search: support SWIG-generated Xapian.pm

Xapian upstream is slowly phasing out the XS-based Search::Xapian
in favor of the SWIG-generated "Xapian" package.  While Debian and
both FreeBSD have Search::Xapian, OpenBSD only includes the "Xapian"
binding.

More information about the status of the "Xapian" Perl module here:
https://trac.xapian.org/ticket/523

1 files changed, 39 insertions, 18 deletions

diff --git a/lib/PublicInbox/Search.pm b/lib/PublicInbox/Search.pm
index 88c8dc70..65c6ee83 100644
--- a/lib/PublicInbox/Search.pm
+++ b/lib/PublicInbox/Search.pm
@@ -17,20 +17,42 @@ use PublicInbox::MIME;
 use PublicInbox::MID qw/id_compress/;
 use PublicInbox::Over;
 my $QP_FLAGS;
+our %X = map { $_ => 0 } qw(BoolWeight Database Enquire
+                        NumberValueRangeProcessor QueryParser Stem);
+our $Xap; # 'Search::Xapian' or 'Xapian'
+my $ENQ_ASCENDING;
+
 sub load_xapian () {
-        $QP_FLAGS ||= eval {
-                require Search::Xapian;
-                Search::Xapian->import(qw(:standard));
+        return 1 if defined $Xap;
+        for my $x (qw(Search::Xapian Xapian)) {
+                eval "require $x";
+                next if $@;
+
+                $x->import(qw(:standard));
+                $Xap = $x;
+                $X{$_} = $Xap.'::'.$_ 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();
+
+                # for SearchMsg:
+                *PublicInbox::SearchMsg::sortable_unserialise =
+                                                $Xap.'::sortable_unserialise';
                 # n.b. FLAG_PURE_NOT is expensive not suitable for a public
                 # website as it could become a denial-of-service vector
                 # FLAG_PHRASE also seems to cause performance problems chert
                 # (and probably earlier Xapian DBs).  glass seems fine...
                 # TODO: make this an option, maybe?
                 # or make indexlevel=medium as default
-                FLAG_PHRASE()|FLAG_BOOLEAN()|FLAG_LOVEHATE()|FLAG_WILDCARD();
-        };
-};
+                $QP_FLAGS = FLAG_PHRASE() | FLAG_BOOLEAN() | FLAG_LOVEHATE() |
+                                FLAG_WILDCARD();
+                last;
+        }
+        undef;
+}
 
 # This is English-only, everything else is non-standard and may be confused as
 # a prefix common in patch emails
@@ -148,7 +170,7 @@ sub _xdb ($) {
         if ($self->{version} >= 2) {
                 foreach my $shard (<$dir/*>) {
                         -d $shard && $shard =~ m!/[0-9]+\z! or next;
-                        my $sub = Search::Xapian::Database->new($shard);
+                        my $sub = $X{Database}->new($shard);
                         if ($xdb) {
                                 $xdb->add_database($sub);
                         } else {
@@ -158,7 +180,7 @@ sub _xdb ($) {
                 }
         } else {
                 $slow_phrase = -f "$dir/iamchert";
-                $xdb = Search::Xapian::Database->new($dir);
+                $xdb = $X{Database}->new($dir);
         }
         $$qpf |= FLAG_PHRASE() unless $slow_phrase;
         $xdb;
@@ -222,7 +244,7 @@ sub retry_reopen {
                 }
                 # Exception: The revision being read has been discarded -
                 # you should call Xapian::Database::reopen()
-                if (ref($@) eq 'Search::Xapian::DatabaseModifiedError') {
+                if (ref($@) =~ /\bDatabaseModifiedError\b/) {
                         warn "reopen try #$i on $@\n";
                         reopen($self);
                 } else {
@@ -243,13 +265,13 @@ sub _do_enquire {
 sub _enquire_once {
         my ($self, $query, $opts) = @_;
         my $xdb = xdb($self);
-        my $enquire = Search::Xapian::Enquire->new($xdb);
+        my $enquire = $X{Enquire}->new($xdb);
         $enquire->set_query($query);
         $opts ||= {};
         my $desc = !$opts->{asc};
         if (($opts->{mset} || 0) == 2) {
-                $enquire->set_docid_order(Search::Xapian::ENQ_ASCENDING());
-                $enquire->set_weighting_scheme(Search::Xapian::BoolWeight->new);
+                $enquire->set_docid_order($ENQ_ASCENDING);
+                $enquire->set_weighting_scheme($X{BoolWeight}->new);
         } elsif ($opts->{relevance}) {
                 $enquire->set_sort_by_relevance_then_value(TS, $desc);
         } else {
@@ -268,7 +290,7 @@ sub _enquire_once {
 }
 
 # read-write
-sub stemmer { Search::Xapian::Stem->new($LANG) }
+sub stemmer { $X{Stem}->new($LANG) }
 
 # read-only
 sub qp {
@@ -278,16 +300,15 @@ sub qp {
         return $qp if $qp;
         my $xdb = xdb($self);
         # new parser
-        $qp = Search::Xapian::QueryParser->new;
+        $qp = $X{QueryParser}->new;
         $qp->set_default_op(OP_AND());
         $qp->set_database($xdb);
         $qp->set_stemmer($self->stemmer);
         $qp->set_stemming_strategy(STEM_SOME());
         $qp->set_max_wildcard_expansion(100);
-        $qp->add_valuerangeprocessor(
-                Search::Xapian::NumberValueRangeProcessor->new(YYYYMMDD, 'd:'));
-        $qp->add_valuerangeprocessor(
-                Search::Xapian::NumberValueRangeProcessor->new(DT, 'dt:'));
+        my $nvrp = $X{NumberValueRangeProcessor};
+        $qp->add_valuerangeprocessor($nvrp->new(YYYYMMDD, 'd:'));
+        $qp->add_valuerangeprocessor($nvrp->new(DT, 'dt:'));
 
         while (my ($name, $prefix) = each %bool_pfx_external) {
                 $qp->add_boolean_prefix($name, $_) foreach split(/ /, $prefix);