Foreign::validate

public function validate($value, $primary, array $row, EntityField $field)
{
	$query = new EntityQuery($this->reference->getEntity());
	$query->setFilter(array('='.$this->reference->getName() => $value) + $this->filter);
	$query->setLimit(1);
	$result = $query->exec();

	if($result->fetch())
	{
		return true;
	}
	return 	new EntityFieldError($field, $this->getErrorMessage($value, $field), self::NOT_EXISTS);
}