[jira] [Created] (SPARK-17025) Cannot persist PySpark ML Pipeline model that includes custom Transformer

["Nicholas Chammas (JIRA)" <ji...@apache.org>]

Nicholas Chammas created SPARK-17025:
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             Summary: Cannot persist PySpark ML Pipeline model that includes custom Transformer
                 Key: SPARK-17025
                 URL: https://issues.apache.org/jira/browse/SPARK-17025
             Project: Spark
          Issue Type: Bug
          Components: ML, PySpark
    Affects Versions: 2.0.0
            Reporter: Nicholas Chammas
            Priority: Minor


Following the example in [this Databricks blog post|https://databricks.com/blog/2016/05/31/apache-spark-2-0-preview-machine-learning-model-persistence.html] under "Python tuning", I'm trying to save an ML Pipeline model.

This pipeline, however, includes a custom transformer. When I try to save the model, the operation fails because the custom transformer doesn't have a {{_to_java}} attribute.

{code}
Traceback (most recent call last):
  File ".../file.py", line 56, in <module>
    model.bestModel.save('model')
  File "/usr/local/Cellar/apache-spark/2.0.0/libexec/python/lib/pyspark.zip/pyspark/ml/pipeline.py", line 222, in save
  File "/usr/local/Cellar/apache-spark/2.0.0/libexec/python/lib/pyspark.zip/pyspark/ml/pipeline.py", line 217, in write
  File "/usr/local/Cellar/apache-spark/2.0.0/libexec/python/lib/pyspark.zip/pyspark/ml/util.py", line 93, in __init__
  File "/usr/local/Cellar/apache-spark/2.0.0/libexec/python/lib/pyspark.zip/pyspark/ml/pipeline.py", line 254, in _to_java
AttributeError: 'PeoplePairFeaturizer' object has no attribute '_to_java'
{code}

Looking at the source code for [ml/base.py|https://github.com/apache/spark/blob/acaf2a81ad5238fd1bc81e7be2c328f40c07e755/python/pyspark/ml/base.py], I see that not even the base Transformer class has such an attribute.

I'm assuming this is missing functionality that is intended to be patched up (i.e. [like this|https://github.com/apache/spark/blob/acaf2a81ad5238fd1bc81e7be2c328f40c07e755/python/pyspark/ml/classification.py#L1421-L1433]).

I'm not sure if there is an existing JIRA for this (my searches didn't turn up clear results).



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