HadoopFormatIO eagerly clone key-values if they are not a well known immutable types. This make sense due to how hadoop Writables behave. However, user can use key value translation functions which possibly already output immutable types. In such case it would be of benefit if extra clone via coder can be avoided.
It would be great if coder can be consulted on the type an it's need for clone. However I am not aware if such detection is possible. I propose to add config parameter for skipping the clone which can be used by IO user.