Create data migration for spree_orders.shipment_total

[BMorearty]

When the shipment_total column was added to spree_orders, the column was not populated in existing orders (if upgrading from an older version of Spree).

Could someone who's more familiar with the code than I am, please create a migration? Or I'll do it if you point me the right way.

Here's one way that might work:

Spree::Order.find_each { |order| OrderUpdater.new(order).update_shipment_total; order.save }

But it was suggested in IRC that a single SQL "UPDATE" statement might be possible as well, and would certainly be faster.

[huoxito]

played a while with sql today, I think something like this might fix the issue is a faster way:

UPDATE spree_orders
SET shipment_total = (SELECT SUM(spree_shipments.cost) AS sum_id
                      FROM spree_shipments
                      WHERE spree_shipments.order_id = spree_orders.id)

I'm just not sure right now if we should add a new migration or update existing ones to add that code. At this point perhaps the ideal fix would be add that sample at some upgrade guide.

[peterberkenbosch]

This is also an issue for tax adjustments btw.

[BMorearty]

I would not update the existing migration. I think it's better to add a new one.

However, because the migration is being added late, don't update shipment_total on records that already have a shipment_total. (Orders that were created in Spree 2.2). Add this to the end:

WHERE shipment_total = 0

[huoxito]

Added migration to populate that field on 2-2-stable. Still feels weird to have it there but I hope users read the migrations content before they run it in production. thanks @BMorearty