miscsearch: index UIDVALIDITY, use as startup cache

This brings -nntpd startup time down from ~35s to ~5s with 50K
inboxes.

Further improvements ought to be possible with deeper changes to
MiscIdx, since -mda having to load every inbox seems unreasonable;
but this general change is fairly unintrusive.

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/PublicInbox/NNTPD.pm b/lib/PublicInbox/NNTPD.pm
index 7f9a1d58..6907a03c 100644
--- a/lib/PublicInbox/NNTPD.pm
+++ b/lib/PublicInbox/NNTPD.pm
@@ -36,10 +36,12 @@ sub refresh_groups {
         my ($self, $sig) = @_;
         my $pi_cfg = $sig ? PublicInbox::Config->new : $self->{pi_cfg};
         my $groups = $pi_cfg->{-by_newsgroup}; # filled during each_inbox
+        my $cache = eval { $pi_cfg->ALL->misc->nntpd_cache_load } // {};
         $pi_cfg->each_inbox(sub {
                 my ($ibx) = @_;
                 my $ngname = $ibx->{newsgroup} // return;
-                if ($ibx->nntp_usable) {
+                my $ce = $cache->{$ngname};
+                if (($ce and (%$ibx = (%$ibx, %$ce))) || $ibx->nntp_usable) {
                         # only valid if msgmap and over works
                         # preload to avoid fragmentation:
                         $ibx->description;