filter meta query

$filter_meta_query = array(
	'relation' => 'AND',
	array(
		'key'     => 'agenda_data_futuras',
		'value'   => 'a:0:{}',
		'compare' => '!=',
	),
	array(
		'key'     => 'agenda_data_futuras',
		'compare' => '!=',
	),
);