imap: STATUS/EXAMINE: rely on SQLite overview

We can get exact values for EXISTS, UIDNEXT using SQLite
rather than calculating off $ibx->mm->max ourselves.

Furthermore, $ibx->mm is less useful than $ibx->over for IMAP
(and for our read-only daemons in general) so do not depend on
$ibx->mm outside of startup/reload to save FDs and reduce kernel
page cache footprint.

5 files changed, 58 insertions, 18 deletions

diff --git a/lib/PublicInbox/DummyInbox.pm b/lib/PublicInbox/DummyInbox.pm
index b6c48db1..c3f4f5c6 100644
--- a/lib/PublicInbox/DummyInbox.pm
+++ b/lib/PublicInbox/DummyInbox.pm
@@ -9,13 +9,14 @@ use strict;
 
 sub created_at { 0 } # Msgmap::created_at
 sub mm { shift }
-sub max { undef } # Msgmap::max
-sub msg_range { [] } # Msgmap::msg_range
+sub uid_range { [] } # Over::uid_range
+sub subscribe_unlock { undef };
 
 no warnings 'once';
-*uid_range = *query_xover = \&msg_range;
+*max = \&created_at;
+*query_xover = \&uid_range;
 *over = \&mm;
-*subscribe_unlock = *unsubscribe_unlock =
-        *get_art = *description = *base_url = \&max;
+*unsubscribe_unlock =
+        *get_art = *description = *base_url = \&subscribe_unlock;
 
 1;
diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index d0683530..41c80664 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -183,7 +183,7 @@ sub cmd_noop ($$) { "$_[1] OK Noop done\r\n" }
 # called by PublicInbox::InboxIdle
 sub on_inbox_unlock {
         my ($self, $ibx) = @_;
-        my $new = $ibx->mm->max;
+        my $new = $ibx->over->max;
         my $uid_base = $self->{uid_base} // 0;
         my $uid_end = $uid_base + UID_BLOCK;
         defined(my $old = $self->{-idle_max}) or die 'BUG: -idle_max unset';
@@ -223,7 +223,7 @@ sub cmd_idle ($$) {
         # IDLE seems allowed by dovecot w/o a mailbox selected *shrug*
         my $ibx = $self->{ibx} or return "$tag BAD no mailbox selected\r\n";
         $self->{-idle_tag} = $tag;
-        my $max = $ibx->mm->max // 0;
+        my $max = $ibx->over->max;
         my $uid_end = $self->{uid_base} + UID_BLOCK;
         my $sock = $self->{sock} or return;
         my $fd = fileno($sock);
@@ -283,14 +283,20 @@ sub inbox_lookup ($$) {
                 my $mb_top = $1;
                 $uid_base = $2 * UID_BLOCK;
                 $ibx = $self->{imapd}->{mailboxes}->{lc $mailbox} or return;
-                $exists = $ibx->mm->max // 0;
-                ensure_ranges_exist($self->{imapd}, $ibx, $exists);
-                my $uid_end = $uid_base + UID_BLOCK;
-                $exists = $uid_end if $exists > $uid_end;
-                $uidnext = $exists + 1;
-                $exists -= $uid_base;
+                my $max;
+                ($exists, $uidnext, $max) = $ibx->over->imap_status($uid_base,
+                                                        $uid_base + UID_BLOCK);
+                ensure_ranges_exist($self->{imapd}, $ibx, $max);
         } else { # check for dummy inboxes
-                $ibx = $self->{imapd}->{mailboxes}->{lc $mailbox} or return;
+                $mailbox = lc $mailbox;
+                $ibx = $self->{imapd}->{mailboxes}->{$mailbox} or return;
+
+                # if "INBOX.foo.bar" is selected and "INBOX.foo.bar.0",
+                # check for new UID ranges (e.g. "INBOX.foo.bar.1")
+                if (my $z = $self->{imapd}->{mailboxes}->{"$mailbox.0"}) {
+                        ensure_ranges_exist($self->{imapd}, $z, $z->over->max);
+                }
+
                 $uid_base = $exists = 0;
                 $uidnext = 1;
         }
@@ -590,7 +596,7 @@ sub range_step ($$) {
                 ($beg, $end) = ($1 + 0, $2 + 0);
         } elsif ($range =~ /\A([0-9]+):\*\z/) {
                 $beg = $1 + 0;
-                $end = $self->{ibx}->mm->max // 0;
+                $end = $self->{ibx}->over->max;
                 my $uid_end = $self->{uid_base} + UID_BLOCK;
                 $end = $uid_end if $end > $uid_end;
                 $beg = $end if $beg > $end;
@@ -1093,14 +1099,14 @@ sub cmd_uid_search ($$$;) {
         if (!scalar(keys %$q)) {
                 $self->msg_more('* SEARCH');
                 my $beg = 1;
-                my $end = $ibx->mm->max // 0;
+                my $end = $ibx->over->max;
                 uid_clamp($self, \$beg, \$end);
                 long_response($self, \&uid_search_uid_range,
                                 $tag, \$beg, $end, $sql);
         } elsif (my $uid = $q->{uid}) {
                 if ($uid =~ /\A([0-9]+):([0-9]+|\*)\z/s) {
                         my ($beg, $end) = ($1, $2);
-                        $end = $ibx->mm->max if $end eq '*';
+                        $end = $ibx->over->max if $end eq '*';
                         uid_clamp($self, \$beg, \$end);
                         $self->msg_more('* SEARCH');
                         long_response($self, \&uid_search_uid_range,
diff --git a/lib/PublicInbox/IMAPD.pm b/lib/PublicInbox/IMAPD.pm
index 186ec7b0..e4dc90e8 100644
--- a/lib/PublicInbox/IMAPD.pm
+++ b/lib/PublicInbox/IMAPD.pm
@@ -44,7 +44,7 @@ sub imapd_refresh_ibx { # pi_config->each_inbox cb
         # this case is a 32-bit representation of the creation
         # date/time of the mailbox"
         defined($ibx->{uidvalidity} = $mm->created_at) or return;
-        PublicInbox::IMAP::ensure_ranges_exist($imapd, $ibx, $mm->max // 1);
+        PublicInbox::IMAP::ensure_ranges_exist($imapd, $ibx, $mm->max // 0);
 
