lei: avoid SQLite COUNT() for dedupe

SQLite COUNT() is a slow operation that does a full table scan
with no conditions.  There's no need for it, since lei dedupe
only needs to know if it's empty or not to decide between
new/ and cur/ for Maildir outputs.

1 files changed, 4 insertions, 4 deletions

diff --git a/lib/PublicInbox/LeiSavedSearch.pm b/lib/PublicInbox/LeiSavedSearch.pm
index 929380ed..cfbf68c3 100644
--- a/lib/PublicInbox/LeiSavedSearch.pm
+++ b/lib/PublicInbox/LeiSavedSearch.pm
@@ -315,11 +315,11 @@ E: rename($dir_old, $dir_new) error: $!
 EOM
 }
 
-# cf. LeiDedupe->dedupe_nr
-sub dedupe_nr {
+# cf. LeiDedupe->has_entries
+sub has_entries {
         my $oidx = $_[0]->{oidx} // die 'BUG: no {oidx}';
-        my @n = $oidx->{dbh}->selectrow_array('SELECT COUNT(*) FROM over');
-        $n[0];
+        my @n = $oidx->{dbh}->selectrow_array('SELECT num FROM over LIMIT 1');
+        scalar(@n) ? 1 : undef;
 }
 
 no warnings 'once';