# RDF::Query::Plan::Join::NestedLoop
# -----------------------------------------------------------------------------

=head1 NAME

RDF::Query::Plan::Join::NestedLoop - Executable query plan for nested loop joins.

=head1 VERSION

This document describes RDF::Query::Plan::Join::NestedLoop version 2.916.

=head1 METHODS

Beyond the methods documented below, this class inherits methods from the
L<RDF::Query::Plan::Join> class.

=over 4

=cut

package RDF::Query::Plan::Join::NestedLoop;

use strict;
use warnings;
use base qw(RDF::Query::Plan::Join);

use Log::Log4perl;
use Scalar::Util qw(blessed);
use Time::HiRes qw(gettimeofday tv_interval);

use RDF::Query::Error qw(:try);
use RDF::Query::ExecutionContext;

######################################################################

our ($VERSION);
BEGIN {
	$VERSION	= '2.916';
	$RDF::Query::Plan::Join::JOIN_CLASSES{ 'RDF::Query::Plan::Join::NestedLoop' }++;
}

######################################################################

=item C<< new ( $lhs, $rhs, $opt, [ \%logging_keys ] ) >>

=cut

sub new {
	my $class	= shift;
	my $lhs		= shift;
	my $rhs		= shift;
	my $opt		= shift;
	my $keys	= shift;
	if ($opt) {
		throw RDF::Query::Error::MethodInvocationError -text => "NestedLoop join does not support optional joins (use PushDownNestedLoop instead)";
	}
	my $self	= $class->SUPER::new( $lhs, $rhs, $opt );
	
	$self->[0]{logging_keys}	= $keys;
	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 => "NestedLoop join plan can't be executed while already open";
	}
	
	my $l		= Log::Log4perl->get_logger("rdf.query.plan.join.nestedloop");
	$self->[0]{start_time}	= [gettimeofday];
# 	if ($self->optional) {
# 		my (@inner, @outer);
# 		$self->rhs->execute( $context );
# 		while (my $row = $self->rhs->next) {
# 			$l->trace("loading inner row: " . $row);
# 			push(@inner, $row);
# 		}
# 		
# 		my @results;
# 		$self->lhs->execute( $context );
# 		while (my $outer = $self->lhs->next) {
# 			$l->trace("loading outer row: " . $outer);
# 			my $count	= 0;
# 			foreach my $inner (@inner) {
# 				if (my $joined = $inner->join( $outer )) {
# 					$count++;
# 					if ($l->is_trace) {
# 						$l->trace("joined bindings: $outer ⋈ $inner");
# 					}
# 	#				warn "-> joined\n";
# 					$self->[0]{count}++;
# 					push(@results, $joined);
# 				}
# 			}
# 			if ($count == 0) {
# 				# left-join branch
# 				push(@results, $outer);
# 			}
# 		}
# 		
# 		warn Dumper(\@results);
# 		
# 		$self->[0]{results}	= \@results;
# 	} else {
		my @inner;
		$self->rhs->execute( $context );
		while (my $row = $self->rhs->next) {
			$l->trace("loading inner row cache with: " . $row);
			push(@inner, $row);
		}
		$self->lhs->execute( $context );
		if ($self->lhs->state == $self->OPEN) {
			$self->[0]{inner}			= \@inner;
			$self->[0]{outer}			= $self->lhs;
			$self->[0]{inner_index}		= 0;
			$self->[0]{needs_new_outer}	= 1;
			$self->[0]{inner_count}		= 0;
			$self->[0]{count}			= 0;
			$self->[0]{logger}			= $context->logger;
			$self->state( $self->OPEN );
		} else {
			warn "no iterator in execute()";
		}
# 	}
#	warn '########################################';
	$self;
}

=item C<< next >>

=cut

sub next {
	my $self	= shift;
	unless ($self->state == $self->OPEN) {
		throw RDF::Query::Error::ExecutionError -text => "next() cannot be called on an un-open NestedLoop join";
	}
	
