Implement COMMIT_SIBLINGS parameter to allow pre-commit delay to occur

only if at least N other backends currently have open transactions.  This
is not a great deal of intelligence about whether a delay might be
profitable ... but it beats no intelligence at all.  Note that the default
COMMIT_DELAY is still zero --- this new code does nothing unless that
setting is changed.
Also, mark ENABLEFSYNC as a system-wide setting.  It's no longer safe to
allow that to be set per-backend, since we may be relying on some other
backend's fsync to have synced the WAL log.

src/backend/utils/misc/guc.c

@@ -4,7 +4,7 @@
  * Support for grand unified configuration scheme, including SET
  * command, configuration file, and command line options.
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.30 2001/02/18 04:50:43 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.31 2001/02/26 00:50:07 tgl Exp $
  *
  * Copyright 2000 by PostgreSQL Global Development Group
  * Written by Peter Eisentraut <peter_e@gmx.net>.
@@ -41,6 +41,7 @@ extern int XLOGbuffers;
 extern int XLOGfiles;
 extern int XLOG_DEBUG;
 extern int CommitDelay;
+extern int CommitSiblings;
 
 extern bool FixBTree;
 
@@ -181,7 +182,7 @@ ConfigureNamesBool[] =
 
 	{"tcpip_socket",            PGC_POSTMASTER, &NetServer,             false},
 	{"ssl",                     PGC_POSTMASTER, &EnableSSL,             false},
-	{"fsync",                   PGC_USERSET,    &enableFsync,           true},
+	{"fsync",                   PGC_SIGHUP,     &enableFsync,           true},
 	{"silent_mode",             PGC_POSTMASTER, &SilentMode,            false},
 
 	{"log_connections",         PGC_SIGHUP,     &Log_connections,       false},
@@ -279,7 +280,7 @@ ConfigureNamesInt[] =
 	 0777, 0000, 0777},
 
 	{"checkpoint_timeout",	PGC_POSTMASTER,			&CheckPointTimeout,
-	 300, 30, 1800},
+	 300, 30, 3600},
 
 	{"wal_buffers",			PGC_POSTMASTER,			&XLOGbuffers,
 	 8, 4, INT_MAX},
@@ -293,6 +294,9 @@ ConfigureNamesInt[] =
 	{"commit_delay",		PGC_USERSET,			&CommitDelay,
 	 0, 0, 100000},
 
+	{"commit_siblings",		PGC_USERSET,			&CommitSiblings,
+	 5, 1, 1000},
+
 	{NULL, 0, NULL, 0, 0, 0}
 };
 

src/backend/utils/misc/postgresql.conf.sample

@@ -109,7 +109,8 @@
 #wal_files = 0 # range 0-64
 #wal_debug = 0 # range 0-16
 #commit_delay = 0 # range 0-100000
-#checkpoint_timeout = 300 # range 30-1800
+#commit_siblings = 5 # range 1-1000
+#checkpoint_timeout = 300 # in seconds, range 30-3600
 
 
 #