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https://issues.apache.org/jira/browse/SPARK-25044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16573570#comment-16573570
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Lukas Rytz commented on SPARK-25044:
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This problem relates to what had to be solved for the closure cleaner. I'd be
concerned about relying on the lambda object's toString, this is not speicified
and might change in some circumstances (other JVM vendor, other release, who
knows). The only way (I know of) to get from the lambda object to the method
that implements the lambda body is to serialize the lambda and look at the
SerializedLambda. From there one could find the method that implements the
lambda body (and its declaring class). See here:
[https://docs.google.com/document/d/1fbkjEL878witxVQpOCbjlvOvadHtVjYXeB-2mgzDTvk/edit#heading=h.eq06h62nbmws.]
This is far from ideal though.. Hopefully there's a better way. I tried to see
what's available in the lambda's getClass, but coulnd't find anything.
> Address translation of LMF closure primitive args to Object in Scala 2.12
> -------------------------------------------------------------------------
>
> Key: SPARK-25044
> URL: https://issues.apache.org/jira/browse/SPARK-25044
> Project: Spark
> Issue Type: Sub-task
> Components: Spark Core, SQL
> Affects Versions: 2.4.0
> Reporter: Sean Owen
> Priority: Major
>
> A few SQL-related tests fail in Scala 2.12, such as UDFSuite's "SPARK-24891
> Fix HandleNullInputsForUDF rule":
> {code:java}
> - SPARK-24891 Fix HandleNullInputsForUDF rule *** FAILED ***
> Results do not match for query:
> ...
> == Results ==
> == Results ==
> !== Correct Answer - 3 == == Spark Answer - 3 ==
> !struct<> struct<a:bigint,b:int,c:int>
> ![0,10,null] [0,10,0]
> ![1,12,null] [1,12,1]
> ![2,14,null] [2,14,2] (QueryTest.scala:163){code}
> You can kind of get what's going on reading the test:
> {code:java}
> test("SPARK-24891 Fix HandleNullInputsForUDF rule") {
> // assume(!ClosureCleanerSuite2.supportsLMFs)
> // This test won't test what it intends to in 2.12, as lambda metafactory
> closures
> // have arg types that are not primitive, but Object
> val udf1 = udf({(x: Int, y: Int) => x + y})
> val df = spark.range(0, 3).toDF("a")
> .withColumn("b", udf1($"a", udf1($"a", lit(10))))
> .withColumn("c", udf1($"a", lit(null)))
> val plan = spark.sessionState.executePlan(df.logicalPlan).analyzed
> comparePlans(df.logicalPlan, plan)
> checkAnswer(
> df,
> Seq(
> Row(0, 10, null),
> Row(1, 12, null),
> Row(2, 14, null)))
> }{code}
>
> It seems that the closure that is fed in as a UDF changes behavior, in a way
> that primitive-type arguments are handled differently. For example an Int
> argument, when fed 'null', acts like 0.
> I'm sure it's a difference in the LMF closure and how its types are
> understood, but not exactly sure of the cause yet.
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