Make CheckRequiredParameterValues() depend upon correct combination

of parameters. Fix bug report by Robert Haas that error message and
hint was incorrect if wrong mode parameters specified on master.
Internal changes only. Proposals for parameter simplification on
master/primary still under way.

Author: simonat2ndQuadrant

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.401 2010/04/20 11:15:06 rhaas Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.402 2010/04/23 19:57:18 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -5568,7 +5568,12 @@ CheckRequiredParameterValues(CheckPoint checkPoint)
 	RecoveryRequiresIntParameter("max_locks_per_xact",
 						  max_locks_per_xact, checkPoint.max_locks_per_xact);
 
-	if (!checkPoint.XLogStandbyInfoMode)
+	/*
+	 * Hot Standby currently only depends upon the presence of WAL
+	 * records as indicated by XLOG_MODE_HOT_STANDBY. There is no current
+	 * dependency on whether archiving or streaming are enabled, if either.
+	 */
+	if (!(checkPoint.XLogModeFlags & XLOG_MODE_HOT_STANDBY))
 		ereport(ERROR,
 				(errmsg("recovery connections cannot start because the recovery_connections "
 						"parameter is disabled on the WAL source server")));
@@ -7002,7 +7007,13 @@ CreateCheckPoint(int flags)
 	checkPoint.MaxConnections = MaxConnections;
 	checkPoint.max_prepared_xacts = max_prepared_xacts;
 	checkPoint.max_locks_per_xact = max_locks_per_xact;
-	checkPoint.XLogStandbyInfoMode = XLogStandbyInfoActive();
+
+	if (XLogArchivingActive())
+		checkPoint.XLogModeFlags |= XLOG_MODE_ARCHIVING;
+	if (max_wal_senders > 0)
+		checkPoint.XLogModeFlags |= XLOG_MODE_STREAMING;
+	if (XLogRequestRecoveryConnections)
+		checkPoint.XLogModeFlags |= XLOG_MODE_HOT_STANDBY;
 
 	/*
 	 * We must hold WALInsertLock while examining insert state to determine

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 1.51 2010/02/26 02:01:21 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_control.h,v 1.52 2010/04/23 19:57:19 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -45,7 +45,7 @@ typedef struct CheckPoint
 	int			MaxConnections;
 	int			max_prepared_xacts;
 	int			max_locks_per_xact;
-	bool		XLogStandbyInfoMode;
+	int			XLogModeFlags;
 
 	/*
 	 * Oldest XID still running. This is only needed to initialize hot standby
@@ -65,6 +65,10 @@ typedef struct CheckPoint
 #define XLOG_BACKUP_END					0x50
 #define XLOG_UNLOGGED					0x60
 
+/* XLogModeFlags */
+#define XLOG_MODE_ARCHIVING				(1 << 0)
+#define XLOG_MODE_STREAMING				(1 << 1)
+#define XLOG_MODE_HOT_STANDBY			(1 << 2)
 
 /* System status indicator */
 typedef enum DBState