Add GUC full_page_writes to control writing full pages to WAL.

3 files changed, 20 insertions, 3 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index d42aa93c54..86e1e6878b 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.206 2005/07/04 04:51:44 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.207 2005/07/05 23:18:09 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -103,6 +103,7 @@ int			XLOGbuffers = 8;
 char	   *XLogArchiveCommand = NULL;
 char	   *XLOG_sync_method = NULL;
 const char	XLOG_sync_method_default[] = DEFAULT_SYNC_METHOD_STR;
+bool		fullPageWrites = true;
 
 #ifdef WAL_DEBUG
 bool		XLOG_DEBUG = false;
@@ -594,7 +595,9 @@ begin:;
 				{
 					/* OK, put it in this slot */
 					dtbuf[i] = rdt->buffer;
-					if (XLogCheckBuffer(rdt, &(dtbuf_lsn[i]), &(dtbuf_xlg[i])))
+					/* If fsync is off, no need to backup pages. */
+					if (fullPageWrites &&
+						XLogCheckBuffer(rdt, &(dtbuf_lsn[i]), &(dtbuf_xlg[i])))
 					{
 						dtbuf_bkp[i] = true;
 						rdt->data = NULL;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 0ea335770c..ca59f6755b 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.272 2005/07/04 04:51:51 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.273 2005/07/05 23:18:10 momjian Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -83,6 +83,7 @@ extern DLLIMPORT bool check_function_bodies;
 extern int	CommitDelay;
 extern int	CommitSiblings;
 extern char *default_tablespace;
+extern bool	fullPageWrites;
 
 static const char *assign_log_destination(const char *value,
 					   bool doit, GucSource source);
@@ -483,6 +484,18 @@ static struct config_bool ConfigureNamesBool[] =
 		false, NULL, NULL
 	},
 	{
+		{"full_page_writes", PGC_SIGHUP, WAL_SETTINGS,
+			gettext_noop("Writes full pages to WAL when first modified after a checkpoint."),
+			gettext_noop("A page write in process during an operating system crash might be "
+						 "only partially written to disk.  During recovery, the row changes"
+						 "stored in WAL are not enough to recover.  This option writes "
+						 "pages when first modified after a checkpoint to WAL so full recovery "
+						 "is possible.")
+		},
+		&fullPageWrites,
+		true, NULL, NULL
+	},
+	{
 		{"silent_mode", PGC_POSTMASTER, LOGGING_WHEN,
 			gettext_noop("Runs the server silently."),
 			gettext_noop("If this parameter is set, the server will automatically run in the "
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 4e7c9207dd..193b0303b3 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -121,6 +121,7 @@
 #wal_sync_method = fsync	# the default varies across platforms:
 				# fsync, fdatasync, fsync_writethrough,
 				# open_sync, open_datasync
+#full_page_writes = on		# recover from partial page writes
 #wal_buffers = 8		# min 4, 8KB each
 #commit_delay = 0		# range 0-100000, in microseconds
 #commit_siblings = 5		# range 1-1000