Posts2Posts plugin p2p_query

gistfile1.php

// new WP_Query( array( 'p2p_query'=>array( array('p2p_type'=>'', 'direction'=>'') ) ) );
// set p2p_type to an existing registered p2p_type
// set direction to the direction for queries post type in the connection p2p_type
// this will return only items that have connections from the p2p_type

add_filter('posts_join', 'mu_p2p_join', 10, 2);
add_filter('posts_where', 'my_p2p_where', 10, 2);

function my_p2p_join($join, $query) {
	if (isset($query->query_vars['p2p_query'])) {
		global $wpdb;
		
		foreach ($query->query_vars['p2p_query'] as $i => $p2p_query) {
			$join .= " INNER JOIN `$wpdb->p2p` AS `p2p_$i` ON (`$wpdb->posts`.`ID` = `p2p_$i`.`{$p2p_query['direction']}`) ";
		}
	}
	
	return $join;
}

function my_p2p_where($where, $query) {
	if (isset($query->query_vars['p2p_query'])) {
		global $wpdb;
		
		foreach ($query->query_vars['p2p_query'] as $i => $p2p_query) {
			$where .= " AND `p2p_$i`.`p2p_type` = '{$p2p_query['p2p_type']}' ";
		}
	}
	
	return $where;
}