diff --git a/db/libdb.pm.in b/db/libdb.pm.in
index 21152bbd951eacf4af59a52031184b1f6880a6da..c713de17041f39abc7dc5657ab52a81de693168d 100644
--- a/db/libdb.pm.in
+++ b/db/libdb.pm.in
@@ -3252,8 +3252,8 @@ sub GatherSwapStats($$$$$;$)
 	$flags & TBDB_STATS_FLAGS_PREMODIFY) {
 	$query_result = 
 	    DBQueryWarn("insert into experiment_resources ".
-			" (idx, tstamp, exptidx) ".
-			"values (0, now(), $exptidx)");
+			" (idx, tstamp, exptidx, lastidx) ".
+			"values (0, now(), $exptidx, $rsrcidx)");
 	if (! $query_result ||
 	    ! $query_result->insertid) {
 	    print STDERR
diff --git a/sql/database-create.sql b/sql/database-create.sql
index 74f2094da588082ec97c66f21d3f0cab0fdad278..96c028e5ae03d3a483934f7eb2c4e12c26dcc6c0 100644
--- a/sql/database-create.sql
+++ b/sql/database-create.sql
@@ -172,6 +172,7 @@ CREATE TABLE eventlist (
 CREATE TABLE experiment_resources (
   idx int(10) unsigned NOT NULL auto_increment,
   exptidx int(10) unsigned NOT NULL default '0',
+  lastidx int(10) unsigned default NULL,
   tstamp datetime default NULL,
   vnodes smallint(5) unsigned default '0',
   pnodes smallint(5) unsigned default '0',
@@ -188,7 +189,8 @@ CREATE TABLE experiment_resources (
   minlinks tinyint(3) unsigned default '0',
   maxlinks tinyint(3) unsigned default '0',
   PRIMARY KEY  (idx),
-  KEY exptidx (exptidx)
+  KEY exptidx (exptidx),
+  KEY lastidx (lastidx)
 ) TYPE=MyISAM;
 
 --
diff --git a/sql/database-migrate.txt b/sql/database-migrate.txt
index 7eb2a9fd6337304d7965014eb4a0feaf9388b332..5e749b25d686437b09b36a6779bd95df16a8c292 100644
--- a/sql/database-migrate.txt
+++ b/sql/database-migrate.txt
@@ -693,3 +693,31 @@ last_net_act,last_cpu_act,last_ext_act);
 	alter ignore table comments modify 
 		column_name varchar(64) not null default "";
 
+1.158: Add chain field to experiment_resources to make it easier to
+       step back through experiment history, and keep the join size
+       down.
+
+        alter table experiment_resources add lastidx int(10)
+			unsigned default NULL after exptidx;
+	alter table experiment_resources add index(lastidx);
+
+	my $query_result =
+	    DBQueryWarn("select idx,exptidx from experiment_resources ".
+			"order by exptidx,tstamp asc");
+
+	my $lastexpt = -1;
+	my $lastidx  = -1;
+
+	while (($idx,$exptidx) = $query_result->fetchrow_array()) {
+	    if ($exptidx != $lastexpt) {
+		print "update experiment_resources set lastidx=NULL ".
+		    "where exptidx=$exptidx and idx=$idx;\n";
+		$lastexpt = $exptidx;
+		$lastidx  = $idx;
+		next;
+	    }
+	    print "update experiment_resources set lastidx=$lastidx ".
+		"where exptidx=$exptidx and idx=$idx;\n";
+	    $lastidx  = $idx;
+	}
+	
\ No newline at end of file
diff --git a/www/showsumstats.php3 b/www/showsumstats.php3
index b09cadff4bc9dcedb16e8a959eb8696701e67dc1..e8b56427b03375ac40b27d7b745c194d7019e181 100644
--- a/www/showsumstats.php3
+++ b/www/showsumstats.php3
@@ -238,7 +238,7 @@ function edaycmp ($a, $b) {
 
 function showrange ($showby, $sortby, $range) {
     global $TBOPSPID, $TB_EXPTSTATE_ACTIVE;
-    $debug = 0;
+    $debug = 1;
     
     switch ($range) {
         case "day":
@@ -328,7 +328,7 @@ function showrange ($showby, $sortby, $range) {
 		     "left join experiment_resources as r1 on ".
 		     "  r1.idx=t.rsrcidx ".
 		     "left join experiment_resources as r2 on ".
-		     "  r2.idx=s.lastrsrc and s.lastrsrc is not null ".
+		     "  r2.idx=r1.lastidx and r1.lastidx is not null ".
 		     "where t.exitcode = 0 && ".
 		     "    ((UNIX_TIMESTAMP(now())-UNIX_TIMESTAMP(t.tstamp)) ".
 		     "     < $wclause) ".
@@ -393,7 +393,7 @@ function showrange ($showby, $sortby, $range) {
 	}
 
 	if ($debug) 
-	    echo "$idx $pid $eid $uid $tstamp $action $pnodes<br>\n";
+	    echo "$idx $pid $eid $uid $tstamp $action $pnodes $pnodes2<br>\n";
 
 	switch ($action) {
         case "start":
@@ -440,11 +440,10 @@ function showrange ($showby, $sortby, $range) {
 	    # Basically, start the clock ticking again with the new
 	    # number of pnodes.
 	    if ($action == "swapmod") {
-		# Yuck, we redefined uid above, but we want to start the
-		# new record for the current swapper.
-		$uid = $row["uid"];
-		$expt_start["$pid:$eid"] = array('pnodes' => $pnodes,
-						 'uid'    => $uid,
+		# Yuck, we redefined uid/pnodes above, but we want to start the
+		# new record for the current swapper/#pnodes.
+		$expt_start["$pid:$eid"] = array('pnodes' => $row['pnodes1'],
+						 'uid'    => $row['uid'],
 						 'pid'    => $pid,
 						 'stamp'  => $tstamp);
 	    }