# RDF::Query::Algebra::Union
# -----------------------------------------------------------------------------
=head1 NAME
RDF::Query::Algebra::Union - Algebra class for Union patterns
=head1 VERSION
This document describes RDF::Query::Algebra::Union version 2.911.
=cut
package RDF::Query::Algebra::Union;
use strict;
use warnings;
no warnings 'redefine';
use base qw(RDF::Query::Algebra);
use Data::Dumper;
use Set::Scalar;
use Log::Log4perl;
use Scalar::Util qw(blessed);
use Carp qw(carp croak confess);
######################################################################
our ($VERSION);
BEGIN {
$VERSION = '2.911';
}
######################################################################
=head1 METHODS
Beyond the methods documented below, this class inherits methods from the
L<RDF::Query::Algebra> class.
=over 4
=cut
=item C<new ( $left, $right )>
Returns a new Union structure.
=cut
sub new {
my $class = shift;
my $left = shift;
my $right = shift;
return bless( [ 'UNION', $left, $right ], $class );
}
=item C<< construct_args >>
Returns a list of arguments that, passed to this class' constructor,
will produce a clone of this algebra pattern.
=cut
sub construct_args {
my $self = shift;
return ($self->first, $self->second);
}
=item C<< first >>
Returns the first pattern (LHS) of the union.
=cut
sub first {
my $self = shift;
return $self->[1];
}
=item C<< second >>
Returns the second pattern (RHS) of the union.
=cut
=item C<< patterns >>
Returns the two patterns belonging to the UNION pattern.
=cut
sub patterns {
my $self = shift;
return ($self->first, $self->second);
}
sub second {
my $self = shift;
return $self->[2];
}
=item C<< sse >>
Returns the SSE string for this algebra expression.
=cut
sub sse {
my $self = shift;
my $context = shift;
my $prefix = shift || '';
my $indent = $context->{indent} || ' ';
return sprintf(
"(union\n${prefix}${indent}%s\n${prefix}${indent}%s)",
$self->first->sse( $context, "${prefix}${indent}" ),
$self->second->sse( $context, "${prefix}${indent}" )
);
}
=item C<< as_sparql >>
Returns the SPARQL string for this algebra expression.
=cut
sub as_sparql {
my $self = shift;
my $context = shift;
my $indent = shift;
my $string = sprintf(
"%s\n${indent}UNION\n${indent}%s",
$self->first->as_sparql( { %$context, force_ggp_braces => 1 }, $indent ),
$self->second->as_sparql( { %$context, force_ggp_braces => 1 }, $indent ),
);
return $string;
}
=item C<< as_hash >>
Returns the query as a nested set of plain data structures (no objects).
=cut
sub as_hash {
my $self = shift;
my $context = shift;
return {
type => lc($self->type),
patterns => [ map { $_->as_hash } $self->patterns ],
};
}
=item C<< type >>
Returns the type of this algebra expression.
=cut
sub type {
return 'UNION';
}
=item C<< referenced_variables >>
Returns a list of the variable names used in this algebra expression.
=cut
sub referenced_variables {
my $self = shift;
return RDF::Query::_uniq($self->first->referenced_variables, $self->second->referenced_variables);
}
=item C<< potentially_bound >>
Returns a list of the variable names used in this algebra expression that will
bind values during execution.
=cut
sub potentially_bound {
my $self = shift;
return RDF::Query::_uniq($self->first->potentially_bound, $self->second->potentially_bound);
}
=item C<< definite_variables >>
Returns a list of the variable names that will be bound after evaluating this algebra expression.
=cut
sub definite_variables {
my $self = shift;
my $seta = Set::Scalar->new( $self->first->definite_variables );
my $setb = Set::Scalar->new( $self->second->definite_variables );
return $seta->intersection( $setb )->members;
}
1;
__END__
=back
=head1 AUTHOR
Gregory Todd Williams <gwilliams@cpan.org>
=cut