Index: src/backend/access/transam/xact.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/access/transam/xact.c,v
retrieving revision 1.234
diff -c -r1.234 xact.c
*** src/backend/access/transam/xact.c	9 Feb 2007 03:35:33 -0000	1.234
--- src/backend/access/transam/xact.c	11 Mar 2007 22:37:09 -0000
***************
*** 58,63 ****
--- 58,66 ----
  int			CommitDelay = 0;	/* precommit delay in microseconds */
  int			CommitSiblings = 5; /* # concurrent xacts needed to sleep */
  
+ bool			DefaultXactCommitGuarantee = true;  /* USERSET GUC: what user wants */
+ static bool		XactCommitGuarantee = true;	     	/* the guarantee for this Xid? */
+ bool			log_transaction_guarantee = true;
  
  /*
   *	transaction states - transaction state from server perspective
***************
*** 710,715 ****
--- 713,719 ----
  		TransactionId xid = GetCurrentTransactionId();
  		bool		madeTCentries;
  		XLogRecPtr	recptr;
+ 		bool 		unsafe = false;
  
  		/* Tell bufmgr and smgr to prepare for commit */
  		BufmgrCommit();
***************
*** 792,812 ****
  		if (MyXactMadeXLogEntry)
  		{
  			/*
! 			 * Sleep before flush! So we can flush more than one commit
! 			 * records per single fsync.  (The idea is some other backend may
! 			 * do the XLogFlush while we're sleeping.  This needs work still,
! 			 * because on most Unixen, the minimum select() delay is 10msec or
! 			 * more, which is way too long.)
! 			 *
! 			 * We do not sleep if enableFsync is not turned on, nor if there
! 			 * are fewer than CommitSiblings other backends with active
! 			 * transactions.
! 			 */
! 			if (CommitDelay > 0 && enableFsync &&
! 				CountActiveBackends() >= CommitSiblings)
! 				pg_usleep(CommitDelay);
  
! 			XLogFlush(recptr);
  		}
  
  		/*
--- 796,830 ----
  		if (MyXactMadeXLogEntry)
  		{
  			/*
! 			 * If we have chosen to use unguaranteed transactions and we're
! 			 * not doing cleanup of any rels, then we can defer fsync.
! 			 * The WAL writer acts to minimise the window of data loss,
! 			 * and we rely on it to flush WAL soon, but not precisely now.
! 			 */
! 			if (XactCommitGuarantee || nrels > 0)
! 			{
! 				/*
! 				 * Sleep before flush! So we can flush more than one commit
! 				 * records per single fsync.  (The idea is some other backend may
! 				 * do the XLogFlush while we're sleeping.  This needs work still,
! 				 * because on most Unixen, the minimum select() delay is 10msec or
! 				 * more, which is way too long.)
! 				 *
! 				 * We do not sleep if enableFsync is not turned on, nor if there
! 				 * are fewer than CommitSiblings other backends with active
! 				 * transactions.
! 				 */
! 				if (CommitDelay > 0 && enableFsync &&
! 					CountActiveBackends() >= CommitSiblings)
! 					pg_usleep(CommitDelay);
  
! 				XLogFlush(recptr);
! 			}
! 			else
! 			{
! 				unsafe = true;
! 				XLogDeferredFlush(recptr);
! 			}
  		}
  
  		/*
***************
*** 830,835 ****
--- 848,858 ----
  			LWLockRelease(CheckpointStartLock);
  
  		END_CRIT_SECTION();
+ 
+ 		if (log_transaction_guarantee && madeTCentries && WALWriterActive())
+ 			elog(LOG,"COMMIT %s insert %X/%X", 
+ 				(XactCommitGuarantee ? "  safe" : "unsafe"),
+ 				 recptr.xlogid, recptr.xrecoff);
  	}
  
  	/* Break the chain of back-links in the XLOG records I output */
***************
*** 1388,1393 ****
--- 1411,1417 ----
  	FreeXactSnapshot();
  	XactIsoLevel = DefaultXactIsoLevel;
  	XactReadOnly = DefaultXactReadOnly;
+ 	SetXactCommitGuarantee(true);
  
  	/*
  	 * reinitialize within-transaction counters
***************
*** 4092,4097 ****
--- 4116,4127 ----
  	return "UNRECOGNIZED";
  }
  
