imap: EXAMINE: avoid potential race conditions

We need to rely on num_highwater for UIDNEXT since the
highest `num' stored in over.sqlite3 may be rolled back
if the most recent messages were spam.

We also need to load the uo2m immediately on EXAMINE to ensure
EXISTS responses are always consistent with regard to future
updates.

1 files changed, 3 insertions, 15 deletions

diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index 74c8fb86..e5a980d5 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -248,25 +248,13 @@ SELECT MAX(num) FROM over WHERE num > 0
         $sth->fetchrow_array // 0;
 }
 
-sub imap_status {
+sub imap_exists {
         my ($self, $uid_base, $uid_end) = @_;
-        my $dbh = $self->connect;
-        my $sth = $dbh->prepare_cached(<<'', undef, 1);
+        my $sth = $self->connect->prepare_cached(<<'', undef, 1);
 SELECT COUNT(num) FROM over WHERE num > ? AND num <= ?
 
         $sth->execute($uid_base, $uid_end);
-        my $exists = $sth->fetchrow_array;
-
-        $sth = $dbh->prepare_cached(<<'', undef, 1);
-SELECT MAX(num) + 1 FROM over WHERE num <= ?
-
-        $sth->execute($uid_end);
-        my $uidnext = $sth->fetchrow_array;
-
-        $sth = $dbh->prepare_cached(<<'', undef, 1);
-SELECT MAX(num) FROM over WHERE num > 0
-
-        ($exists, $uidnext, $sth->fetchrow_array // 0);
+        $sth->fetchrow_array;
 }
 
 sub check_inodes {