isearch: emulate per-inbox search with ->ALL

Using "eidx_key:" boolean prefix to limit results to a given
inbox, we can use ->ALL to emulate and replace per-Inbox
xap15/[0-9] search indices.

With this change, the presence of "extindex.all.topdir" in the
$PI_CONFIG will cause the WWW code to use that extindex and
ignore per-inbox Xapian DBs in xap15/[0-9].

Unfortunately IMAP search still requires old per-inbox indices,
for now.  Mapping extindex Xapian docids to per-Inbox UIDs and
vice-versa is proving tricky.  Fortunately, IMAP search is
rarely used and optional.  The RFCs don't specify expensive
phrase search, either, so `indexlevel=medium' can be used in
per-inbox Xapian indices to save space.

For primarily WWW (and future JMAP) users; this should result in
significant disk space, FD, and page cache footprint savings for
large instances with many inboxes and many cross-posted
messages.

1 files changed, 4 insertions, 0 deletions

diff --git a/lib/PublicInbox/Config.pm b/lib/PublicInbox/Config.pm
index ba0ead6e..1844f8b2 100644
--- a/lib/PublicInbox/Config.pm
+++ b/lib/PublicInbox/Config.pm
@@ -477,6 +477,10 @@ EOF
                         push @$repo_objs, $repo if $repo;
                 }
         }
+        if (my $es = ALL($self)) {
+                require PublicInbox::Isearch;
+                $ibx->{isrch} = PublicInbox::Isearch->new($ibx, $es);
+        }
         $self->{-by_eidx_key}->{$ibx->eidx_key} = $ibx;
 }