+ void
+ SetXactCommitGuarantee(bool RequestedXactCommitGuarantee)
+ {
+ 	XactCommitGuarantee = RequestedXactCommitGuarantee;
+ }
+ 
  /*
   * xactGetCommittedChildren
   *
Index: src/backend/access/transam/xlog.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/access/transam/xlog.c,v
retrieving revision 1.265
diff -c -r1.265 xlog.c
*** src/backend/access/transam/xlog.c	3 Mar 2007 20:02:26 -0000	1.265
--- src/backend/access/transam/xlog.c	11 Mar 2007 22:37:15 -0000
***************
*** 301,306 ****
--- 301,309 ----
  	/* Protected by WALWriteLock: */
  	XLogCtlWrite Write;
  
+ 	/* Protected by commit_lck: */
+ 	XLogwrtRqst	CommitLogwrtRqst;
+ 
  	/*
  	 * These values do not change after startup, although the pointed-to pages
  	 * and xlblocks values certainly do.  Permission to read/write the pages
***************
*** 313,318 ****
--- 316,322 ----
  	TimeLineID	ThisTimeLineID;
  
  	slock_t		info_lck;		/* locks shared variables shown above */
+ 	slock_t		commit_lck;		/* deferred commit lock */
  } XLogCtlData;
  
  static XLogCtlData *XLogCtl = NULL;
***************
*** 1787,1792 ****
--- 1791,1851 ----
  }
  
  /*
+  * XLogDeferredFlush
+  *
+  * Keep track of deferred flush requests by unguaranteed transaction commits
+  */
+ void 
+ XLogDeferredFlush(XLogRecPtr RecPtr)
+ {
+ 	/*
+ 	 * Update the deferred commit request pointer, if required, then
+ 	 * return quickly so we can do some other useful work
+ 	 */
+ 	{
+ 		/* use volatile pointer to prevent code rearrangement */
+ 		volatile XLogCtlData *xlogctl = XLogCtl;
+ 
+ 		SpinLockAcquire(&xlogctl->commit_lck);
+ 		if (!XLByteLE(xlogctl->CommitLogwrtRqst.Write, RecPtr))
+ 			xlogctl->CommitLogwrtRqst.Write = RecPtr;
+ 		SpinLockRelease(&xlogctl->commit_lck);
+ 	}
+ 
+ 	/* Note that there is *no* XLogFlush() here, by design */
+ }
+ 
+ /*
+  * XLogBackgroundFlush
+  * 
+  * Flush as far as the deferred commit request pointer, so that all
+  * unguaranteed commits are known flushed after this returns.
+  *
+  * If it hasn't changed or a normal commit has flushed past our pointer
+  * we will exit quickly from XLogFlush(), so no extra code here
+  */
+ void
+ XLogBackgroundFlush(void)
+ {
+ 	XLogRecPtr RecPtr;
+ 
+ 	/*
+ 	 * Get the current deferred commit request pointer,
+ 	 * don't worry about keeping local state information
+ 	 */
+ 	{
+ 		/* use volatile pointer to prevent code rearrangement */
+ 		volatile XLogCtlData *xlogctl = XLogCtl;
+ 
+ 		SpinLockAcquire(&xlogctl->commit_lck);
+ 		RecPtr = xlogctl->CommitLogwrtRqst.Write;
+ 		SpinLockRelease(&xlogctl->commit_lck);
+ 	}
+ 
+ 	XLogFlush(RecPtr);
+ }
+ 
+ /*
   * Create a new XLOG file segment, or open a pre-existing one.
   *
   * log, seg: identify segment to be created/opened.
***************
*** 3985,3990 ****
--- 4044,4050 ----
  	XLogCtl->XLogCacheBlck = XLOGbuffers - 1;
  	XLogCtl->Insert.currpage = (XLogPageHeader) (XLogCtl->pages);
  	SpinLockInit(&XLogCtl->info_lck);
+ 	SpinLockInit(&XLogCtl->commit_lck);
  
  	/*
  	 * If we are not in bootstrap mode, pg_control should already exist. Read
***************
*** 4998,5003 ****
--- 5058,5065 ----
  
