With PR #34480, Tekin Suleyman added implicit_column_order for use with ordered finder methods. This support did not extend to ActiveRecord::Batches which enforces ordering on primary_key. The same logic/reasoning introduced for implicit_column_order or defining an ordering column can be extended to ordering on ActiveRecord::Batches finder methods.
Branch with my proposed changes and tests
https://github.com/rails/rails/compare/master...bullfight:imlicit_order_find_in_batches
Hey Patrick,
The use case for implicit_order_column is only intended for configuring the behaviour of finder methods where an ordering is implied, i.e. first and last, and where the default of using the primary key to order results in unpredictable behaviour, i.e. when the PK is a UUID. It wasn’t the intention that this be used as a way to define a default order on finder methods in general.
With regard to the batch finders specifically, enabling the order column to be overridden would open them up to subtle bugs and undesirable behaviour, particularly if the order column is one that isn’t guaranteed to be unique, e.g. the created_at timestamp. This could result in records being skipped or processed more than once.
Tekin