hide it behind #ifdef WAL_DEBUG blocks.
.
.
.
- wal_debug | 0
+ wal_debug | off
wal_sync_method | fdatasync
(94 rows)
- wal_debug (integer)
+ wal_debug (boolean)
- If nonzero, turn on WAL-related debugging output.
+ If true, emit WAL-related debugging output. This option is
+ only available if the WAL_DEBUG macro was
+ defined when
PostgreSQL was
+ compiled.
-
+
Write-Ahead Logging (<acronym>WAL</acronym>)
transaction processing. Briefly,
WAL's central
concept is that changes to data files (where tables and indexes
reside) must be written only after those changes have been logged,
- that is, when log records have been flushed to permanent
- storage. If we follow this procedure, we do not need to flush
- data pages to disk on every transaction commit, because we know
- that in the event of a crash we will be able to recover the
+ that is, when log records describing the changes have been flushed
+ to permanent storage. If we follow this procedure, we do not need
+ to flush data pages to disk on every transaction commit, because we
+ know that in the event of a crash we will be able to recover the
database using the log: any changes that have not been applied to
the data pages will first be redone from the log records (this is
roll-forward recovery, also known as REDO) and then changes made by
There will be at least one 16 MB segment file, and will normally
not be more than 2 * checkpoint_segments + 1
- files. You can use this to estimate space requirements for WAL.
+ files. You can use this to estimate space requirements for
WAL.
Ordinarily, when old log segment files are no longer needed, they
are recycled (renamed to become the next segments in the numbered
sequence). If, due to a short-term peak of log output rate, there
The wal_sync_method parameter determines how
PostgreSQL will ask the kernel to force
- WAL updates out to disk.
+
WAL updates out to disk.
All the options should be the same as far as reliability goes,
but it's quite platform-specific which one will be the fastest.
Note that this parameter is irrelevant if fsync
- Setting the wal_debug parameter to any nonzero
- value will result in each LogInsert and
+ Enabling the wal_debug configuration parameter
+ will result in each LogInsert and
- logged to the server log. At present, it makes no difference what
- the nonzero value is. This option may be replaced by a more
+ logged to the server log. This option may be replaced by a more
general mechanism in the future.
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.129 2003/12/20 17:31:20 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.130 2004/01/06 17:26:23 neilc Exp $
*
*-------------------------------------------------------------------------
*/
/* User-settable parameters */
int CheckPointSegments = 3;
int XLOGbuffers = 8;
-int XLOG_DEBUG = 0;
char *XLOG_sync_method = NULL;
const char XLOG_sync_method_default[] = DEFAULT_SYNC_METHOD_STR;
char XLOG_archive_dir[MAXPGPATH]; /* null string means
* delete 'em */
+#ifdef WAL_DEBUG
+bool XLOG_DEBUG = false;
+#endif
+
/*
* XLOGfileslop is used in the code as the allowed "fuzz" in the number of
* preallocated XLOG segments --- we try to have at least XLOGfiles advance
MyProc->logRec = RecPtr;
}
+#ifdef WAL_DEBUG
if (XLOG_DEBUG)
{
char buf[8192];
}
elog(LOG, "%s", buf);
}
+#endif
/* Record begin of record in appropriate places */
if (!no_tran)
openLogSeg >= (RedoRecPtr.xrecoff / XLogSegSize) +
(uint32) CheckPointSegments))
{
+#ifdef WAL_DEBUG
if (XLOG_DEBUG)
elog(LOG, "time for a checkpoint, signaling postmaster");
+#endif
SendPostmasterSignal(PMSIGNAL_DO_CHECKPOINT);
}
}
if (XLByteLE(record, LogwrtResult.Flush))
return;
+#ifdef WAL_DEBUG
if (XLOG_DEBUG)
elog(LOG, "xlog flush request %X/%X; write %X/%X; flush %X/%X",
record.xlogid, record.xrecoff,
LogwrtResult.Write.xlogid, LogwrtResult.Write.xrecoff,
LogwrtResult.Flush.xlogid, LogwrtResult.Flush.xrecoff);
+#endif
START_CRIT_SECTION();
/* This is just to allow attaching to startup process with a debugger */
#ifdef XLOG_REPLAY_DELAY
+#ifdef WAL_DEBUG
if (XLOG_DEBUG && ControlFile->state != DB_SHUTDOWNED)
sleep(60);
+#endif
#endif
/*
ShmemVariableCache->nextXid = record->xl_xid;
TransactionIdAdvance(ShmemVariableCache->nextXid);
}
+
+#ifdef WAL_DEBUG
if (XLOG_DEBUG)
{
char buf[8192];
record->xl_info, XLogRecGetData(record));
elog(LOG, "%s", buf);
}
+#endif
if (record->xl_info & XLR_BKP_BLOCK_MASK)
RestoreBkpBlocks(record, EndRecPtr);
* Written by Peter Eisentraut
. *
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.175 2003/12/03 18:52:00 joe Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.176 2004/01/06 17:26:23 neilc Exp $
*
*--------------------------------------------------------------------
*/
* TO ADD AN OPTION:
*
* 1. Declare a global variable of type bool, int, double, or char*
- * and make use of it.
