nntp: make XOVER, XHDR, OVER, HDR and NEWNEWS faster

While SQLite is faster than Xapian for some queries we
use, it sucks at handling OFFSET.  Fortunately, we do
not need offsets when retrieving sorted results and
can bake it into the query.

For inbox.comp.version-control.git (v1 Xapian),
XOVER and XHDR are over 20x faster.

1 files changed, 8 insertions, 7 deletions

diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index 3d285ac2..a7fd1315 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -51,25 +51,26 @@ sub do_get {
         my $dbh = $self->connect;
         my $lim = (($opts->{limit} || 0) + 0) || 1000;
         my $off = (($opts->{offset} || 0) + 0) || 0;
-        $sql .= "LIMIT $lim OFFSET $off";
+        $sql .= "LIMIT $lim";
+        $sql .= " OFFSET $off" if $off > 0;
         my $msgs = $dbh->selectall_arrayref($sql, { Slice => {} }, @args);
         load_from_row($_) for @$msgs;
         $msgs
 }
 
 sub query_xover {
-        my ($self, $beg, $end, $off) = @_;
-        do_get($self, <<'', { offset => $off }, $beg, $end);
+        my ($self, $beg, $end) = @_;
+        do_get($self, <<'', {}, $beg, $end);
 SELECT * FROM over WHERE num >= ? AND num <= ?
 ORDER BY num ASC
 
 }
 
 sub query_ts {
-        my ($self, $ts, $opts) = @_;
-        do_get($self, <<'', $opts, $ts);
-SELECT * FROM over WHERE num > 0 AND ts >= ?
-ORDER BY ts ASC
+        my ($self, $ts, $prev) = @_;
+        do_get($self, <<'', {}, $ts, $prev);
+SELECT num,ddd FROM over WHERE ts >= ? AND num > ?
+ORDER BY num ASC
 
 }