  	XLogCtl->LogwrtRqst.Write = EndOfLog;
  	XLogCtl->LogwrtRqst.Flush = EndOfLog;
+ 	XLogCtl->CommitLogwrtRqst.Write = EndOfLog;
+ 	XLogCtl->CommitLogwrtRqst.Flush = EndOfLog;
  
  	freespace = INSERT_FREESPACE(Insert);
  	if (freespace > 0)
***************
*** 5389,5394 ****
--- 5451,5463 ----
  	 */
  	LWLockAcquire(CheckpointStartLock, LW_EXCLUSIVE);
  
+ 	/*
+ 	 * Now confirm that all unguaranteed transactions are written to WAL
+ 	 * before we proceed further. This may require WALWriteLock and possibly
+ 	 * WALInsertLock if we need to flush.
+ 	 */
+ 	XLogBackgroundFlush();
+ 
  	/* And we need WALInsertLock too */
  	LWLockAcquire(WALInsertLock, LW_EXCLUSIVE);
  
Index: src/backend/postmaster/Makefile
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/postmaster/Makefile,v
retrieving revision 1.22
diff -c -r1.22 Makefile
*** src/backend/postmaster/Makefile	20 Jan 2007 17:16:12 -0000	1.22
--- src/backend/postmaster/Makefile	11 Mar 2007 22:37:17 -0000
***************
*** 12,18 ****
  top_builddir = ../../..
  include $(top_builddir)/src/Makefile.global
  
! OBJS = bgwriter.o autovacuum.o pgarch.o pgstat.o postmaster.o syslogger.o \
  	fork_process.o
  
  all: SUBSYS.o
--- 12,18 ----
  top_builddir = ../../..
  include $(top_builddir)/src/Makefile.global
  
! OBJS = bgwriter.o walwriter.o autovacuum.o pgarch.o pgstat.o postmaster.o syslogger.o \
  	fork_process.o
  
  all: SUBSYS.o
Index: src/backend/postmaster/postmaster.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/postmaster/postmaster.c,v
retrieving revision 1.526
diff -c -r1.526 postmaster.c
*** src/backend/postmaster/postmaster.c	7 Mar 2007 13:35:02 -0000	1.526
--- src/backend/postmaster/postmaster.c	11 Mar 2007 22:37:21 -0000
***************
*** 107,112 ****
--- 107,113 ----
  #include "postmaster/pgarch.h"
  #include "postmaster/postmaster.h"
  #include "postmaster/syslogger.h"
+ #include "postmaster/walwriter.h"
  #include "storage/fd.h"
  #include "storage/ipc.h"
  #include "storage/pg_shmem.h"
***************
*** 201,206 ****
--- 202,208 ----
  /* PIDs of special child processes; 0 when not running */
  static pid_t StartupPID = 0,
  			BgWriterPID = 0,
+ 			WALWriterPID = 0,
  			AutoVacPID = 0,
  			PgArchPID = 0,
  			PgStatPID = 0;
***************
*** 907,913 ****
  	 * CAUTION: when changing this list, check for side-effects on the signal
  	 * handling setup of child processes.  See tcop/postgres.c,
  	 * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/autovacuum.c,
! 	 * postmaster/pgarch.c, postmaster/pgstat.c, and postmaster/syslogger.c.
  	 */
  	pqinitmask();
  	PG_SETMASK(&BlockSig);
--- 909,916 ----
  	 * CAUTION: when changing this list, check for side-effects on the signal
  	 * handling setup of child processes.  See tcop/postgres.c,
  	 * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/autovacuum.c,
! 	 * postmaster/pgarch.c, postmaster/pgstat.c, postmaster/syslogger.c
! 	 * and postmaster/walwriter.c
  	 */
  	pqinitmask();
  	PG_SETMASK(&BlockSig);
***************
*** 1250,1255 ****
--- 1253,1263 ----
  				start_autovac_launcher = false;	/* signal successfully processed */
  		}
  
