CEntityQuery::checkChainsAggregation

protected function checkChainsAggregation($chain)
{
	$chains = is_array($chain) ? $chain : array($chain);

	foreach ($chains as $chain)
	{
		$last = $chain->getLastElement();
		$is_aggr = $last->getValue() instanceof CExpressionEntityField && $last->getValue()->IsAggregated();

		if ($is_aggr)
		{
			return true;
		}
	}

	return false;
}