nntp: xref: use ->ALL extindex if available

Getting Xref for cross-posted messages is an O(n) operation
where `n' is the number of newsgroups on the server.  This works
acceptably when there are dozens of groups, but would be
unnacceptable when there's tens of thousands of newsgroups.

With ~140 newsgroups, a lore.kernel.org mirror already handles
"XHDR Xref $MESSAGE_ID" requests around 30% faster after
creating the xref3.idx_nntp index.

The SQL additions to ExtSearch.pm may be a bit strange and
seem more appropriate for Over.pm; however it currently makes
sense to me since those bits of over.sqlite3 access are
exclusive to ExtSearch and can't be used by traditional
v1/v2 inboxes...

5 files changed, 116 insertions, 15 deletions

diff --git a/lib/PublicInbox/ExtSearch.pm b/lib/PublicInbox/ExtSearch.pm
index dd93cd32..20ec3224 100644
--- a/lib/PublicInbox/ExtSearch.pm
+++ b/lib/PublicInbox/ExtSearch.pm
@@ -11,6 +11,7 @@ use PublicInbox::Over;
 use PublicInbox::Inbox;
 use File::Spec ();
 use PublicInbox::MiscSearch;
+use DBI qw(:sql_types); # SQL_BLOB
 
 # for ->reopen, ->mset, ->mset_to_artnums
 use parent qw(PublicInbox::Search);
@@ -49,6 +50,61 @@ sub git {
         $self->{git} //= PublicInbox::Git->new("$self->{topdir}/ALL.git");
 }
 
+# returns an arrayref of [ $NEWSGROUP_NAME:$ART_NO ] using
+# the `xref3' table
+sub nntp_xref_for { # NNTP only
+        my ($self, $xibx, $xsmsg) = @_;
+        my $dbh = over($self)->dbh;
+
+        my $sth = $dbh->prepare_cached(<<'', undef, 1);
+SELECT ibx_id FROM inboxes WHERE eidx_key = ? LIMIT 1
+
+        $sth->execute($xibx->{newsgroup});
+        my $xibx_id = $sth->fetchrow_array // do {
+                warn "W: `$xibx->{newsgroup}' not found in $self->{topdir}\n";
+                return;
+        };
+
+        $sth = $dbh->prepare_cached(<<'', undef, 1);
+SELECT docid FROM xref3 WHERE oidbin = ? AND xnum = ? AND ibx_id = ? LIMIT 1
+
+        $sth->bind_param(1, pack('H*', $xsmsg->{blob}), SQL_BLOB);
+        $sth->bind_param(2, $xsmsg->{num});
+        $sth->bind_param(3, $xibx_id);
+        $sth->execute;
+        my $docid = $sth->fetchrow_array // do {
+                warn <<EOF;
+W: `$xibx->{newsgroup}:$xsmsg->{num}' not found in $self->{topdir}"
+EOF
+                return;
+        };
+
+        # LIMIT is number of newsgroups on server:
+        $sth = $dbh->prepare_cached(<<'', undef, 1);
+SELECT ibx_id,xnum FROM xref3 WHERE docid = ?
+
+        $sth->execute($docid);
+        my $rows = $sth->fetchall_arrayref;
+
+        my $eidx_key_sth = $dbh->prepare_cached(<<'', undef, 1);
+SELECT eidx_key FROM inboxes WHERE ibx_id = ? LIMIT 1
+
+        my %xref = map {
+                my ($ibx_id, $xnum) = @$_;
+                if ($ibx_id == $xibx_id) {
+                        ();
+                } else {
+                        $eidx_key_sth->execute($ibx_id);
+                        my $eidx_key = $eidx_key_sth->fetchrow_array;
+
+                        # only include if there's a newsgroup name
+                        $eidx_key && index($eidx_key, '/') >= 0 ?
+                                () : ($eidx_key => $xnum)
+                }
+        } @$rows;
+        [ map { "$_:$xref{$_}" } sort keys %xref ]; # match NNTP LIST order
+}
+
 sub mm { undef }
 
