Does this need to be called within a transaction? Or just an `-inDatabase` block? The doc comment needs clarifying if it doesn't need to be called within a transaction.

If it must be called within a transaction, consider using the `...inTransaction:rollback:` pattern, as here:
https://github.com/cloudant/CDTDatastore/blob/master/Classes/common/CDTDatastore.m#L390-L395