Add a last_activity field to user_stats table, and set that from libdb

where we insert the testbed_stats record. This will make it much much faster
to generate the recent users list in genelists (currently taking 3 seconds!).

db/libdb.pm.in

@@ -4711,6 +4711,7 @@ sub GatherSwapStats($$$$$;$)
 		" action, exitcode) ".
 		"values (0, '$uid', $starttime, now(), $exptidx, $rsrcidx, ".
 		"        '$mode', $ecode)");
+    DBQueryWarn("update user_stats set last_activity=now() where uid='$uid'");
 }
 
 #

sql/database-create.sql

@@ -1855,6 +1855,7 @@ CREATE TABLE user_stats (
   exptswapout_last datetime default NULL,
   exptswapmod_count int(11) unsigned default '0',
   exptswapmod_last datetime default NULL,
+  last_activity datetime default NULL,
   allexpt_duration int(11) unsigned default '0',
   allexpt_vnodes int(11) unsigned default '0',
   allexpt_vnode_duration int(11) unsigned default '0',

sql/database-migrate.txt

@@ -2726,3 +2726,20 @@ last_net_act,last_cpu_act,last_ext_act);
 	  created datetime default NULL,
 	  PRIMARY KEY  (listname)
 	) TYPE=MyISAM;
+
+4.3: Add a last_activity field to user_stats to make it easier to
+     determine recent users (in genelists).
+
+	alter table user_stats add last_activity datetime \
+               default NULL after exptswapmod_last;
+
+      To seed this table:
+
+	update user_stats set last_activity =
+	    FROM_UNIXTIME(GREATEST(UNIX_TIMESTAMP(exptstart_last),
+	                           UNIX_TIMESTAMP(exptpreload_last),
+                                   UNIX_TIMESTAMP(exptswapin_last),
+                                   UNIX_TIMESTAMP(exptswapout_last),
+                                   UNIX_TIMESTAMP(exptswapmod_last)));
+
+4.4: