Github user sun-rui commented on a diff in the pull request:
https://github.com/apache/spark/pull/12493#discussion_r60345317
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/r/MapPartitionsRWrapper.scala
---
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.r
+
+import org.apache.spark.api.r.RRunner
+import org.apache.spark.api.r.SerializationFormats
+import org.apache.spark.broadcast.Broadcast
+import org.apache.spark.sql.api.r.SQLUtils._
+import org.apache.spark.sql.types.StructType
+import org.apache.spark.sql.Row
+
+/**
+ * A function wrapper that applies the given R function to each partition.
+ */
+private[sql] case class MapPartitionsRWrapper(
--- End diff --
No. Because you can't have a serialized R function on Scala side.
But interestingly, there actually is a desired scenario mentioned several
times in the Spark mailing list that users are writing Scala/Java Spark
applications (not SparkR) but want to use R functions in some transformations.
typically this can be achieved by calling Pipe() in RDD. However, there are
limitations on pipe(). So I think in the future we can support apply a R
function in source code format to a Dataset/DataFrame (Thus SparkR is not
needed for serializing an R function.) In that case, we can have a Scala test
for it.
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