/usr/share/perl5/RDF/Query/Plan/Union.pm is in librdf-query-perl 2.918-1.
This file is owned by root:root, with mode 0o644.
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# -----------------------------------------------------------------------------
=head1 NAME
RDF::Query::Plan::Union - Executable query plan for unions.
=head1 VERSION
This document describes RDF::Query::Plan::Union version 2.918.
=head1 METHODS
Beyond the methods documented below, this class inherits methods from the
L<RDF::Query::Plan> class.
=over 4
=cut
package RDF::Query::Plan::Union;
use strict;
use warnings;
use base qw(RDF::Query::Plan);
use Scalar::Util qw(blessed refaddr);
use RDF::Query::ExecutionContext;
######################################################################
our ($VERSION);
BEGIN {
$VERSION = '2.918';
}
######################################################################
=item C<< new ( $lhs, $rhs ) >>
=cut
sub new {
my $class = shift;
my ($lhs, $rhs) = @_;
my $self = $class->SUPER::new( [ $lhs, $rhs ] );
my %vars;
foreach my $v ($lhs->referenced_variables, $rhs->referenced_variables) {
$vars{ $v }++;
}
$self->[0]{referenced_variables} = [ keys %vars ];
return $self;
}
=item C<< execute ( $execution_context ) >>
=cut
sub execute ($) {
my $self = shift;
my $context = shift;
$self->[0]{delegate} = $context->delegate;
if ($self->state == $self->OPEN) {
throw RDF::Query::Error::ExecutionError -text => "BGP plan can't be executed while already open";
}
my $iter = $self->[1][0];
$iter->execute( $context );
if ($iter->state == $self->OPEN) {
$self->[0]{iter} = $iter;
$self->[0]{idx} = 0;
$self->[0]{context} = $context;
$self->state( $self->OPEN );
} else {
warn "no iterator in execute()";
}
$self;
}
=item C<< next >>
=cut
sub next {
my $self = shift;
my $l = Log::Log4perl->get_logger("rdf.query.plan.union");
unless ($self->state == $self->OPEN) {
throw RDF::Query::Error::ExecutionError -text => "next() cannot be called on an un-open BGP";
}
my $iter = $self->[0]{iter};
return undef unless ($iter);
my $row = $iter->next;
if (defined($row)) {
$l->trace( "union row: $row" );
if (my $d = $self->delegate) {
$d->log_result( $self, $row );
}
return $row;
} else {
$self->[0]{iter} = undef;
if ($self->[0]{idx} < $#{ $self->[1] }) {
$iter->close();
$self->[0]{idx}++;
my $index = $self->[0]{idx};
my $iter = $self->[1][ $index ];
$iter->execute( $self->[0]{context} );
if ($iter->state == $self->OPEN) {
$l->trace( "union moving to next branch" );
$self->[0]{iter} = $iter;
my $bindings = $self->next;
if (my $d = $self->delegate) {
$d->log_result( $self, $bindings );
}
return $bindings;
} else {
throw RDF::Query::Error::ExecutionError -text => "execute() on RHS of UNION failed during next()";
}
} else {
$l->trace( "union reached end of last branch" );
$iter->close();
delete $self->[0]{iter};
return undef;
}
}
}
=item C<< close >>
=cut
sub close {
my $self = shift;
unless ($self->state == $self->OPEN) {
throw RDF::Query::Error::ExecutionError -text => "close() cannot be called on an un-open BGP";
}
if (my $iter = $self->[0]{iter}) {
$iter->close();
delete $self->[0]{iter};
delete $self->[0]{idx};
}
$self->SUPER::close();
}
=item C<< lhs >>
Returns the left-hand-side plan to the union.
=cut
sub lhs {
my $self = shift;
return $self->[1][0];
}
=item C<< rhs >>
Returns the right-hand-side plan to the union.
=cut
sub rhs {
my $self = shift;
return $self->[1][1];
}
=item C<< distinct >>
Returns true if the pattern is guaranteed to return distinct results.
=cut
sub distinct {
return 0;
}
=item C<< ordered >>
Returns true if the pattern is guaranteed to return ordered results.
=cut
sub ordered {
return [];
}
=item C<< plan_node_name >>
Returns the string name of this plan node, suitable for use in serialization.
=cut
sub plan_node_name {
return 'union';
}
=item C<< plan_prototype >>
Returns a list of scalar identifiers for the type of the content (children)
nodes of this plan node. See L<RDF::Query::Plan> for a list of the allowable
identifiers.
=cut
sub plan_prototype {
my $self = shift;
return qw(P P);
}
=item C<< plan_node_data >>
Returns the data for this plan node that corresponds to the values described by
the signature returned by C<< plan_prototype >>.
=cut
sub plan_node_data {
my $self = shift;
my $expr = $self->[2];
return ($self->lhs, $self->rhs);
}
=item C<< graph ( $g ) >>
=cut
sub graph {
my $self = shift;
my $g = shift;
my ($l, $r) = map { $_->graph( $g ) } ($self->lhs, $self->rhs);
$g->add_node( "$self", label => "Union" . $self->graph_labels );
$g->add_edge( "$self", $l );
$g->add_edge( "$self", $r );
return "$self";
}
1;
__END__
=back
=head1 AUTHOR
Gregory Todd Williams <gwilliams@cpan.org>
=cut
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