search: remove {mset} option for ->mset method

The ->mset method always returns a Xapian mset nowadays, so
naming a parameter {mset} is too confusing.  As it does with
MiscSearch, setting the {relevance} parameter to -1 now sorts by
ascending docid order.  -2 is now supported for descending
docid order, too, since it may be useful for lei users.

1 files changed, 13 insertions, 11 deletions

diff --git a/lib/PublicInbox/Search.pm b/lib/PublicInbox/Search.pm
index ffd19a1f..fb3e9975 100644
--- a/lib/PublicInbox/Search.pm
+++ b/lib/PublicInbox/Search.pm
@@ -58,7 +58,11 @@ our $QP_FLAGS;
 our %X = map { $_ => 0 } qw(BoolWeight Database Enquire QueryParser Stem Query);
 our $Xap; # 'Search::Xapian' or 'Xapian'
 our $NVRP; # '$Xap::'.('NumberValueRangeProcessor' or 'NumberRangeProcessor')
-our $ENQ_ASCENDING;
+
+# ENQ_DESCENDING and ENQ_ASCENDING weren't in SWIG Xapian.pm prior to 1.4.16,
+# let's hope the ABI is stable
+our $ENQ_DESCENDING = 0;
+our $ENQ_ASCENDING = 1;
 
 sub load_xapian () {
         return 1 if defined $Xap;
@@ -84,12 +88,6 @@ sub load_xapian () {
                         'NumberRangeProcessor' : 'NumberValueRangeProcessor');
                 $X{$_} = $Xap.'::'.$_ for (keys %X);
 
-                # ENQ_ASCENDING doesn't seem exported by SWIG Xapian.pm,
-                # so lets hope this part of the ABI is stable because it's
-                # just an integer:
-                $ENQ_ASCENDING = $x eq 'Xapian' ?
-                                1 : Search::Xapian::ENQ_ASCENDING();
-
                 *sortable_serialise = $x.'::sortable_serialise';
                 *sortable_unserialise = $x.'::sortable_unserialise';
                 # n.b. FLAG_PURE_NOT is expensive not suitable for a public
@@ -344,13 +342,17 @@ sub _enquire_once { # retry_reopen callback
         $enquire->set_query($query);
         $opts ||= {};
         my $desc = !$opts->{asc};
-        if (($opts->{mset} || 0) == 2) { # mset == 2: ORDER BY docid/UID
+        my $rel = $opts->{relevance} // 0;
+        if ($rel == -1) { # ORDER BY docid/UID
+                $enquire->set_weighting_scheme($X{BoolWeight}->new);
                 $enquire->set_docid_order($ENQ_ASCENDING);
+        } elsif ($rel == 0) {
+                $enquire->set_sort_by_value_then_relevance(TS, $desc);
+        } elsif ($rel == -2) {
                 $enquire->set_weighting_scheme($X{BoolWeight}->new);
-        } elsif ($opts->{relevance}) {
+                $enquire->set_docid_order($ENQ_DESCENDING);
+        } else { # rel > 0
                 $enquire->set_sort_by_relevance_then_value(TS, $desc);
-        } else {
-                $enquire->set_sort_by_value_then_relevance(TS, $desc);
         }
 
         # `mairix -t / --threads' or JMAP collapseThreads