Checksum ordered by update

[ericaporter]

Not all entity tables have updated_at columns.

It is necessary to have fallback columns to order by. This PR allows the checksum lookup to be ordered by updated_at then created_at and finally the ID if the other two don't exist.

[asatwal]

In the perform method in the entities loop we should have something like:

next unless id_column_exists_for_entity?(entity)

Then we should save the order_column within the loop and pass this to build_event_for, so that we can save the order_column in the entity_check event.

[asatwal]

I think we should make a method for checking existence of id column and call this from the perform method loop.

def id_column_exists_for_entity?(entity)
  return true if ActiveRecord::Base.connection.column_exists?(entity, :id)

  Rails.logger.info("DfE::Analytics: Entity checksum: ID column missing in #{entity} - Skipping checks")

  false
end

[ericaporter]

Good plan, updates made. Ready for another review - so much complexity in this job now!

[asatwal]

👍 Looks goods.

I know it's a pain, but at some point we should have tests for tables without updated_at, without created_at also and without timestamps and id. OK for now though to get this moving.

[ericaporter]

👍 Looks goods.

I know it's a pain, but at some point we should have tests for tables without updated_at, without created_at also and without timestamps and id. OK for now though to get this moving.

@asatwal Yeah that would be sensible. I'll work on that whilst it is still fresh (today) but maybe get this one deployed so that we can test it on Apply if that sounds reasonable？