+ 		/* If we have lost the WAL writer, try to start a new one */
+ 		if (WALWriterActive() && WALWriterPID == 0 &&
+ 			StartupPID == 0 && !FatalError && Shutdown == NoShutdown)
+ 			WALWriterPID = StartWALWriter();
+ 
  		/* If we have lost the archiver, try to start a new one */
  		if (XLogArchivingActive() && PgArchPID == 0 &&
  			StartupPID == 0 && !FatalError && Shutdown == NoShutdown)
***************
*** 1822,1827 ****
--- 1830,1837 ----
  			signal_child(BgWriterPID, SIGHUP);
  		if (AutoVacPID != 0)
  			signal_child(AutoVacPID, SIGHUP);
+ 		if (WALWriterPID != 0)
+ 			signal_child(WALWriterPID, SIGHUP);
  		if (PgArchPID != 0)
  			signal_child(PgArchPID, SIGHUP);
  		if (SysLoggerPID != 0)
***************
*** 1891,1896 ****
--- 1901,1909 ----
  			/* And tell it to shut down */
  			if (BgWriterPID != 0)
  				signal_child(BgWriterPID, SIGUSR2);
+ 			/* Tell WALWriter to shut down too; nothing left for it to do */
+ 			if (WALWriterPID != 0)
+ 				signal_child(WALWriterPID, SIGQUIT);
  			/* Tell pgarch to shut down too; nothing left for it to do */
  			if (PgArchPID != 0)
  				signal_child(PgArchPID, SIGQUIT);
***************
*** 1947,1952 ****
--- 1960,1968 ----
  			/* And tell it to shut down */
  			if (BgWriterPID != 0)
  				signal_child(BgWriterPID, SIGUSR2);
+ 			/* Tell WALWriter to shut down too; nothing left for it to do */
+ 			if (WALWriterPID != 0)
+ 				signal_child(WALWriterPID, SIGQUIT);
  			/* Tell pgarch to shut down too; nothing left for it to do */
  			if (PgArchPID != 0)
  				signal_child(PgArchPID, SIGQUIT);
***************
*** 1972,1977 ****
--- 1988,1995 ----
  				signal_child(StartupPID, SIGQUIT);
  			if (BgWriterPID != 0)
  				signal_child(BgWriterPID, SIGQUIT);
+ 			if (WALWriterPID != 0)
+ 				signal_child(WALWriterPID, SIGQUIT);
  			if (AutoVacPID != 0)
  				signal_child(AutoVacPID, SIGQUIT);
  			if (PgArchPID != 0)
***************
*** 2070,2077 ****
  
  			/*
  			 * Go to shutdown mode if a shutdown request was pending.
! 			 * Otherwise, try to start the archiver, stats collector and
! 			 * autovacuum launcher.
  			 */
  			if (Shutdown > NoShutdown && BgWriterPID != 0)
  				signal_child(BgWriterPID, SIGUSR2);
--- 2088,2095 ----
  
  			/*
  			 * Go to shutdown mode if a shutdown request was pending.
! 			 * Otherwise, try to start the archiver, stats collector,
! 			 * autovacuum launcher and WALWriter.
  			 */
  			if (Shutdown > NoShutdown && BgWriterPID != 0)
  				signal_child(BgWriterPID, SIGUSR2);
***************
*** 2081,2086 ****
--- 2099,2106 ----
  					PgArchPID = pgarch_start();
  				if (PgStatPID == 0)
  					PgStatPID = pgstat_start();
+ 				if (WALWriterPID == 0)
+ 					WALWriterPID = StartWALWriter();
  				if (AutoVacuumingActive() && AutoVacPID == 0)
  					AutoVacPID = StartAutoVacLauncher();
  
***************
*** 2141,2146 ****
--- 2161,2180 ----
  		}
  
  		/*
+ 		 * Was it the WALWriter?  Normal exit can be ignored; we'll
+ 		 * start a new one at the next iteration of the postmaster's main loop,
+ 		 * if necessary.  Any other exit condition is treated as a crash.
+ 		 */
+ 		if (WALWriterPID != 0 && pid == WALWriterPID)
+ 		{
+ 			WALWriterPID = 0;
+ 			if (!EXIT_STATUS_0(exitstatus))
+ 				HandleChildCrash(pid, exitstatus,
+ 								 _("WALWriter process"));
+ 			continue;
+ 		}
+ 
+ 		/*
  		 * Was it the autovacuum launcher?  Normal exit can be ignored; we'll
  		 * start a new one at the next iteration of the postmaster's main loop,
  		 * if necessary.  Any other exit condition is treated as a crash.
***************
*** 2236,2241 ****
--- 2270,2278 ----
  		/* And tell it to shut down */
  		if (BgWriterPID != 0)
  			signal_child(BgWriterPID, SIGUSR2);
+ 		/* Tell WALWriter to shut down too; nothing left for it to do */
+ 		if (WALWriterPID != 0)
+ 			signal_child(WALWriterPID, SIGQUIT);
  		/* Tell pgarch to shut down too; nothing left for it to do */
  		if (PgArchPID != 0)
  			signal_child(PgArchPID, SIGQUIT);
***************
*** 2384,2389 ****
--- 2421,2437 ----
  		signal_child(AutoVacPID, (SendStop ? SIGSTOP : SIGQUIT));
  	}
  