         # preload to avoid fragmentation:
         $ibx->description;
diff --git a/lib/PublicInbox/Over.pm b/lib/PublicInbox/Over.pm
index 1faeff41..e0f20ea6 100644
--- a/lib/PublicInbox/Over.pm
+++ b/lib/PublicInbox/Over.pm
@@ -229,4 +229,34 @@ sub uid_range {
         $dbh->selectcol_arrayref($q, undef, $beg, $end);
 }
 
+sub max {
+        my ($self) = @_;
+        my $sth = $self->connect->prepare_cached(<<'', undef, 1);
+SELECT MAX(num) FROM over WHERE num > 0
+
+        $sth->execute;
+        $sth->fetchrow_array // 0;
+}
+
+sub imap_status {
+        my ($self, $uid_base, $uid_end) = @_;
+        my $dbh = $self->connect;
+        my $sth = $dbh->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, $sth->fetchrow_array // 0);
+}
+
 1;
diff --git a/t/over.t b/t/over.t
index 5586aa31..734fdaa3 100644
--- a/t/over.t
+++ b/t/over.t
@@ -10,6 +10,8 @@ use_ok 'PublicInbox::OverIdx';
 my ($tmpdir, $for_destroy) = tmpdir();
 my $over = PublicInbox::OverIdx->new("$tmpdir/over.sqlite3");
 $over->connect;
+is($over->max, 0, 'max is zero on new DB (scalar context)');
+is_deeply([$over->max], [0], 'max is zero on new DB (list context)');
 my $x = $over->next_tid;
 is(int($x), $x, 'integer tid');
 my $y = $over->next_tid;
@@ -58,6 +60,7 @@ foreach my $mid (qw(a b)) {
         my $msgs = [ map { $_->{num} } @{$over->get_thread($mid)} ];
         is_deeply([98, 99], $msgs, "linked messages by Message-ID: <$mid>");
 }
+isnt($over->max, 0, 'max is non-zero');
 
 $over->rollback_lazy;