The implementation queried the database for each incoming variant that
was changed. This rewrite combines ActiveRecord relations so that it
creates only one query. This saves another 5-10% of execution time when
updating enterprise fees on production instances.
When an incoming exchange of an order cycle changes, the ProductsCache
queries all affected outgoing exchanges to update them. It was creating
a big collection of exchanges with duplicates and then calling `uniq`.
That call was hitting a custom implementation of `eql?` which is very
inefficient. And since `Exchange.eql?` is ignoring the order cycle id,
it was probably filtering too many exchanges from the collection.
Fixed bug: If two order cycles sell exactly the same variants to the
same shop, the two outgoing exchanges are seen as equal. When the
variants change, ProductsCache would only update one of those two
exchanges, leaving one order cycle out of sync. This case is very rare.
It only happens if there is a shop with two active order cycles selling
exactly the same.
The new uniqueness test looks only at the attributes that are later used
to refresh the cache. I measured a page speed improvement from 90
seconds to 3 seconds (30 times faster).
The `private` modifier doesn't affect class methods. Class methods have
to be declared as private separately. Also using more guard clauses,
brackets and linebreaks.
A FeatureToggle could be switched via a class_eval in an initializer.
The initializer was installed via ofn-install. We want to get rid of
custom, untracked initializers. Here I'm changing the FeatureToggle
class to use environment variables instead.
This change needs to be followed up with a change in ofn-install to use
the new environment variable. It affects only Australian production.
This groups the Customer Totals report by variant too (among others,
including by product), and then changes the report to use the variant
SKU not the product SKU.
This adds a spec for customer totals grouping and details, which
replaces the test specific to the SKU column.