+ 	/* Force a power-cycle of the WALWriter process too */
+ 	/* (Shouldn't be necessary, but just for luck) */
+ 	if (WALWriterPID != 0 && !FatalError)
+ 	{
+ 		ereport(DEBUG2,
+ 				(errmsg_internal("sending %s to process %d",
+ 								 "SIGQUIT",
+ 								 (int) WALWriterPID)));
+ 		signal_child(WALWriterPID, SIGQUIT);
+ 	}
+ 
  	/* Force a power-cycle of the pgarch process too */
  	/* (Shouldn't be necessary, but just for luck) */
  	if (PgArchPID != 0 && !FatalError)
***************
*** 3475,3480 ****
--- 3523,3545 ----
  		AutoVacWorkerMain(argc - 2, argv + 2);
  		proc_exit(0);
  	}
+ 	if (strcmp(argv[1], "--forkwalwriter") == 0)
+ 	{
+ 		/* Close the postmaster's sockets */
+ 		ClosePostmasterPorts(false);
+ 
+ 		/* Restore basic shared memory pointers */
+ 		InitShmemAccess(UsedShmemSegAddr);
+ 
+ 		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
+ 		InitProcess();
+ 
+ 		/* Attach process to shared data structures */
+ 		CreateSharedMemoryAndSemaphores(false, 0);
+ 
+ 		WALWriterMain(argc, argv);
+ 		proc_exit(0);
+ 	}
  	if (strcmp(argv[1], "--forkarch") == 0)
  	{
  		/* Close the postmaster's sockets */
Index: src/backend/tcop/postgres.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/tcop/postgres.c,v
retrieving revision 1.527
diff -c -r1.527 postgres.c
*** src/backend/tcop/postgres.c	3 Mar 2007 19:32:54 -0000	1.527
--- src/backend/tcop/postgres.c	11 Mar 2007 22:37:24 -0000
***************
*** 2224,2229 ****
--- 2224,2231 ----
  		ereport(DEBUG3,
  				(errmsg_internal("CommitTransactionCommand")));
  
+ 		SetXactCommitGuarantee(DefaultXactCommitGuarantee);
+ 
  		CommitTransactionCommand();
  
  #ifdef MEMORY_CONTEXT_CHECKING
Index: src/backend/utils/misc/guc.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/guc.c,v
retrieving revision 1.379
diff -c -r1.379 guc.c
*** src/backend/utils/misc/guc.c	6 Mar 2007 02:06:14 -0000	1.379
--- src/backend/utils/misc/guc.c	11 Mar 2007 22:37:31 -0000
***************
*** 52,57 ****
--- 52,58 ----
  #include "postmaster/bgwriter.h"
  #include "postmaster/postmaster.h"
  #include "postmaster/syslogger.h"
+ #include "postmaster/walwriter.h"
  #include "storage/fd.h"
  #include "storage/freespace.h"
  #include "tcop/tcopprot.h"
***************
*** 100,105 ****
--- 101,107 ----
  extern int	CommitSiblings;
  extern char *default_tablespace;
  extern bool fullPageWrites;
+ extern bool log_transaction_guarantee;
  
