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Fix recently-understood problems with handling of XID freezing, particularly

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in PITR scenarios.  We now WAL-log the replacement of old XIDs with
FrozenTransactionId, so that such replacement is guaranteed to propagate to
PITR slave databases.  Also, rather than relying on hint-bit updates to be
preserved, pg_clog is not truncated until all instances of an XID are known to
have been replaced by FrozenTransactionId.  Add new GUC variables and
pg_autovacuum columns to allow management of the freezing policy, so that
users can trade off the size of pg_clog against the amount of freezing work
done.  Revise the already-existing code that forces autovacuum of tables
approaching the wraparound point to make it more bulletproof; also, revise the
autovacuum logic so that anti-wraparound vacuuming is done per-table rather
than per-database.  initdb forced because of changes in pg_class, pg_database,
and pg_autovacuum catalogs.  Heikki Linnakangas, Simon Riggs, and Tom Lane.
This commit is contained in:
Tom Lane
2006-11-05 22:42:10 +00:00
parent 10c70b8602
commit 48188e1621
43 changed files with 1284 additions and 1062 deletions
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74
src/backend/access/transam/clog.c
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@ -24,7 +24,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.40 2006/10/04 00:29:49 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.41 2006/11/05 22:42:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -69,6 +69,7 @@ static SlruCtlData ClogCtlData;
static int ZeroCLOGPage(int pageno, bool writeXlog);
static bool CLOGPagePrecedes(int page1, int page2);
static void WriteZeroPageXlogRec(int pageno);
static void WriteTruncateXlogRec(int pageno);
/*
@ -309,16 +310,17 @@ ExtendCLOG(TransactionId newestXact)
/*
* Remove all CLOG segments before the one holding the passed transaction ID
*
* When this is called, we know that the database logically contains no
* reference to transaction IDs older than oldestXact. However, we must
* not truncate the CLOG until we have performed a checkpoint, to ensure
* that no such references remain on disk either; else a crash just after
* the truncation might leave us with a problem. Since CLOG segments hold
* a large number of transactions, the opportunity to actually remove a
* segment is fairly rare, and so it seems best not to do the checkpoint
* unless we have confirmed that there is a removable segment. Therefore
* we issue the checkpoint command here, not in higher-level code as might
* seem cleaner.
* Before removing any CLOG data, we must flush XLOG to disk, to ensure
* that any recently-emitted HEAP_FREEZE records have reached disk; otherwise
* a crash and restart might leave us with some unfrozen tuples referencing
* removed CLOG data. We choose to emit a special TRUNCATE XLOG record too.
* Replaying the deletion from XLOG is not critical, since the files could
* just as well be removed later, but doing so prevents a long-running hot
* standby server from acquiring an unreasonably bloated CLOG directory.
*
* Since CLOG segments hold a large number of transactions, the opportunity to
* actually remove a segment is fairly rare, and so it seems best not to do
* the XLOG flush unless we have confirmed that there is a removable segment.
*/
void
TruncateCLOG(TransactionId oldestXact)
@ -335,8 +337,8 @@ TruncateCLOG(TransactionId oldestXact)
if (!SlruScanDirectory(ClogCtl, cutoffPage, false))
return; /* nothing to remove */
/* Perform a CHECKPOINT */
RequestCheckpoint(true, false);
/* Write XLOG record and flush XLOG to disk */
WriteTruncateXlogRec(cutoffPage);
/* Now we can remove the old CLOG segment(s) */
SimpleLruTruncate(ClogCtl, cutoffPage);
@ -386,6 +388,29 @@ WriteZeroPageXlogRec(int pageno)
(void) XLogInsert(RM_CLOG_ID, CLOG_ZEROPAGE | XLOG_NO_TRAN, &rdata);
}
/*
* Write a TRUNCATE xlog record
*
* We must flush the xlog record to disk before returning --- see notes
* in TruncateCLOG().
*
* Note: xlog record is marked as outside transaction control, since we
* want it to be redone whether the invoking transaction commits or not.
*/
static void
WriteTruncateXlogRec(int pageno)
{
XLogRecData rdata;
XLogRecPtr recptr;
rdata.data = (char *) (&pageno);
rdata.len = sizeof(int);
rdata.buffer = InvalidBuffer;
rdata.next = NULL;
recptr = XLogInsert(RM_CLOG_ID, CLOG_TRUNCATE | XLOG_NO_TRAN, &rdata);
XLogFlush(recptr);
}
/*
* CLOG resource manager's routines
*/
@ -409,6 +434,22 @@ clog_redo(XLogRecPtr lsn, XLogRecord *record)
LWLockRelease(CLogControlLock);
}
else if (info == CLOG_TRUNCATE)
{
int pageno;
memcpy(&pageno, XLogRecGetData(record), sizeof(int));
/*
* During XLOG replay, latest_page_number isn't set up yet; insert
* a suitable value to bypass the sanity test in SimpleLruTruncate.
*/
ClogCtl->shared->latest_page_number = pageno;
SimpleLruTruncate(ClogCtl, pageno);
}
else
elog(PANIC, "clog_redo: unknown op code %u", info);
}
void
@ -423,6 +464,13 @@ clog_desc(StringInfo buf, uint8 xl_info, char *rec)
memcpy(&pageno, rec, sizeof(int));
appendStringInfo(buf, "zeropage: %d", pageno);
}
else if (info == CLOG_TRUNCATE)
{
int pageno;
memcpy(&pageno, rec, sizeof(int));
appendStringInfo(buf, "truncate before: %d", pageno);
}
else
appendStringInfo(buf, "UNKNOWN");
}