Index: backend/postmaster/pgstat.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/postmaster/pgstat.c,v
retrieving revision 1.179
diff -c -r1.179 pgstat.c
*** backend/postmaster/pgstat.c	15 Aug 2008 08:37:39 -0000	1.179
--- backend/postmaster/pgstat.c	19 Aug 2008 15:24:59 -0000
***************
*** 110,115 ****
--- 110,116 ----
   */
  char	   *pgstat_stat_filename = NULL;
  char	   *pgstat_stat_tmpname = NULL;
+ char	   *pgstat_stat_lastname = NULL;
  
  /*
   * BgWriter global statistics counters (unused in other processes).
***************
*** 203,208 ****
--- 204,210 ----
  
  static volatile bool need_exit = false;
  static volatile bool need_statwrite = false;
+ static volatile bool got_SIGHUP = false;
  
  /*
   * Total time charged to functions so far in the current backend.
***************
*** 224,229 ****
--- 226,232 ----
  static void pgstat_exit(SIGNAL_ARGS);
  static void force_statwrite(SIGNAL_ARGS);
  static void pgstat_beshutdown_hook(int code, Datum arg);
+ static void pgstat_sighup_handler(SIGNAL_ARGS);
  
  static PgStat_StatDBEntry *pgstat_get_db_entry(Oid databaseid, bool create);
  static void pgstat_write_statsfile(bool permanent);
***************
*** 2571,2577 ****
  	 * Ignore all signals usually bound to some action in the postmaster,
  	 * except SIGQUIT and SIGALRM.
  	 */
! 	pqsignal(SIGHUP, SIG_IGN);
  	pqsignal(SIGINT, SIG_IGN);
  	pqsignal(SIGTERM, SIG_IGN);
  	pqsignal(SIGQUIT, pgstat_exit);
--- 2574,2580 ----
  	 * Ignore all signals usually bound to some action in the postmaster,
  	 * except SIGQUIT and SIGALRM.
  	 */
! 	pqsignal(SIGHUP, pgstat_sighup_handler);
  	pqsignal(SIGINT, SIG_IGN);
  	pqsignal(SIGTERM, SIG_IGN);
  	pqsignal(SIGQUIT, pgstat_exit);
***************
*** 2635,2640 ****
--- 2638,2652 ----
  			break;
  
  		/*
+ 		 * Reload configuration if we got SIGHUP from the postmaster.
+ 		 */
+ 		if (got_SIGHUP)
+ 		{
+ 			ProcessConfigFile(PGC_SIGHUP);
+ 			got_SIGHUP = false;
+ 		}
+ 
+ 		/*
  		 * If time to write the stats file, do so.	Note that the alarm
  		 * interrupt isn't re-enabled immediately, but only after we next
  		 * receive a stats message; so no cycles are wasted when there is
***************
*** 2834,2839 ****
--- 2846,2858 ----
  	need_statwrite = true;
  }
  
+ /* SIGHUP handler for collector process */
+ static void
+ pgstat_sighup_handler(SIGNAL_ARGS)
+ {
+ 	got_SIGHUP = true;
+ }
+ 
  
  /*
   * Lookup the hash table entry for the specified database. If no hash
***************
*** 3018,3023 ****
--- 3037,3059 ----
  
  	if (permanent)
  		unlink(pgstat_stat_filename);
+ 	else
+ 	{
+ 		/*
+ 		 * If the old filename exists, we need to unlink it now that we have written
+ 		 * the new file. This indicates that we are done, and it also makes it possible
+ 		 * to switch the directory back without getting the old data.
+ 		 *
+ 		 * Also do away with the old name here, so we don't try to delete it again.
+ 		 */
+ 		if (pgstat_stat_lastname != NULL)
+ 		{
+ 			unlink(pgstat_stat_lastname);
+ 
+ 			free(pgstat_stat_lastname);
+ 			pgstat_stat_lastname = NULL;
+ 		}
+ 	}
  }
  
  
***************
*** 3072,3080 ****
  	 * Try to open the status file. If it doesn't exist, the backends simply
  	 * return zero for anything and the collector simply starts from scratch
  	 * with empty counters.
  	 */
  	if ((fpin = AllocateFile(statfile, PG_BINARY_R)) == NULL)
! 		return dbhash;
  
