my @columns = ( "id", "project", "jobset", "job", "system", "finished", "drvpath", "timestamp", "buildstatus" );

my @columns =
    ( "id", "project", "jobset", "job", "system", "finished", "drvpath", "timestamp", "buildstatus"
    , { "outpaths" => \ "(select string_agg(path, ' ') from BuildOutputs where build = me.id)" }
    );

        foreach my $out ($build->buildoutputs->all) {
            if (isValidPath($out->path)) {
                addRoot $out->path;

        foreach my $path (split / /, $build->get_column('outpaths')) {
            if (isValidPath($path)) {
                addRoot $path;

                print STDERR "    warning: output ", $out->path, " has disappeared\n" if $build->finished;

                print STDERR "    warning: output ", $path, " has disappeared\n" if $build->finished;