diff -Ncar postgresql-8.2.1.org/src/backend/access/transam/xlog.c postgresql-8.2.1/src/backend/access/transam/xlog.c
*** postgresql-8.2.1.org/src/backend/access/transam/xlog.c	2006-12-01 03:29:11.000000000 +0900
--- postgresql-8.2.1/src/backend/access/transam/xlog.c	2007-04-06 16:54:23.000000000 +0900
***************
*** 137,142 ****
--- 137,143 ----
  char	   *XLOG_sync_method = NULL;
  const char	XLOG_sync_method_default[] = DEFAULT_SYNC_METHOD_STR;
  bool		fullPageWrites = true;
+ bool		walAddOptimizationInfo = false;
  
  #ifdef WAL_DEBUG
  bool		XLOG_DEBUG = false;
***************
*** 626,632 ****
  				{
  					/* Buffer already referenced by earlier chain item */
  					if (dtbuf_bkp[i])
! 						rdt->data = NULL;
  					else if (rdt->data)
  					{
  						len += rdt->len;
--- 627,641 ----
  				{
  					/* Buffer already referenced by earlier chain item */
  					if (dtbuf_bkp[i])
! 					{
! 						if (fullPageWrites && walAddOptimizationInfo && rdt->data)
! 						{
! 							len += rdt->len;
! 							COMP_CRC32(rdata_crc, rdt->data, rdt->len);
! 						}
! 						else
! 							rdt->data = NULL;
! 					}
  					else if (rdt->data)
  					{
  						len += rdt->len;
***************
*** 642,648 ****
  										&(dtbuf_lsn[i]), &(dtbuf_xlg[i])))
  					{
  						dtbuf_bkp[i] = true;
! 						rdt->data = NULL;
  					}
  					else if (rdt->data)
  					{
--- 651,663 ----
  										&(dtbuf_lsn[i]), &(dtbuf_xlg[i])))
  					{
  						dtbuf_bkp[i] = true;
! 						if (fullPageWrites && walAddOptimizationInfo && rdt->data)
! 						{
! 							len += rdt->len;
! 							COMP_CRC32(rdata_crc, rdt->data, rdt->len);
! 						}
! 						else
! 							rdt->data = NULL;
  					}
  					else if (rdt->data)
  					{
***************
*** 908,913 ****
--- 923,941 ----
  		return RecPtr;
  	}
  
+ 	/*
+ 	 * If online backup is not in progress and wal_add_optimization_info is on, 
+ 	 * mark backup blocks removable if any.
+ 	 * This mark will be referenced during archiving to remove needless backup
+ 	 * blocks in the record and compress WAL segment files.
+ 	 * NOTE: wal_add_optimization_info is ignored when full_page_writes is off.
+ 	 */
+ 	if (fullPageWrites && walAddOptimizationInfo && (info & XLR_BKP_BLOCK_MASK) &&
+ 		!Insert->forcePageWrites)
+ 	{
+ 		info |= XLR_BKP_REMOVABLE;
+ 	}
+ 
  	/* Insert record header */
  
  	record = (XLogRecord *) Insert->currpos;
***************
*** 2820,2832 ****
  		blk += blen;
  	}
  
! 	/* Check that xl_tot_len agrees with our calculation */
! 	if (blk != (char *) record + record->xl_tot_len)
  	{
! 		ereport(emode,
! 				(errmsg("incorrect total length in record at %X/%X",
! 						recptr.xlogid, recptr.xrecoff)));
! 		return false;
  	}
  
  	/* Finally include the record header */
--- 2848,2876 ----
  		blk += blen;
  	}
  
! 	/*
! 	 * If physical log has not been removed, check the length to see
! 	 * the following.
! 	 *   - No physical log existed originally,
! 	 *   - WAL record was not removable because it is generated during
! 	 *     the online backup,
! 	 *   - Cannot be removed because the physical log spanned in
! 	 *     two segments.
! 	 * The reason why we skip the length check on the physical log removal is
! 	 * that the flag XLR_SET_BKB_BLOCK(0..2) is reset to zero and it prevents
! 	 * the above loop to proceed blk to the end of the record.
! 	 */
! 	if (!(record->xl_info & XLR_BKP_REMOVABLE) ||
! 		record->xl_info & XLR_BKP_BLOCK_MASK)
  	{
! 		/* Check that xl_tot_len agrees with our calculation */
! 		if (blk != (char *) record + record->xl_tot_len)
! 		{
! 			ereport(emode,
! 					(errmsg("incorrect total length in record at %X/%X",
! 							recptr.xlogid, recptr.xrecoff)));
! 			return false;
! 		}
  	}
  
