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=encoding utf8

=head1 NAME

Lucy::Search::PolyQuery - Base class for composite Query objects.

=head1 SYNOPSIS

    sub walk {
        my $query = shift;
        if ( $query->isa("Lucy::Search::PolyQuery") ) {
            if    ( $query->isa("Lucy::Search::ORQuery") )  { ... }
            elsif ( $query->isa("Lucy::Search::ANDQuery") ) { ... }
            elsif ( $query->isa("Lucy::Search::RequiredOptionalQuery") ) {
                ...
            }
            elsif ( $query->isa("Lucy::Search::NOTQuery") ) { ... }
        }
        else { ... }
    }

=head1 DESCRIPTION

PolyQuery serves as a shared base class for
L<ANDQuery|Lucy::Search::ANDQuery>,
L<ORQuery|Lucy::Search::ORQuery>,
L<NOTQuery|Lucy::Search::NOTQuery>, and
L<RequiredOptionalQuery|Lucy::Search::RequiredOptionalQuery>.  All of
these classes may serve as nodes in composite Query with a tree structure
which may be walked.

=head1 METHODS

=head2 add_child

    $poly_query->add_child($query);

Add a child Query node.

=head1 INHERITANCE

Lucy::Search::PolyQuery isa L<Lucy::Search::Query> isa Clownfish::Obj.

=cut