Introduce wal_level GUC to explicitly control if information needed for

archival or hot standby should be WAL-logged, instead of deducing that from
other options like archive_mode. This replaces recovery_connections GUC in
the primary, where it now has no effect, but it's still used in the standby
to enable/disable hot standby.

Remove the WAL-logging of "unlogged operations", like creating an index
without WAL-logging and fsyncing it at the end. Instead, we keep a copy of
the wal_mode setting and the settings that affect how much shared memory a
hot standby server needs to track master transactions (max_connections,
max_prepared_xacts, max_locks_per_xact) in pg_control. Whenever the settings
change, at server restart, write a WAL record noting the new settings and
update pg_control. This allows us to notice the change in those settings in
the standby at the right moment, they used to be included in checkpoint
records, but that meant that a changed value was not reflected in the
standby until the first checkpoint after the change.

Bump PG_CONTROL_VERSION and XLOG_PAGE_MAGIC. Whack XLOG_PAGE_MAGIC back to
the sequence it used to follow, before hot standby and subsequent patches
changed it to 0x9003.

4 files changed, 30 insertions, 25 deletions

diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 4812997659..6936a2a579 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.109 2010/04/20 11:15:06 rhaas Exp $
+ * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.110 2010/04/28 16:10:43 heikki Exp $
  */
 #ifndef XLOG_H
 #define XLOG_H
@@ -195,24 +195,26 @@ extern int	XLogArchiveTimeout;
 extern bool log_checkpoints;
 extern bool XLogRequestRecoveryConnections;
 extern int	MaxStandbyDelay;
+/* WAL levels */
+typedef enum WalLevel
+{
+	WAL_LEVEL_MINIMAL = 0,
+	WAL_LEVEL_ARCHIVE,
+	WAL_LEVEL_HOT_STANDBY
+} WalLevel;
+extern int	wal_level;
 
-#define XLogArchivingActive()	(XLogArchiveMode)
+#define XLogArchivingActive()	(XLogArchiveMode && wal_level >= WAL_LEVEL_ARCHIVE)
 #define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0')
 
 /*
- * This is in walsender.c, but declared here so that we don't need to include
- * walsender.h in all files that check XLogIsNeeded()
- */
-extern int	max_wal_senders;
-
-/*
- * Is WAL-logging necessary? We need to log an XLOG record iff either
- * WAL archiving is enabled or XLOG streaming is allowed.
+ * Is WAL-logging necessary for archival or log-shipping, or can we skip
+ * WAL-logging if we fsync() the data before committing instead?
  */
-#define XLogIsNeeded() (XLogArchivingActive() || (max_wal_senders > 0))
+#define XLogIsNeeded() (wal_level >= WAL_LEVEL_ARCHIVE)
 
 /* Do we need to WAL-log information required only for Hot Standby? */
-#define XLogStandbyInfoActive() (XLogRequestRecoveryConnections && XLogIsNeeded())
+#define XLogStandbyInfoActive() (wal_level >= WAL_LEVEL_HOT_STANDBY)
 
 #ifdef WAL_DEBUG
 extern bool XLOG_DEBUG;
@@ -293,7 +295,6 @@ extern void InitXLOGAccess(void);
 extern void CreateCheckPoint(int flags);
 extern bool CreateRestartPoint(int flags);
 extern void XLogPutNextOid(Oid nextOid);
-extern void XLogReportUnloggedStatement(char *reason);
 extern XLogRecPtr GetRedoRecPtr(void);
 extern XLogRecPtr GetInsertRecPtr(void);
 extern XLogRecPtr GetWriteRecPtr(void);
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index fa21f0a916..3f0930f395 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/xlog_internal.h,v 1.32 2010/04/12 10:40:43 heikki Exp $
+ * $PostgreSQL: pgsql/src/include/access/xlog_internal.h,v 1.33 2010/04/28 16:10:43 heikki Exp $
  */
 #ifndef XLOG_INTERNAL_H
 #define XLOG_INTERNAL_H
@@ -71,7 +71,7 @@ typedef struct XLogContRecord
 /*
  * Each page of XLOG file has a header like this:
  */
-#define XLOG_PAGE_MAGIC 0x9003	/* can be used as WAL version indicator */
+#define XLOG_PAGE_MAGIC 0xD064	/* can be used as WAL version indicator */
 
 typedef struct XLogPageHeaderData
 {
diff --git a/src/include/catalog/pg_control.h b/src/include/catalog/pg_control.h
index 7342468d05..8deef6d354 100644
--- a/src/include/catalog/pg_control.h
+++ b/src/include/catalog/pg_control.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_control.h,v 1.53 2010/04/23 20:21:31 sriggs Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_control.h,v 1.54 2010/04/28 16:10:43 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,7 +21,7 @@
 
 
 /* Version identifier for this pg_control format */
-#define PG_CONTROL_VERSION	901
+#define PG_CONTROL_VERSION	902
 
 /*
  * Body of CheckPoint XLOG records.  This is declared here because we keep
@@ -41,12 +41,6 @@ typedef struct CheckPoint
 	Oid			oldestXidDB;	/* database with minimum datfrozenxid */
 	pg_time_t	time;			/* time stamp of checkpoint */
 
-	/* Important parameter settings at time of shutdown checkpoints */
-	int			MaxConnections;
-	int			max_prepared_xacts;
-	int			max_locks_per_xact;
-	bool		XLogStandbyInfoMode;
-
 	/*
 	 * Oldest XID still running. This is only needed to initialize hot standby
 	 * mode from an online checkpoint, so we only bother calculating this for
@@ -63,7 +57,7 @@ typedef struct CheckPoint
 #define XLOG_NEXTOID					0x30
 #define XLOG_SWITCH						0x40
 #define XLOG_BACKUP_END					0x50
-#define XLOG_UNLOGGED					0x60
+#define XLOG_PARAMETER_CHANGE			0x60
 
 
 /* System status indicator */
@@ -142,6 +136,15 @@ typedef struct ControlFileData
 	XLogRecPtr	backupStartPoint;
 
 	/*
+	 * Parameter settings that determine if the WAL can be used for archival
+	 * or hot standby.
+	 */
+	int			wal_level;
+	int			MaxConnections;
+	int			max_prepared_xacts;
+	int			max_locks_per_xact;
+
+	/*
 	 * This data is used to check for hardware-architecture compatibility of
 	 * the database and the backend executable.  We need not check endianness
 	 * explicitly, since the pg_control version will surely look wrong to a
diff --git a/src/include/replication/walsender.h b/src/include/replication/walsender.h
index abb8312ecf..d43ad912e7 100644
--- a/src/include/replication/walsender.h
+++ b/src/include/replication/walsender.h
@@ -5,7 +5,7 @@
  *
  * Portions Copyright (c) 2010-2010, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/include/replication/walsender.h,v 1.2 2010/02/26 02:01:27 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/replication/walsender.h,v 1.3 2010/04/28 16:10:43 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -39,6 +39,7 @@ extern bool am_walsender;
 
 /* user-settable parameters */
 extern int	WalSndDelay;
+extern int	max_wal_senders;
 
 extern int	WalSenderMain(void);
 extern void WalSndSignals(void);