  #ifdef TRACE_SORT
  extern bool trace_sort;
***************
*** 145,150 ****
--- 147,153 ----
  static bool assign_stage_log_stats(bool newval, bool doit, GucSource source);
  static bool assign_log_stats(bool newval, bool doit, GucSource source);
  static bool assign_transaction_read_only(bool newval, bool doit, GucSource source);
+ static bool assign_transaction_guarantee(bool newval, bool doit, GucSource source);
  static const char *assign_canonical_path(const char *newval, bool doit, GucSource source);
  static const char *assign_backslash_quote(const char *newval, bool doit, GucSource source);
  static const char *assign_timezone_abbreviations(const char *newval, bool doit, GucSource source);
***************
*** 312,317 ****
--- 315,322 ----
  	gettext_noop("Write-Ahead Log"),
  	/* WAL_SETTINGS */
  	gettext_noop("Write-Ahead Log / Settings"),
+ 	/* WAL_COMMITS */
+ 	gettext_noop("Write-Ahead Log / Commit Behavior"),
  	/* WAL_CHECKPOINTS */
  	gettext_noop("Write-Ahead Log / Checkpoints"),
  	/* QUERY_TUNING */
***************
*** 568,573 ****
--- 573,586 ----
  		false, NULL, NULL
  	},
  	{
+ 		{"log_transaction_guarantee", PGC_SIGHUP, WAL_COMMITS,
+ 			gettext_noop("Logs form of guarantee used at transaction commit."),
+ 			NULL
+ 		},
+ 		&log_transaction_guarantee,
+ 		true, NULL, NULL
+ 	},
+ 	{
  		{"log_connections", PGC_BACKEND, LOGGING_WHAT,
  			gettext_noop("Logs each successful connection."),
  			NULL
***************
*** 878,883 ****
--- 891,904 ----
  		true, assign_phony_autocommit, NULL
  	},
  	{
+ 		{"transaction_guarantee", PGC_USERSET, WAL_COMMITS,
+ 			gettext_noop("Sets the default of wait-for-commit."),
+ 			NULL
+ 		},
+ 		&DefaultXactCommitGuarantee,
+ 		true, assign_transaction_guarantee, NULL
+ 	},
+ 	{
  		{"default_transaction_read_only", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the default read-only status of new transactions."),
  			NULL
***************
*** 1452,1458 ****
  	},
  
  	{
! 		{"commit_delay", PGC_USERSET, WAL_CHECKPOINTS,
  			gettext_noop("Sets the delay in microseconds between transaction commit and "
  						 "flushing WAL to disk."),
  			NULL
--- 1473,1479 ----
  	},
  
  	{
! 		{"commit_delay", PGC_USERSET, WAL_COMMITS,
  			gettext_noop("Sets the delay in microseconds between transaction commit and "
  						 "flushing WAL to disk."),
  			NULL
***************
*** 1462,1468 ****
  	},
  
  	{
! 		{"commit_siblings", PGC_USERSET, WAL_CHECKPOINTS,
  			gettext_noop("Sets the minimum concurrent open transactions before performing "
  						 "commit_delay."),
  			NULL
--- 1483,1489 ----
  	},
  
  	{
! 		{"commit_siblings", PGC_USERSET, WAL_COMMITS,
  			gettext_noop("Sets the minimum concurrent open transactions before performing "
  						 "commit_delay."),
  			NULL
***************
*** 1472,1477 ****
--- 1493,1507 ----
  	},
  
  	{
+ 		{"wal_writer_delay", PGC_SIGHUP, WAL_COMMITS,
+ 			gettext_noop("Sets the delay in microseconds between regular flushing of WAL "
+ 						 "to disk by the WALWriter."),
+ 			NULL
+ 		},
+ 		&WALWriterDelay,
+ 		0, 0, 10000000, NULL, NULL
+ 	},
+ 	{
  		{"extra_float_digits", PGC_USERSET, CLIENT_CONN_LOCALE,
  			gettext_noop("Sets the number of digits displayed for floating-point values."),
  			gettext_noop("This affects real, double precision, and geometric data types. "
***************
*** 6430,6435 ****
--- 6460,6484 ----
  	return true;
  }
  
