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.

1 files changed, 26 insertions, 2 deletions

diff --git a/src/bin/pg_controldata/pg_controldata.c b/src/bin/pg_controldata/pg_controldata.c
index 2735a6611e..839de98842 100644
--- a/src/bin/pg_controldata/pg_controldata.c
+++ b/src/bin/pg_controldata/pg_controldata.c
@@ -6,15 +6,16 @@
  * copyright (c) Oliver Elphick <olly@lfix.co.uk>, 2001;
  * licence: BSD
  *
- * $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.46 2010/01/04 12:50:49 heikki Exp $
+ * $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.47 2010/04/28 16:10:43 heikki Exp $
  */
-#include "postgres_fe.h"
+#include "postgres.h"
 
 #include <unistd.h>
 #include <time.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 
+#include "access/xlog.h"
 #include "catalog/pg_control.h"
 
 
@@ -60,6 +61,21 @@ dbState(DBState state)
 	return _("unrecognized status code");
 }
 
+static const char *
+wal_level_str(WalLevel wal_level)
+{
+	switch (wal_level)
+	{
+		case WAL_LEVEL_MINIMAL:
+			return "minimal";
+		case WAL_LEVEL_ARCHIVE:
+			return "archive";
+		case WAL_LEVEL_HOT_STANDBY:
+			return "hot_standby";
+	}
+	return _("unrecognized wal_level");
+}
+
 
 int
 main(int argc, char *argv[])
@@ -206,6 +222,14 @@ main(int argc, char *argv[])
 	printf(_("Backup start location:                %X/%X\n"),
 		   ControlFile.backupStartPoint.xlogid,
 		   ControlFile.backupStartPoint.xrecoff);
+	printf(_("Last wal_level setting:               %s\n"),
+		   wal_level_str(ControlFile.wal_level));
+	printf(_("Last max_connections setting:         %d\n"),
+		   ControlFile.MaxConnections);
+	printf(_("Last max_prepared_xacts setting:      %d\n"),
+		   ControlFile.max_prepared_xacts);
+	printf(_("Last max_locks_per_xact setting:      %d\n"),
+		   ControlFile.max_locks_per_xact);
 	printf(_("Maximum data alignment:               %u\n"),
 		   ControlFile.maxAlign);
 	/* we don't print floatFormat since can't say much useful about it */