Valentin Nikotin created SPARK-23833:
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Summary: Incorrect primitive type check for input arguments of udf
Key: SPARK-23833
URL: https://issues.apache.org/jira/browse/SPARK-23833
Project: Spark
Issue Type: Bug
Components: Optimizer
Affects Versions: 2.3.0, 2.2.0
Reporter: Valentin Nikotin
There is claimed behavior for scala UDFs with primitive type arguments:
{quote}Note that if you use primitive parameters, you are not able to check if
it is null or not, and the UDF will return null for you if the primitive input
is null.
{quote}
This is initial issue - SPARK-11725
Correspondent pr -
[PR|https://github.com/apache/spark/pull/9770/commits/a8a30674ce531c9cd10107200a3f72f9539cd8f6]
The problem is that {{ScalaReflection.getParameterTypes}} doesn't work
correctly due to type erasure.
The correct check "if type is primitive" should be based on typeTag something
like this:
{code:java}
typeTag[T].tpe.typeSymbol.asClass.isPrimitive
{code}
The problem appears if we have high order functions:
{code:java}
val f = (x: Long) => x
def identity[T, U](f: T => U): T => U = (t: T) => f(t)
val udf0 = udf(f)
val udf1 = udf(identity(f))
val getNull = udf(() => null.asInstanceOf[java.lang.Long])
spark.range(5).toDF().
withColumn("udf0", udf0(getNull())).
withColumn("udf1", udf1(getNull())).
show()
spark.range(5).toDF().
withColumn("udf0", udf0(getNull())).
withColumn("udf1", udf1(getNull())).
explain()
{code}
Test execution on Spark 2.2 spark-shell:
{code:java}
scala> val f = (x: Long) => x
f: Long => Long = <function1>
scala> def identity[T, U](f: T => U): T => U = (t: T) => f(t)
identity: [T, U](f: T => U)T => U
scala> val udf0 = udf(f)
udf0: org.apache.spark.sql.expressions.UserDefinedFunction =
UserDefinedFunction(<function1>,LongType,Some(List(LongType)))
scala> val udf1 = udf(identity(f))
udf1: org.apache.spark.sql.expressions.UserDefinedFunction =
UserDefinedFunction(<function1>,LongType,Some(List(LongType)))
scala> val getNull = udf(() => null.asInstanceOf[java.lang.Long])
getNull: org.apache.spark.sql.expressions.UserDefinedFunction =
UserDefinedFunction(<function0>,LongType,Some(List()))
scala> spark.range(5).toDF().
| withColumn("udf0", udf0(getNull())).
| withColumn("udf1", udf1(getNull())).
| show()
+---+----+----+
| id|udf0|udf1|
+---+----+----+
| 0|null| 0|
| 1|null| 0|
| 2|null| 0|
| 3|null| 0|
| 4|null| 0|
+---+----+----+
scala> spark.range(5).toDF().
| withColumn("udf0", udf0(getNull())).
| withColumn("udf1", udf1(getNull())).
| explain()
== Physical Plan ==
*Project [id#19L, if (isnull(UDF())) null else UDF(UDF()) AS udf0#24L,
UDF(UDF()) AS udf1#28L]
+- *Range (0, 5, step=1, splits=6)
{code}
The typeTag information about input parameters is available in udf function but
only used to get schema, it should be added to ScalaUDF too so that we can used
it later:
{code:java}
def udf[RT: TypeTag, A1: TypeTag, A2: TypeTag](f: Function2[A1, A2, RT]):
UserDefinedFunction = {
val inputTypes = Try(ScalaReflection.schemaFor(typeTag[A1]).dataType ::
ScalaReflection.schemaFor(typeTag[A2]).dataType :: Nil).toOption
UserDefinedFunction(f, ScalaReflection.schemaFor(typeTag[RT]).dataType,
inputTypes)
}
{code}
Here is current vs desired version:
{code:java}
scala> import org.apache.spark.sql.catalyst.ScalaReflection
import org.apache.spark.sql.catalyst.ScalaReflection
scala> ScalaReflection.getParameterTypes(identity(f))
res2: Seq[Class[_]] = WrappedArray(class java.lang.Object)
scala> ScalaReflection.getParameterTypes(identity(f)).map(_.isPrimitive)
res7: Seq[Boolean] = ArrayBuffer(false)
{code}
versus
{code:java}
scala> import scala.reflect.runtime.universe.{typeTag, TypeTag}
import scala.reflect.runtime.universe.{typeTag, TypeTag}
scala> def myGetParameterTypes[T : TypeTag, U](func: T => U) = {
| typeTag[T].tpe.typeSymbol.asClass
| }
myGetParameterTypes: [T, U](func: T => U)(implicit evidence$1:
reflect.runtime.universe.TypeTag[T])reflect.runtime.universe.ClassSymbol
scala> myGetParameterTypes(f)
res3: reflect.runtime.universe.ClassSymbol = class Long
scala> myGetParameterTypes(f).isPrimitive
res4: Boolean = true
{code}
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