+ static bool
+ assign_transaction_guarantee(bool newval, bool doit, GucSource source)
+ {
+ 	/* 
+ 	 * Transaction guarantee can only be disabled if the
+ 	 * WALWriter has been activated, allowing us to place
+ 	 * a sensible time limit on the extent of the data loss window
+ 	 * for UnGuaranteed Transactions
+ 	 */
+ 	if (newval == false && !WALWriterActive())
+ 	{	
+ 		if (source >= PGC_S_INTERACTIVE)
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 					 errmsg("cannot set transaction guarantee when server commit_fsync_delay = 0")));
+ 	}
+ 	return true;
+ }
+ 
  static const char *
  assign_canonical_path(const char *newval, bool doit, GucSource source)
  {
Index: src/backend/utils/misc/postgresql.conf.sample
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/postgresql.conf.sample,v
retrieving revision 1.212
diff -c -r1.212 postgresql.conf.sample
*** src/backend/utils/misc/postgresql.conf.sample	6 Mar 2007 02:06:14 -0000	1.212
--- src/backend/utils/misc/postgresql.conf.sample	11 Mar 2007 22:37:31 -0000
***************
*** 150,156 ****
  
  # - Settings -
  
! #fsync = on				# turns forced synchronization on or off
  #wal_sync_method = fsync		# the default is the first option 
  					# supported by the operating system:
  					#   open_datasync
--- 150,156 ----
  
  # - Settings -
  
! #wal_writer_delay = 0			# range 0-10000000, in microseconds
  #wal_sync_method = fsync		# the default is the first option 
  					# supported by the operating system:
  					#   open_datasync
***************
*** 161,169 ****
--- 161,172 ----
  #full_page_writes = on			# recover from partial page writes
  #wal_buffers = 64kB			# min 32kB
  					# (change requires restart)
+ 
  #commit_delay = 0			# range 0-100000, in microseconds
  #commit_siblings = 5			# range 1-1000
  
+ #transaction_guarantee = on		# default: immediate fsync at commit
+ 
  # - Checkpoints -
  
  #checkpoint_segments = 3		# in logfile segments, min 1, 16MB each
Index: src/include/access/xact.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/include/access/xact.h,v
retrieving revision 1.84
diff -c -r1.84 xact.h
*** src/include/access/xact.h	5 Jan 2007 22:19:51 -0000	1.84
--- src/include/access/xact.h	11 Mar 2007 22:37:33 -0000
***************
*** 16,21 ****
--- 16,22 ----
  
  #include "access/xlog.h"
  #include "nodes/pg_list.h"
+ #include "postmaster/walwriter.h"
  #include "storage/relfilenode.h"
  #include "utils/timestamp.h"
  
***************
*** 41,46 ****
--- 42,50 ----
  extern bool DefaultXactReadOnly;
  extern bool XactReadOnly;
  
+ /* Deferred Fsync */
+ extern bool DefaultXactCommitGuarantee;
+ extern void SetXactCommitGuarantee(bool RequestedXactCommitGuarantee);
  /*
   *	start- and end-of-transaction callbacks for dynamically loaded modules
   */
Index: src/include/access/xlog.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/include/access/xlog.h,v
retrieving revision 1.76
diff -c -r1.76 xlog.h
*** src/include/access/xlog.h	5 Jan 2007 22:19:51 -0000	1.76
--- src/include/access/xlog.h	11 Mar 2007 22:37:33 -0000
***************
*** 151,156 ****
--- 151,158 ----
  
  extern XLogRecPtr XLogInsert(RmgrId rmid, uint8 info, XLogRecData *rdata);
  extern void XLogFlush(XLogRecPtr RecPtr);
+ extern void XLogDeferredFlush(XLogRecPtr RecPtr);
+ extern void XLogBackgroundFlush(void);
  
  extern void xlog_redo(XLogRecPtr lsn, XLogRecord *record);
  extern void xlog_desc(StringInfo buf, uint8 xl_info, char *rec);
Index: src/include/utils/guc_tables.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/include/utils/guc_tables.h,v
retrieving revision 1.30
diff -c -r1.30 guc_tables.h
*** src/include/utils/guc_tables.h	5 Jan 2007 22:19:59 -0000	1.30
--- src/include/utils/guc_tables.h	11 Mar 2007 22:37:34 -0000
***************
*** 51,56 ****
--- 51,57 ----
  	RESOURCES_KERNEL,
  	WAL,
  	WAL_SETTINGS,
+ 	WAL_COMMITS,
  	WAL_CHECKPOINTS,
  	QUERY_TUNING,
  	QUERY_TUNING_METHOD,