Add Sidekiq::Orm::ManagerWorker

[yelled3]

should be logic only and delegate the ORM interaction to ORM specific module.
e.g

# activerecord module
def select_models
     models = models_query.select(selected_attributes)
end
# and
def find_in_batches
     models.find_in_batches(batch_size: batch_size) do |models_batch|
end

sidekiq-orm/sidekiq-activerecord#2 (comment)

@seuros I'm not sure if find_in_batches is available in other ORMs.
need to think about it.