RDF::Query::Plan::Union - Executable query plan for unions.
Index
Code Index:
NAME
RDF::Query::Plan::Union - Executable query plan for unions.
VERSION
This document describes RDF::Query::Plan::Union version 2.907.
METHODS
Beyond the methods documented below, this class inherits methods from the
RDF::Query::Plan class.
new ( $lhs, $rhs )execute ( $execution_context )nextcloselhs-
Returns the left-hand-side plan to the union.
rhs-
Returns the right-hand-side plan to the union.
distinct-
Returns true if the pattern is guaranteed to return distinct results.
ordered-
Returns true if the pattern is guaranteed to return ordered results.
plan_node_name-
Returns the string name of this plan node, suitable for use in serialization.
plan_prototype-
Returns a list of scalar identifiers for the type of the content (children)
nodes of this plan node. See RDF::Query::Plan for a list of the allowable
identifiers.
plan_node_data-
Returns the data for this plan node that corresponds to the values described by
the signature returned by plan_prototype.
graph ( $g )
AUTHOR
Gregory Todd Williams <gwilliams@cpan.org>
# RDF::Query::Plan::Union
# -----------------------------------------------------------------------------
package RDF::Query::Plan::Union;
use strict;
use warnings;
use base qw(RDF::Query::Plan);
use Scalar::Util qw(blessed refaddr);
use RDF::Query::ExecutionContext;
######################################################################
our ($VERSION);
BEGIN {
$VERSION = '2.907';
}
######################################################################
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 $self;
}
sub execute ($) {
my $self = shift;
my $context = shift;
if ($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;
}
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" );
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;
return $self->next;
} 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;
}
}
}
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();
}
sub lhs {
my $self = shift;
return $self->[1][0];
}
sub rhs {
my $self = shift;
return $self->[1][1];
}
sub distinct {
return 0;
}
sub ordered {
return [];
}
sub plan_node_name {
return 'union';
}
sub plan_prototype {
my $self = shift;
return qw(P P);
}
sub plan_node_data {
my $self = shift;
my $expr = $self->[2];
return ($self->lhs, $self->rhs);
}
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__