[SPARK-11277][SQL] sort_array throws exception scala.MatchError

I'm new to spark. I was trying out the sort_array function then hit this exception. I looked into the spark source code. I found the root cause is that sort_array does not check for an array of NULLs. It's not meaningful to sort an array of entirely NULLs anyway.

I'm adding a check on the input array type to SortArray. If the array consists of NULLs entirely, there is no need to sort such array. I have also added a test case for this.

Please help to review my fix. Thanks!

Author: Jia Li <jiali@us.ibm.com>

Closes #9247 from jliwork/SPARK-11277.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala

@@ -68,6 +68,7 @@ case class SortArray(base: Expression, ascendingOrder: Expression)
   private lazy val lt: Comparator[Any] = {
     val ordering = base.dataType match {
       case _ @ ArrayType(n: AtomicType, _) => n.ordering.asInstanceOf[Ordering[Any]]
+      case _ @ ArrayType(s: StructType, _) => s.interpretedOrdering.asInstanceOf[Ordering[Any]]
     }
 
     new Comparator[Any]() {
@@ -89,6 +90,7 @@ case class SortArray(base: Expression, ascendingOrder: Expression)
   private lazy val gt: Comparator[Any] = {
     val ordering = base.dataType match {
       case _ @ ArrayType(n: AtomicType, _) => n.ordering.asInstanceOf[Ordering[Any]]
+      case _ @ ArrayType(s: StructType, _) => s.interpretedOrdering.asInstanceOf[Ordering[Any]]
     }
 
     new Comparator[Any]() {
@@ -109,7 +111,9 @@ case class SortArray(base: Expression, ascendingOrder: Expression)
   override def nullSafeEval(array: Any, ascending: Any): Any = {
     val elementType = base.dataType.asInstanceOf[ArrayType].elementType
     val data = array.asInstanceOf[ArrayData].toArray[AnyRef](elementType)
-    java.util.Arrays.sort(data, if (ascending.asInstanceOf[Boolean]) lt else gt)
+    if (elementType != NullType) {
+      java.util.Arrays.sort(data, if (ascending.asInstanceOf[Boolean]) lt else gt)
+    }
     new GenericArrayData(data.asInstanceOf[Array[Any]])
   }
 

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CollectionFunctionsSuite.scala

@@ -49,6 +49,7 @@ class CollectionFunctionsSuite extends SparkFunSuite with ExpressionEvalHelper {
     val a1 = Literal.create(Seq[Integer](), ArrayType(IntegerType))
     val a2 = Literal.create(Seq("b", "a"), ArrayType(StringType))
     val a3 = Literal.create(Seq("b", null, "a"), ArrayType(StringType))
+    val a4 = Literal.create(Seq(null, null), ArrayType(NullType))
 
     checkEvaluation(new SortArray(a0), Seq(1, 2, 3))
     checkEvaluation(new SortArray(a1), Seq[Integer]())
@@ -64,6 +65,12 @@ class CollectionFunctionsSuite extends SparkFunSuite with ExpressionEvalHelper {
     checkEvaluation(new SortArray(a3, Literal(false)), Seq("b", "a", null))
 
     checkEvaluation(Literal.create(null, ArrayType(StringType)), null)
+    checkEvaluation(new SortArray(a4), Seq(null, null))
+
+    val typeAS = ArrayType(StructType(StructField("a", IntegerType) :: Nil))
+    val arrayStruct = Literal.create(Seq(create_row(2), create_row(1)), typeAS)
+
+    checkEvaluation(new SortArray(arrayStruct), Seq(create_row(1), create_row(2)))
   }
 
   test("Array contains") {