  	/* Finally include the record header */
diff -Ncar postgresql-8.2.1.org/src/backend/utils/misc/guc.c postgresql-8.2.1/src/backend/utils/misc/guc.c
*** postgresql-8.2.1.org/src/backend/utils/misc/guc.c	2006-11-29 23:50:07.000000000 +0900
--- postgresql-8.2.1/src/backend/utils/misc/guc.c	2007-04-06 16:54:23.000000000 +0900
***************
*** 97,102 ****
--- 97,103 ----
  extern int	CommitSiblings;
  extern char *default_tablespace;
  extern bool fullPageWrites;
+ extern bool walAddOptimizationInfo;
  
  #ifdef TRACE_SORT
  extern bool trace_sort;
***************
*** 546,551 ****
--- 547,560 ----
  		true, NULL, NULL
  	},
  	{
+ 		{"wal_add_optimization_info", PGC_SIGHUP, WAL_SETTINGS,
+ 			gettext_noop("Writes logical log corresponding to full pages in WAL record."),
+ 			gettext_noop("")
+ 		},
+ 		&walAddOptimizationInfo,
+ 		false, 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 -Ncar postgresql-8.2.1.org/src/backend/utils/misc/postgresql.conf.sample postgresql-8.2.1/src/backend/utils/misc/postgresql.conf.sample
*** postgresql-8.2.1.org/src/backend/utils/misc/postgresql.conf.sample	2006-11-21 10:23:37.000000000 +0900
--- postgresql-8.2.1/src/backend/utils/misc/postgresql.conf.sample	2007-04-06 16:54:23.000000000 +0900
***************
*** 154,159 ****
--- 154,161 ----
  					#   fsync_writethrough
  					#   open_sync
  #full_page_writes = on			# recover from partial page writes
+ #wal_add_optimization_info = off	# write logical log correspond to full
+ 					# page.
  #wal_buffers = 64kB			# min 32kB
  					# (change requires restart)
  #commit_delay = 0			# range 0-100000, in microseconds
diff -Ncar postgresql-8.2.1.org/src/include/access/xlog.h postgresql-8.2.1/src/include/access/xlog.h
*** postgresql-8.2.1.org/src/include/access/xlog.h	2006-11-06 07:42:10.000000000 +0900
--- postgresql-8.2.1/src/include/access/xlog.h	2007-04-06 16:54:23.000000000 +0900
***************
*** 66,73 ****
  /*
   * If we backed up any disk blocks with the XLOG record, we use flag bits in
   * xl_info to signal it.  We support backup of up to 3 disk blocks per XLOG
!  * record.	(Could support 4 if we cared to dedicate all the xl_info bits for
!  * this purpose; currently bit 0 of xl_info is unused and available.)
   */
  #define XLR_BKP_BLOCK_MASK		0x0E	/* all info bits used for bkp blocks */
  #define XLR_MAX_BKP_BLOCKS		3
--- 66,74 ----
  /*
   * If we backed up any disk blocks with the XLOG record, we use flag bits in
   * xl_info to signal it.  We support backup of up to 3 disk blocks per XLOG
!  * record.
!  * Bit 0 of xl_info is used to represent that backup blocks are not necessary
!  * in archive-log.
   */
  #define XLR_BKP_BLOCK_MASK		0x0E	/* all info bits used for bkp blocks */
  #define XLR_MAX_BKP_BLOCKS		3
***************
*** 75,80 ****
--- 76,82 ----
  #define XLR_BKP_BLOCK_1			XLR_SET_BKP_BLOCK(0)	/* 0x08 */
  #define XLR_BKP_BLOCK_2			XLR_SET_BKP_BLOCK(1)	/* 0x04 */
  #define XLR_BKP_BLOCK_3			XLR_SET_BKP_BLOCK(2)	/* 0x02 */
+ #define XLR_BKP_REMOVABLE		XLR_SET_BKP_BLOCK(3)	/* 0x01 */
  
  /*
   * Sometimes we log records which are out of transaction control.