  	/*
  	 * Verify it's of the expected format.
--- 3108,3128 ----
  	 * Try to open the status file. If it doesn't exist, the backends simply
  	 * return zero for anything and the collector simply starts from scratch
  	 * with empty counters.
+ 	 * If we are loading the temporary file, look at pgstat_stat_lastname as
+ 	 * well, in case the filename changed recently and the collector hasn't
+ 	 * written the new file yet.
  	 */
  	if ((fpin = AllocateFile(statfile, PG_BINARY_R)) == NULL)
! 	{
! 		if (!permanent && pgstat_stat_lastname != NULL)
! 		{
! 			/* attempt to load the old file if it's there */
! 			if ((fpin = AllocateFile(pgstat_stat_lastname, PG_BINARY_R)) == NULL)
! 				return dbhash;
! 		}
! 		else 
! 			return dbhash;
! 	}
  
  	/*
  	 * Verify it's of the expected format.
Index: backend/postmaster/postmaster.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v
retrieving revision 1.561
diff -c -r1.561 postmaster.c
*** backend/postmaster/postmaster.c	26 Jun 2008 02:47:19 -0000	1.561
--- backend/postmaster/postmaster.c	19 Aug 2008 15:24:59 -0000
***************
*** 1923,1932 ****
  			signal_child(PgArchPID, SIGHUP);
  		if (SysLoggerPID != 0)
  			signal_child(SysLoggerPID, SIGHUP);
! 		/* PgStatPID does not currently need SIGHUP */
  
  		/* Reload authentication config files too */
  		load_ident();
  
  #ifdef EXEC_BACKEND
--- 1931,1944 ----
  			signal_child(PgArchPID, SIGHUP);
  		if (SysLoggerPID != 0)
  			signal_child(SysLoggerPID, SIGHUP);
! 		if (PgStatPID != 0)
! 			signal_child(PgStatPID, SIGHUP);
  
  		/* Reload authentication config files too */
  		load_ident();
  
  #ifdef EXEC_BACKEND
Index: backend/utils/misc/guc.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v
retrieving revision 1.466
diff -c -r1.466 guc.c
*** backend/utils/misc/guc.c	15 Aug 2008 08:37:40 -0000	1.466
--- backend/utils/misc/guc.c	19 Aug 2008 15:24:59 -0000
***************
*** 2470,2476 ****
  	},
  
  	{
! 		{"stats_temp_directory", PGC_POSTMASTER, STATS_COLLECTOR,
  			gettext_noop("Writes temporary statistics files to the specified directory."),
  			NULL,
  			GUC_SUPERUSER_ONLY
--- 2470,2476 ----
  	},
  
  	{
! 		{"stats_temp_directory", PGC_SIGHUP, STATS_COLLECTOR,
  			gettext_noop("Writes temporary statistics files to the specified directory."),
  			NULL,
  			GUC_SUPERUSER_ONLY
***************
*** 7390,7397 ****
  	{
  		if (pgstat_stat_tmpname)
  			free(pgstat_stat_tmpname);
  		if (pgstat_stat_filename)
! 			free(pgstat_stat_filename);
  
  		pgstat_stat_tmpname = guc_malloc(FATAL, strlen(newval) + 12);  /* /pgstat.tmp */
  		pgstat_stat_filename = guc_malloc(FATAL, strlen(newval) + 13); /* /pgstat.stat */
--- 7390,7404 ----
  	{
  		if (pgstat_stat_tmpname)
  			free(pgstat_stat_tmpname);
+ 
+ 		/* save away the last filename used */
  		if (pgstat_stat_filename)
! 		{
! 			if (pgstat_stat_lastname)
! 				free(pgstat_stat_lastname);
! 
! 			pgstat_stat_lastname = pgstat_stat_filename;
! 		}
  
  		pgstat_stat_tmpname = guc_malloc(FATAL, strlen(newval) + 12);  /* /pgstat.tmp */
  		pgstat_stat_filename = guc_malloc(FATAL, strlen(newval) + 13); /* /pgstat.stat */
Index: include/pgstat.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/pgstat.h,v
retrieving revision 1.78
diff -c -r1.78 pgstat.h
*** include/pgstat.h	15 Aug 2008 08:37:40 -0000	1.78
--- include/pgstat.h	19 Aug 2008 15:24:59 -0000
***************
*** 578,583 ****
--- 578,584 ----
  extern int	pgstat_track_activity_query_size;
  extern char *pgstat_stat_tmpname;
  extern char *pgstat_stat_filename;
+ extern char *pgstat_stat_lastname;
  
  /*
   * BgWriter statistics counters are updated directly by bgwriter and bufmgr