--- loncom/debugging_tools/rebuild_db_from_hist.pl	2006/08/03 17:53:47	1.6
+++ loncom/debugging_tools/rebuild_db_from_hist.pl	2016/01/31 21:26:01	1.7
@@ -4,7 +4,7 @@
 #
 # rebuild_db_from_hist.pl Rebuild a *.db file from a *.hist file
 #
-# $Id: rebuild_db_from_hist.pl,v 1.6 2006/08/03 17:53:47 albertel Exp $
+# $Id: rebuild_db_from_hist.pl,v 1.7 2016/01/31 21:26:01 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -125,13 +125,14 @@ sub process_file {
         #  D:delete
         #  N:new put (only adds tha values if they are all new values)
 	#  M:modify the values for a previous S
+        #  U:update the values (action could be add or del).
         my ($action,$time,$concatenated_data) = split(':',$command,3);
         if ($fname eq 'roles.hist' && $concatenated_data =~ /^.*:.*:/) {
             (undef,undef,$concatenated_data) = split(':',$concatenated_data,3);
         }
         next if (! defined($action));
         if ($action eq 'P' && $p_is_s) { $action = 'S'; }
-        my ($rid,@allkeys,$version);
+        my ($rid,@allkeys,$version,$updatetype);
         if ($action eq 'S') {
             ($rid,$concatenated_data) = split(':',$concatenated_data,2);
             $version = ++$db_to_store{"version:$rid"};
@@ -141,6 +142,10 @@ sub process_file {
             ($rid,$version,$concatenated_data) = 
 		split(':',$concatenated_data,3);
 	}
+        if ($action eq 'U') {
+            ($updatetype,$concatenated_data) =
+                split(':',$concatenated_data,2); 
+        }
         next if (! defined($concatenated_data));
 	my $add_new_data = 1;
         my @data = split('&',$concatenated_data);
@@ -163,6 +168,28 @@ sub process_file {
 		}
             } elsif ($action eq 'D') {
                 delete($db_to_store{$key});
+            } elsif ($action eq 'U') {
+                if ($updatetype eq 'del') {
+                    if (exists($db_to_store{$key})) {
+                        my %current;
+                        map { $current{$_} = 1; } split(/,/,&unescape($db_to_store{$key}));
+                        map { delete($current{$_}); } split(/,/,&unescape($value));
+                        if (keys(%current)) {
+                            $db_to_store{$key}=&escape(join(',',sort(keys(%current))));
+                        } else {
+                            delete($db_to_store{$key});
+                        }
+                    }
+                } elsif ($updatetype eq 'add') {
+                    if (exists($db_to_store{$key})) {
+                        my @newvals = split(/,/,&unescape($value));
+                        my @currvals = split(/,/,&unescape($db_to_store{$key}));
+                        my @merged = sort(keys(%{{map { $_ => 1 } (@newvals,@currvals)}}));
+                        $db_to_store{$key}=&escape(join(',',@merged));
+                    } else {
+                        $db_to_store{$key}=$value;
+                    }
+                }
             } else {
                 $error = "Unable to understand action '".$action."'";
             }