 sub altid_map { {} }
diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 39ff5257..8eec6b91 100644
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -413,14 +413,21 @@ sub xref ($$$) {
         my $nntpd = $self->{nntpd};
         my $cur_ngname = $cur_ibx->{newsgroup};
         my $ret = "$nntpd->{servername} $cur_ngname:$smsg->{num}";
-
-        my $mid = $smsg->{mid};
-        my $groups = $nntpd->{pi_config}->{-by_newsgroup};
-        for my $xngname (@{$nntpd->{groupnames}}) {
-                next if $cur_ngname eq $xngname;
-                my $xibx = $groups->{$xngname} or next;
-                my $num = eval { $xibx->mm->num_for($mid) } or next;
-                $ret .= " $xngname:$num";
+        if (my $ALL = $nntpd->{pi_config}->ALL) {
+                if (my $ary = $ALL->nntp_xref_for($cur_ibx, $smsg)) {
+                        $ret .= join(' ', '', @$ary) if scalar(@$ary);
+                }
+                # better off wrong than slow if there's thousands of groups,
+                # so no fallback to the slow path below:
+        } else { # slow path
+                my $mid = $smsg->{mid};
+                my $groups = $nntpd->{pi_config}->{-by_newsgroup};
+                for my $xngname (@{$nntpd->{groupnames}}) {
+                        next if $cur_ngname eq $xngname;
+                        my $xibx = $groups->{$xngname} or next;
+                        my $num = eval { $xibx->mm->num_for($mid) } or next;
+                        $ret .= " $xngname:$num";
+                }
         }
         $ret;
 }
diff --git a/lib/PublicInbox/OverIdx.pm b/lib/PublicInbox/OverIdx.pm
index 173e3220..8bec08da 100644
--- a/lib/PublicInbox/OverIdx.pm
+++ b/lib/PublicInbox/OverIdx.pm
@@ -542,6 +542,11 @@ CREATE TABLE IF NOT EXISTS xref3 (
 
         $dbh->do('CREATE INDEX IF NOT EXISTS idx_docid ON xref3 (docid)');
 
+        # performance critical, this is not UNIQUE since we may need to
+        # tolerate some old bugs from indexing mirrors
+        $dbh->do('CREATE INDEX IF NOT EXISTS idx_nntp ON '.
+                'xref3 (oidbin,xnum,ibx_id)');
+
                 $dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS eidx_meta (
         key VARCHAR(255) PRIMARY KEY,
diff --git a/t/extsearch.t b/t/extsearch.t
index 778ba32d..f9f74e5c 100644
--- a/t/extsearch.t
+++ b/t/extsearch.t
@@ -11,6 +11,8 @@ require_git(2.6);
 require_mods(qw(DBD::SQLite Search::Xapian));
 use_ok 'PublicInbox::ExtSearch';
 use_ok 'PublicInbox::ExtSearchIdx';
+my $sock = tcp_server();
+my $host_port = $sock->sockhost . ':' . $sock->sockport;
 my ($home, $for_destroy) = tmpdir();
 local $ENV{HOME} = $home;
 mkdir "$home/.public-inbox" or BAIL_OUT $!;
@@ -35,7 +37,7 @@ seek($fh, 0, SEEK_SET) or BAIL_OUT $!;
 
 run_script(['-mda', '--no-precheck'], $env, { 0 => $fh }) or BAIL_OUT '-mda';
 
-ok(run_script([qw(-init -V1 v1test), "$home/v1test",
+ok(run_script([qw(-init -V1 v1test --newsgroup v1.example), "$home/v1test",
         'http://example.com/v1test', $v1addr ]), 'v1test init');
 
 $eml->header_set('List-Id', '<v1.example.com>');
@@ -51,6 +53,36 @@ run_script(['-index', "$home/v1test"]) or BAIL_OUT "index $?";
 
 ok(run_script([qw(-extindex --all), "$home/extindex"]), 'extindex init');
 
