ActiveRecord Auto Aliasing

request.sql

-- shipments is aliased to shipments_shipping_items by AR because it is present in the subquery
-- this particular query fails because we join business_sites on shipments but shipments was aliased shipments_shipping_items
SELECT 
    `shipping_items`.*
FROM
    `shipping_items`
        INNER JOIN
    `item_variants` ON `item_variants`.`id` = `shipping_items`.`item_variant_id`
        INNER JOIN
    `shipments` `shipments_shipping_items` ON `shipments_shipping_items`.`id` = `shipping_items`.`shipment_id`
        INNER JOIN
    `shipment_bookings` `shipment_bookings_shipments_2` ON `shipment_bookings_shipments_2`.`id` = `shipments_shipping_items`.`shipment_booking_id`
        LEFT OUTER JOIN
    `item_families` ON `item_families`.`id` = `item_variants`.`item_family_id`
        LEFT OUTER JOIN
    `business_sites` ON `business_sites`.`id` = `shipments`.`dest_site_id`
        INNER JOIN
-- subquery starts here        
    (SELECT 
        shipments.dest_site_id,
            MAX(shipment_bookings.eta) AS max_eta,
            shipping_items.item_variant_id
    FROM
        `shipping_items`
    INNER JOIN `shipments` ON `shipments`.`id` = `shipping_items`.`shipment_id`
    INNER JOIN `shipment_bookings` ON `shipment_bookings`.`id` = `shipments`.`shipment_booking_id`
    LEFT OUTER JOIN `shipment_bookings` `shipment_bookings_shipments` ON `shipment_bookings_shipments`.`id` = `shipments`.`shipment_booking_id`
    WHERE
        `shipments`.`workflow_state` IN ('shipping' , 'unloading', 'completed', 'wrapping')
            AND ((shipments.processing_flags & 128 = 128))
            AND (`shipments`.`dest_site_id` != 1
            OR `shipments`.`dest_site_id` IS NULL)
            AND (`shipment_bookings`.`eta` > '2015-10-07')
            AND (`shipments`.`dest_site_id` IS NOT NULL)
    GROUP BY shipments.dest_site_id , `shipping_items`.`item_variant_id`) AS sub ON sub.dest_site_id = shipments_shipping_items.dest_site_id
        AND shipment_bookings_shipments_2.eta = sub.max_eta
        AND shipping_items.item_variant_id = sub.item_variant_id
-- subquery ends        
WHERE
    `item_variants`.`item_family_id` = 41
        AND `business_sites`.`selling_place_id` = 30
ORDER BY shipments_shipping_items.dest_site_id , `item_families`.`category_id` ASC , `item_families`.`brand` ASC , `item_families`.`name` ASC , `item_variants`.`variant_group_id` ASC , `item_variants`.`first_name` ASC , `item_variants`.`packaging` ASC

ruby.rb

  @shipping_items = accessible(ShippingItem).joins(shipment: :shipment_booking).
     joins(" INNER JOIN (#{subquery.to_sql}) AS sub ON sub.dest_site_id = shipments_shipping_items.dest_site_id AND shipment_bookings_shipments_2.eta = sub.max_eta AND shipping_items.item_variant_id = sub.item_variant_id")