searchidx: use add_boolean_term for internal terms

Aside from the Message-Id ('Q'), these terms do not appear in
content and thus have no business contributing to the Xapian
document length.

Thanks-to Olly Betts for the tip on xapian-discuss
<20180228004400.GU12724@survex.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/PublicInbox/SearchMsg.pm b/lib/PublicInbox/SearchMsg.pm
index a5565345..93e6fd8b 100644
--- a/lib/PublicInbox/SearchMsg.pm
+++ b/lib/PublicInbox/SearchMsg.pm
@@ -14,7 +14,7 @@ use PublicInbox::Address;
 sub new {
         my ($class, $mime) = @_;
         my $doc = Search::Xapian::Document->new;
-        $doc->add_term('T' . 'mail');
+        $doc->add_boolean_term('T' . 'mail');
 
         bless { type => 'mail', doc => $doc, mime => $mime }, $class;
 }