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Rearrange pg_subtrans handling as per recent discussion. pg_subtrans

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updates are no longer WAL-logged nor even fsync'd; we do not need to,
since after a crash no old pg_subtrans data is needed again.  We truncate
pg_subtrans to RecentGlobalXmin at each checkpoint.  slru.c's API is
refactored a little bit to separate out the necessary decisions.
This commit is contained in:
Tom Lane
2004-08-23 23:22:45 +00:00
parent 059912ce2e
commit 4dbb880d3c
13 changed files with 387 additions and 436 deletions
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17
src/backend/storage/ipc/sinval.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.69 2004/08/22 02:41:57 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.70 2004/08/23 23:22:45 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -661,6 +661,9 @@ result_known:
* FALSE is sufficient for non-shared relations, since only backends in my
* own database could ever see the tuples in them.
*
* This is also used to determine where to truncate pg_subtrans. allDbs
* must be TRUE for that case.
*
* Note: we include the currently running xids in the set of considered xids.
* This ensures that if a just-started xact has not yet set its snapshot,
* when it does set the snapshot it cannot set xmin less than what we compute.
@@ -673,7 +676,17 @@ GetOldestXmin(bool allDbs)
TransactionId result;
int index;
result = GetTopTransactionId();
/*
* Normally we start the min() calculation with our own XID. But
* if called by checkpointer, we will not be inside a transaction,
* so use next XID as starting point for min() calculation. (Note
* that if there are no xacts running at all, that will be the subtrans
* truncation point!)
*/
if (IsTransactionState())
result = GetTopTransactionId();
else
result = ReadNewTransactionId();
LWLockAcquire(SInvalLock, LW_SHARED);

13
src/backend/storage/lmgr/lwlock.c
View File

@@ -15,14 +15,13 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.21 2004/07/01 00:50:59 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.22 2004/08/23 23:22:45 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/clog.h"
#include "access/subtrans.h"
#include "access/slru.h"
#include "storage/lwlock.h"
#include "storage/proc.h"
#include "storage/spin.h"
@@ -109,11 +108,11 @@ NumLWLocks(void)
/* bufmgr.c needs two for each shared buffer */
numLocks += 2 * NBuffers;
/* clog.c needs one per CLOG buffer + one control lock */
numLocks += NUM_CLOG_BUFFERS + 1;
/* clog.c needs one per CLOG buffer */
numLocks += NUM_SLRU_BUFFERS;
/* subtrans.c needs one per SubTrans buffer + one control lock */
numLocks += NUM_SUBTRANS_BUFFERS + 1;
/* subtrans.c needs one per SubTrans buffer */
numLocks += NUM_SLRU_BUFFERS;
/* Perhaps create a few more for use by user-defined modules? */