[SPARK-33520] make CrossValidator/TrainValidateSplit/OneVsRest Reader/Writer support Python backend estimator/evaluator

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1.0
• Fix Version/s: 3.1.0
• Component/s: ML, PySpark
• Assignee: Weichen Xu
• Reporter: Weichen Xu
• Created: 23/Nov/20 16:01
• Updated: 04/Dec/20 00:38
• Resolved: 04/Dec/20 00:38

Description

Currently, pyspark support third-party library to define python backend estimator/evaluator, i.e., estimator that inherit `Estimator` instead of `JavaEstimator`, and only can be used in pyspark.

CrossValidator and TrainValidateSplit support tuning these python backend estimator,
but cannot support saving/load, becase CrossValidator and TrainValidateSplit writer implementation is use JavaMLWriter, which require to convert nested estimator and evaluator into java instance.

OneVsRest saving/load now only support java backend classifier due to similar issue.

Issue Links

• links to: [Github] Pull Request #30471 (WeichenXu123)