Блок фильтров это модуль blocklayered.
Таблица индексов цен
private static function installPriceIndexTable()
{
Db::getInstance()->execute('DROP TABLE IF EXISTS `'._DB_PREFIX_.'layered_price_index`');
Db::getInstance()->execute('
CREATE TABLE `'._DB_PREFIX_.'layered_price_index` (
`id_product` INT NOT NULL,
`id_currency` INT NOT NULL,
`id_shop` INT NOT NULL,
`price_min` INT NOT NULL,
`price_max` INT NOT NULL,
PRIMARY KEY (`id_product`, `id_currency`, `id_shop`),
INDEX `id_currency` (`id_currency`),
INDEX `price_min` (`price_min`), INDEX `price_max` (`price_max`)
) ENGINE='._MYSQL_ENGINE_.' DEFAULT CHARSET=utf8;');
}