Base::prepareQueryFields

protected function prepareQueryFields(array $select, array $filter, array $order)
{
	if ($this->useCatalog)
	{
		$select = $this->convertSelect($select);
		$order = $this->convertOrder($order);
		$filter = $this->convertFilter($filter);
		$filter = CProductQueryBuilder::modifyFilterFromOrder(
			$filter,
			$order,
			['QUANTITY' => $this->arParams['SHOW_PRICE_COUNT']]
		);
	}

	if (!empty($select))
	{
		$select = array_unique($select);
	}

	return [
		'SELECT' => $select,
		'FILTER' => $filter,
		'ORDER' => $order
	];
}