lib/PublicInbox/Search.pm    | 1 +
 lib/PublicInbox/SearchIdx.pm | 1 +
 t/search.t                   | 5 +++++

diff --git a/lib/PublicInbox/Search.pm b/lib/PublicInbox/Search.pm
index f2d3b92dc821e87e71b5dd2cc3f7729157f02494..c54cf7b9911affce9680e7160b1fdecbb3aad20f 100644
--- a/lib/PublicInbox/Search.pm
+++ b/lib/PublicInbox/Search.pm
@@ -12,6 +12,7 @@ 	TS => 0, # Received: header in Unix time (IMAP INTERNALDATE)
 	YYYYMMDD => 1, # Date: header for searching in the WWW UI
 	DT => 2, # Date: YYYYMMDDHHMMSS
 	BYTES => 3, # IMAP RFC822.SIZE
+	UID => 4, # IMAP UID == NNTP article number == Xapian docid
 	# TODO
 	# REPLYCNT => 4, # IMAP ANSWERED
 };
diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index f7462aa74ca0aa7ff73992437ffeca36c65e60ca..3df7970ebf984252f006056042946425e8ef7335 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -342,6 +342,7 @@ 	add_val($doc, PublicInbox::Search::YYYYMMDD(), $yyyymmdd);
 	my $dt = strftime('%Y%m%d%H%M%S', @ds);
 	add_val($doc, PublicInbox::Search::DT(), $dt);
 	add_val($doc, PublicInbox::Search::BYTES(), $smsg->{bytes});
+	add_val($doc, PublicInbox::Search::UID(), $smsg->{num});
 
 	my $tg = term_generator($self);
 	$tg->set_document($doc);
diff --git a/t/search.t b/t/search.t
index cf3254169ca3485e689e5498f97df82b2b0dc69f..d4ca28c794f8255b648100355c40726c3e3e88c5 100644
--- a/t/search.t
+++ b/t/search.t
@@ -324,6 +324,11 @@ 		my $bytes = PublicInbox::Smsg::get_val($doc, $col);
 		like($bytes, qr/\A[0-9]+\z/, '$bytes stored as digit');
 		ok($bytes > 0, '$bytes is > 0');
 		is($bytes, $smsg->{bytes}, 'bytes Xapian value matches Over');
+
+		$col = PublicInbox::Search::UID();
+		my $uid = PublicInbox::Smsg::get_val($doc, $col);
+		is($uid, $smsg->{num}, 'UID column matches {num}');
+		is($uid, $m->get_docid, 'UID column matches docid');
 	}
 
 	$mset = $ro->query('tc:list@example.com', {mset => 1});