diff --git a/bin/rrd-extractstats.pl b/bin/rrd-extractstats.pl
index 9a824ab..0384ce1 100755
--- a/bin/rrd-extractstats.pl
+++ b/bin/rrd-extractstats.pl
@@ -10,11 +10,17 @@ use warnings;
 use RRDs;
 use File::Find;
 use File::Find::Rule;
+use DBI;
+use TryCatch;
+use File::Copy qw(copy);
+use File::stat;
 
 use threads       ;#qw( async );
 use threads::shared;
 use Thread::Queue qw( );
 
+use Time::HiRes qw(time);
+
 if ($#ARGV < 2) {
 	die("Usage: $0 <path to RRD file directory> <path to known links file> outfile [interval-hours]\n");
 }
@@ -34,47 +40,84 @@ read_knownlinks();
 
 my @links = values %knownlinks;
 
+# If the DB has it, get latest check timestamp for every ASN we are aware of
+my $db_version = 1;
+my $as_list;
+my $db;
+try {
+	if (-r $statsfile) { 
+		copy($statsfile, "$statsfile.tmp");
+	}
+	$db = DBI->connect("dbi:SQLite:dbname=$statsfile.tmp", '', '');
+
+	# Get last check timestamps
+	my $sth = $db->prepare("SELECT asn, checked_at FROM stats") or die('field missing');
+	$sth->execute();
+	while(my($item, $data) = $sth->fetchrow_array()) {
+		as_list->{$item} = $data;
+	}
+
+	$db_version = 2;
+} catch ($e) {
+	print("Previously generated database not found or checked_at field is missing, proceed with all RRD files. ($e)\n");
+}
+
 # walk through all RRD files in the given path and extract stats for all links
 # from them; write the stats to an sqlite database
 
-my @rrdfiles = File::Find::Rule->maxdepth(2)->file->in($rrdpath);
+my @rrdfiles = File::Find::Rule->maxdepth(2)->file()->name('*.rrd')->in($rrdpath);
 
 $|=1;
-my $i :shared = 0;
 
 my $num_workers	= 1;
 if (($ENV{'THREADS'} =~ /^\d+$/) and ($ENV{'THREADS'} > 0)) { 
     $num_workers = $ENV{'THREADS'};
 }
-print("Using " . $num_workers . " threads.\n");
 
 my $num_work_units = scalar @rrdfiles;
 
+print("Using " . $num_workers . " threads to process " . $num_work_units . " RRD files.\n");
+
 my $q = Thread::Queue->new();
 my $rq = Thread::Queue->new();
 
 # Create work
 foreach my $rrdfile (@rrdfiles) {
 	if ($rrdfile =~ /\/(\d+).rrd$/) {
-		my $as = $1;
-		$q->enqueue($as);
+		my $task->{as} = $1;
+		$task->{filename} = $rrdfile;
+		$q->enqueue($task);
 	}
 }
 
+my $i :shared = 0;
+my $skipped :shared = 0;
+my $t :shared = scalar time;
+my $t0 :shared = scalar time;
+
 # Create workers
 my @workers;
 for (1..$num_workers) {
 	push @workers, async {
-		while (defined(my $as = $q->dequeue())) {
-			my $result->{as} = $as;
-			$result->{result} = gettraffic($as, time - $interval, time);
+		while (defined(my $task = $q->dequeue())) {
+			if ($as_list->{$task->{as}} and (!(stat($task->{filename})->mtime > $as_list->{$task->{as}}))) {
+				$skipped += 1;
+			} else {
+				my $result->{as} = $task->{as};
+				$result->{checked_at} = int time;
+				$result->{result} = gettraffic($task->{as}, int time - $interval, int time);
 
-			# Put result to result queue
-			$rq->enqueue($result);
+				# Put result to result queue
+				$rq->enqueue($result);
+			}
 
 			$i++;
 			if ($i % 100 == 0) {
-				print int($i / $num_work_units * 100 * 100) / 100 . "%... ";
+				my $average_speed = int(($i / (scalar time - $t0)) * 100) / 100;
+				my $current_speed = int((100 / (scalar time - $t)) * 100) / 100;
+				my $seconds_left = ($num_work_units - $i) / $average_speed;
+				printf("%.2f%% (files per sec cur/avg %.2f/%.2f, proc/skip/total %d/%d/%d, %02d:%02d:%02d left)\n", int($i / $num_work_units * 100 * 100) / 100, $current_speed, $average_speed, ($i - $skipped), $skipped, $num_work_units, $seconds_left / 3600, $seconds_left / 60 % 60, $seconds_left % 60);
+				$t = scalar time;
 			}
 		}
 	};
@@ -86,26 +129,28 @@ $q->enqueue(undef) for @workers;
 # Wait for workers to end
 $_->join() for @workers;
 
-print "100%";
+printf("100%% (processed %d RRD files, skipped %d because those files didn't change since last run)\n", $num_work_units - $skipped, $skipped);
 
 $rq->end();
 
-my $query = 'create table stats("asn" int';
-foreach my $link (@links) {
-	$query .= ", \"${link}_in\" int, \"${link}_out\" int, \"${link}_v6_in\" int, \"${link}_v6_out\" int";
-}
-$query .= ');';
 
-use DBI;
-my $db = DBI->connect("dbi:SQLite:dbname=$statsfile.tmp", '', '');
 $db->do('PRAGMA synchronous = OFF');
-$db->do('drop table if exists stats');
-$db->do($query);
+my $query;
+# Recreate the table if we didn't have the checked_at column above
+if ($db_version < 2) {
+	$db->do('DROP TABLE IF EXISTS stats;');
+	
+	$query = 'CREATE TABLE stats("asn" INT PRIMARY KEY, "checked_at" INT';
+	foreach my $link (@links) {
+		$query .= ", \"${link}_in\" INT, \"${link}_out\" INT, \"${link}_v6_in\" INT, \"${link}_v6_out\" INT";
+	}
+	$query .= ');';
+	$db->do($query);
+}
 
 # read resultqueue and print data
 while (my $result = $rq->dequeue) {
-	my $as = $result->{as};
-	$query = "insert into stats values('$as'";
+	$query = "INSERT OR REPLACE INTO stats VALUES ($result->{as}, $result->{checked_at}";
 
 	foreach my $link (@links) {
 		$query .= ", '" . undefaszero($result->{result}->{"${link}_in"}) . "'";