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}

# Public method
# Optimized method to find all bindings matching a pattern
# See:
# Verborgh, Ruben, et al. Querying Datasets on the Web with High Availability. ISWC2014
# http://linkeddatafragments.org/publications/iswc2014.pdf
sub get_pattern {
    my ($self,$bgp,$context,%args) = @_;

    unless (defined $bgp) {
       RDF::LDF::Error->throw(text => "can't execute get_pattern for an empty pattern");
    }

    my (@triples)   = ($bgp->isa('RDF::Trine::Statement') or $bgp->isa('RDF::Query::Algebra::Filter'))
                    ? $bgp
                    : $bgp->triples;

    unless (@triples) {
        RDF::LDF::Error->throw(text => "can't execute get_pattern for an empty pattern");
    }

    my @vars = $bgp->referenced_variables;

    my @bgps = map { $self->_parse_triple_pattern($_)} @triples;

    my $sub = sub {
        state $it = $self->_find_variable_bindings(\@bgps);
        my $b = $it->();

        return undef unless $b;

        my $binding = RDF::Trine::VariableBindings->new({});

        for my $key (keys %$b) {
            my $val = $b->{$key};
            $key =~ s{^\?}{};
            $binding->set($key => $val);
        }

        $binding;
    };

    RDF::Trine::Iterator::Bindings->new($sub,\@vars);
}

sub _find_variable_bindings {
    my $self     = shift;
    my $bgps     = shift;
    my $bindings = shift // {};

    my $iterator = sub {
        state $it;
        state $results = sub {};

        my $ret;

        # Loop over all variabe bindings with multiple matches
        while (!defined($ret = $results->())) {
            unless (defined $it) {
                # Find the an binding iterator for the best pattern from $bgpgs
                ($it,$bgps) = $self->_find_variable_bindings_($bgps);

                return undef unless $it;
            }

            # Update all the other bgps with the current binding..
            my $this_binding = $it->();

            return undef unless $this_binding;

            $bindings = { %$bindings , %$this_binding };

            return $bindings unless @$bgps;

            # Apply all the bindings to the rest of the bgps;
            my $bgps_prime = $self->_apply_binding($this_binding,$bgps);

            $results = $self->_find_variable_bindings($bgps_prime,$bindings);
        }

        $ret;
    };

    $iterator;
}

# Given an array ref of patterns return the variable bindings for the
# pattern with the least number of triples.
#
#  my ($iterator, $rest) = $self->_find_variable_bindings([ {pattern} , {pattern} , ... ]);
#
#  where:
#
#  $iterator - Iterator for variable bindings for the winnnig pattern, or undef when no
#              patterns are provided or we get zero results
#
#  $rest     - An array ref of patterns not containing the best pattern
sub _find_variable_bindings_ {
    my ($self,$bgps) = @_;

    return (undef, undef) unless _is_array_ref($bgps) && @$bgps > 0;

    my ($pattern,$rest) = $self->_find_best_pattern($bgps);

    return (undef,undef) unless defined $pattern;

    my $it = $self->get_statements($pattern);

    # Build a mapping of variable bindings to Triple nodes. E.g.
    # {
    #    '?s' => 'subject' ,
    #    '?p' => 'predicate'  ,
    #    '?o' => 'object' ,
    #}
    my %pattern_var_map = map { $pattern->{$_} =~ /^\?/ ? ($pattern->{$_} , $_) : () } keys %$pattern;
    my $num_of_bindings = keys %pattern_var_map;

    my $sub = sub {
        my $triple = $it->();