[jira] [Resolved] (SPARK-18884) Support Array[_] in ScalaUDF

["Hyukjin Kwon (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-18884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyukjin Kwon resolved SPARK-18884.
----------------------------------
    Resolution: Incomplete

> Support Array[_] in ScalaUDF
> ----------------------------
>
>                 Key: SPARK-18884
>                 URL: https://issues.apache.org/jira/browse/SPARK-18884
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.0.2
>            Reporter: Takeshi Yamamuro
>            Priority: Minor
>              Labels: bulk-closed
>
> Throw an exception if we use `Array[_]` in `ScalaUDF`;
> {code}
> scala> import org.apache.spark.sql.execution.debug._
> scala> Seq((0, 1)).toDF("a", "b").select(array($"a", $"b").as("ar")).write.mode("overwrite").parquet("/Users/maropu/Desktop/data/")
> scala> val df = spark.read.load("/Users/maropu/Desktop/data/")
> scala> val df = Seq((0, 1)).toDF("a", "b").select(array($"a", $"b").as("ar"))
> scala> val testArrayUdf = udf { (ar: Array[Int]) => ar.sum }
> scala> df.select(testArrayUdf($"ar")).show
> Caused by: java.lang.ClassCastException: scala.collection.mutable.WrappedArray$ofRef cannot be cast to [I
>   at $anonfun$1.apply(<console>:23)
>   at org.apache.spark.sql.catalyst.expressions.ScalaUDF$$anonfun$2.apply(ScalaUDF.scala:89)
>   at org.apache.spark.sql.catalyst.expressions.ScalaUDF$$anonfun$2.apply(ScalaUDF.scala:88)
>   at org.apache.spark.sql.catalyst.expressions.ScalaUDF.eval(ScalaUDF.scala:1069)
>   ... 99 more
> {code}
> On the other hand, the query below is passed;
> {code}
> scala> val testSeqUdf = udf { (ar: Seq[Int]) => ar.sum }
> scala> df.select(testSeqUdf($"ar")).show
> +-------+
> |UDF(ar)|
> +-------+
> |      1|
> +-------+
> {code}
> I'm not sure this behivour is an expected one. The curernt implementation querys argument types (`DataType`)　by reflection (`ScalaReflection.schemaFor`) in `sql.functions.udf`, and then creates type converters (`CatalystTypeConverters`) from the types.　`Seq[_]` and `Array[_]` are represented as `ArrayType` in `DataType` and both types are handled by using `ArrayConverter.　However, since we cannot tell a difference between both types in `DataType`, ISTM it's difficut to support the two array types　based on this current design.　One idea (of curse, it's not the best) I have is to create type converters directly from `TypeTag` in `sql.functions.udf`.　This is a prototype (https://github.com/apache/spark/compare/master...maropu:ArrayTypeUdf#diff-89643554d9757dd3e91abff1cc6096c7R740) to　support both array types in `ScalaUDF`. I'm not sure this is acceptable and welcome any suggestion.



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