# 	if ($self->optional) {
# 		my $result	= shift(@{ $self->[0]{results} });
# 		if (my $d = $self->delegate) {
# 			$d->log_result( $self, $result );
# 		}
# 		return $result;
# 	}
	
	my $outer	= $self->[0]{outer};
	my $inner	= $self->[0]{inner};
	
	my $l		= Log::Log4perl->get_logger("rdf.query.plan.join.nestedloop");
	while (1) {
		if ($self->[0]{needs_new_outer}) {
			$self->[0]{outer_row}	= $outer->next;
			if (ref($self->[0]{outer_row})) {
				$self->[0]{needs_new_outer}	= 0;
				$self->[0]{inner_index}		= 0;
				$self->[0]{inner_count}		= 0;
	#			warn "got new outer row: " . Dumper($self->[0]{outer_row});
			} else {
				# we've exhausted the outer iterator. we're now done.
	#			warn "exhausted";
				return undef;
			}
		}
		
		while ($self->[0]{inner_index} < scalar(@$inner)) {
			my $inner_row	= $inner->[ $self->[0]{inner_index}++ ];
	#		warn "using inner row: " . Dumper($inner_row);
			if (my $joined = $inner_row->join( $self->[0]{outer_row} )) {
				if ($l->is_trace) {
					$l->trace("joined bindings: $inner_row ⋈ $self->[0]{outer_row}");
				}
#				warn "-> joined\n";
				$self->[0]{inner_count}++;
				$self->[0]{count}++;
				if (my $d = $self->delegate) {
					$d->log_result( $self, $joined );
				}
				return $joined;
			} else {
				$l->trace("failed to join bindings: $inner_row ⋈ $self->[0]{outer_row}");
			}
		}
		
		$self->[0]{needs_new_outer}	= 1;
	}
}

=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 NestedLoop join";
	}
	
	my $l		= Log::Log4perl->get_logger("rdf.query.plan.join.nestedloop");
	my $t0		= delete $self->[0]{start_time};
	my $count	= delete $self->[0]{count};
	if (my $log = delete $self->[0]{logger}) {
		$l->debug("logging nestedloop join execution statistics");
		my $elapsed = tv_interval ( $t0 );
		if (my $sparql = $self->logging_keys->{sparql}) {
			if ($l->is_trace) {
				$l->trace("- SPARQL: $sparql");
				$l->trace("- elapsed: $elapsed");
				$l->trace("- count: $count");
			}
			$log->push_key_value( 'execute_time-nestedloop', $sparql, $elapsed );
			$log->push_key_value( 'cardinality-nestedloop', $sparql, $count );
		}
		if (my $bf = $self->logging_keys->{bf}) {
			if ($l->is_trace) {
				$l->trace("- bf: $bf");
			}
			$log->push_key_value( 'cardinality-bf-nestedloop', $bf, $count );
		}
	}
	delete $self->[0]{inner};
	delete $self->[0]{outer};
	delete $self->[0]{inner_index};
	delete $self->[0]{needs_new_outer};
	delete $self->[0]{inner_count};
	$self->lhs->close();
	$self->rhs->close();
	$self->SUPER::close();
}

=item C<< plan_node_name >>

Returns the string name of this plan node, suitable for use in serialization.

=cut

sub plan_node_name {
	my $self	= shift;
	my $jtype	= $self->optional ? 'leftjoin' : 'join';
	return "nestedloop-$jtype";
}

=item C<< graph ( $g ) >>

=cut

sub graph {
	my $self	= shift;
	my $g		= shift;
	my $jtype	= $self->optional ? 'Left Join' : 'Join';
	my ($l, $r)	= map { $_->graph( $g ) } ($self->lhs, $self->rhs);
	$g->add_node( "$self", label => "$jtype (NL)" . $self->graph_labels );
	$g->add_edge( "$self", $l );
	$g->add_edge( "$self", $r );
	return "$self";
}


package RDF::Query::Plan::Join::NestedLoop::Left;

use strict;
use warnings;
use base qw(RDF::Query::Plan::Join::NestedLoop);

sub new {
	my $class	= shift;
	my $lhs		= shift;
	my $rhs		= shift;
	return $class->SUPER::new( $lhs, $rhs, 1 );
}


1;

__END__

=back

=head1 AUTHOR

 Gregory Todd Williams <gwilliams@cpan.org>

=cut
