, we return the special bootstrap
* transaction id.
*/
if (AMI_OVERRIDE)
{
*xid = BootstrapTransactionId;
return;
}
return BootstrapTransactionId;
SpinAcquire(XidGenLockId);
*xid = ShmemVariableCache->nextXid;
xid = ShmemVariableCache->nextXid;
SpinRelease(XidGenLockId);
return xid;
}
/* ----------------------------------------------------------------