+
+{ # TODO: -extindex should write this to config
+        open $fh, '>>', "$home/.public-inbox/config" or BAIL_OUT $!;
+        print $fh <<EOF or BAIL_OUT $!;
+; for ->ALL
+[extindex "all"]
+        topdir = $home/extindex
+EOF
+        close $fh or BAIL_OUT $!;
+
+        my $pi_cfg = PublicInbox::Config->new;
+        $pi_cfg->fill_all;
+        ok($pi_cfg->ALL, '->ALL');
+        my $ibx = $pi_cfg->{-by_newsgroup}->{'v2.example'};
+        my $ret = $pi_cfg->ALL->nntp_xref_for($ibx, $ibx->over->get_art(1));
+        is_deeply($ret, ['v1.example:1'], '->nntp_xref_for');
+}
+
+SKIP: {
+        require_mods(qw(Net::NNTP), 1);
+        my ($out, $err) = ("$home/nntpd.out.log", "$home/nntpd.err.log");
+        my $cmd = [ '-nntpd', '-W0' ]; #, "--stdout=$out", "--stderr=$err" ];
+        my $td = start_script($cmd, undef, { 3 => $sock });
+        my $n = Net::NNTP->new($host_port);
+        $n->group('v1.example');
+        my $res = $n->head(1);
+        @$res = grep(/^Xref: /, @$res);
+        like($res->[0], qr/ v1\.example:1 v2\.example:1/, 'nntp_xref works');
+}
+
 my $es = PublicInbox::ExtSearch->new("$home/extindex");
 {
         my $smsg = $es->over->get_art(1);
@@ -58,7 +90,7 @@ my $es = PublicInbox::ExtSearch->new("$home/extindex");
         is($es->over->get_art(2), undef, 'only one added');
         my $xref3 = $es->over->get_xref3(1);
         like($xref3->[0], qr/\A\Qv2.example\E:1:/, 'order preserved 1');
-        like($xref3->[1], qr!\A\Q$home/v1test\E:1:!, 'order preserved 2');
+        like($xref3->[1], qr/\A\Qv1.example\E:1:/, 'order preserved 2');
         is(scalar(@$xref3), 2, 'only to entries');
 }
 
@@ -93,9 +125,5 @@ my @it = $misc->mset('')->items;
 is(scalar(@it), 2, 'two inboxes');
 like($it[0]->get_document->get_data, qr/v2test/, 'docdata matched v2');
 like($it[1]->get_document->get_data, qr/v1test/, 'docdata matched v1');
-my $pi_cfg = PublicInbox::Config->new;
-$pi_cfg->fill_all;
-my $ret = $misc->newsgroup_matches('', $pi_cfg);
-is_deeply($pi_cfg->{-by_newsgroup}, $ret, '->newsgroup_matches');
 
 done_testing;
diff --git a/t/nntp.t b/t/nntp.t
index 9a482acb..91a2aff7 100644
--- a/t/nntp.t
+++ b/t/nntp.t
@@ -8,6 +8,7 @@ use PublicInbox::Eml;
 require_mods(qw(DBD::SQLite Data::Dumper));
 use_ok 'PublicInbox::NNTP';
 use_ok 'PublicInbox::Inbox';
+use PublicInbox::Config;
 
 {
         sub quote_str {
@@ -110,7 +111,11 @@ use_ok 'PublicInbox::Inbox';
         my $mime = PublicInbox::Eml->new("Message-ID: <$mid>\r\n\r\n");
         my $hdr = $mime->header_obj;
         my $mock_self = {
-                nntpd => { grouplist => [], servername => 'example.com' },
+                nntpd => {
+                        grouplist => [],
+                        servername => 'example.com',
+                        pi_config => bless {}, 'PublicInbox::Config',
+                },
                 ng => $ng,
         };
         my $smsg = { num => 1, mid => $mid, nntp => $mock_self, -ibx => $ng };