+ * and make use of it.
*
* 2. Decide at what times it's safe to set the option. See guc.h for
- * details.
+ * details.
*
* 3. Decide on a name, a default value, upper and lower bounds (if
- * applicable), etc.
+ * applicable), etc.
*
* 4. Add a record below.
*
- * 5. Add it to src/backend/utils/misc/postgresql.conf.sample.
+ * 5. Add it to src/backend/utils/misc/postgresql.conf.sample, if
+ * appropriate
*
* 6. Add it to src/bin/psql/tab-complete.c, if it's a USERSET option.
*
#endif
},
+#ifdef WAL_DEBUG
+ {
+ {"wal_debug", PGC_SUSET, DEVELOPER_OPTIONS,
+ gettext_noop("Emit WAL-related debugging output."),
+ NULL,
+ GUC_NOT_IN_SAMPLE
+ },
+ &XLOG_DEBUG,
+ false, NULL, NULL
+ },
+#endif
+
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL
8, 4, INT_MAX, NULL, NULL
},
- {
- {"wal_debug", PGC_SUSET, DEVELOPER_OPTIONS,
- gettext_noop("If nonzero, WAL-related debugging output is logged."),
- NULL,
- GUC_NOT_IN_SAMPLE
- },
- &XLOG_DEBUG,
- 0, 0, 16, NULL, NULL
- },
-
{
{"commit_delay", PGC_USERSET, WAL_CHECKPOINTS,
gettext_noop("Sets the delay in microseconds between transaction commit and "
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.46 2003/12/12 18:45:10 petere Exp $
+ * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.47 2004/01/06 17:26:23 neilc Exp $
*/
#ifndef XLOG_H
#define XLOG_H
extern int CheckPointSegments;
extern int CheckPointWarning;
extern int XLOGbuffers;
-extern int XLOG_DEBUG;
extern char *XLOG_sync_method;
extern const char XLOG_sync_method_default[];
+#ifdef WAL_DEBUG
+extern bool XLOG_DEBUG;
+#endif
extern XLogRecPtr XLogInsert(RmgrId rmid, uint8 info, XLogRecData *rdata);
extern void XLogFlush(XLogRecPtr RecPtr);
* for developers. If you edit any of these, be sure to do a *full*
* rebuild (and an initdb if noted).
*
- * $PostgreSQL: pgsql/src/include/pg_config_manual.h,v 1.8 2003/11/29 22:40:53 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/pg_config_manual.h,v 1.9 2004/01/06 17:26:23 neilc Exp $
*------------------------------------------------------------------------
*/
*/
/* #define LOCK_DEBUG */
+/*
+ * Enable debugging print statements for WAL-related operations; see
+ * also the wal_debug GUC var.
+ */
+/* #define WAL_DEBUG */
+
/*
* Other debug #defines (documentation, anyone?)
*/
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