CExpressionEntityField::checkAggregation

static function checkAggregation($expression)
{
	if (empty(self::$aggrFunctions))
	{
		self::$aggrFunctions = array_unique(array_merge(
			self::$aggrFunctionsMYSQL, self::$aggrFunctionsMSSQL, self::$aggrFunctionsORACLE
		));
	}

	// should remove subqueries from expression here: EXISTS(..(..)..), (SELECT ..(..)..)

	if (preg_match('/(?:^|[^a-z0-9_])EXISTSs*(/', $expression))
	{
		return false;
	}
	else
	{
		preg_match_all('/(?:^|[^a-z0-9_])(?