Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/2082#discussion_r16691550
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/complexTypes.scala
---
@@ -101,3 +101,44 @@ case class GetField(child: Expression, fieldName:
String) extends UnaryExpressio
override def toString = s"$child.$fieldName"
}
+
+/**
+ * Returns the value of fields[] in the Struct `child`.
+ * for array of structs
+ */
+
+case class GetArrayField(child: Expression, fieldName: String) extends
UnaryExpression {
+ type EvaluatedType = Any
+
+ def dataType = field.dataType
+ override def nullable = child.nullable || field.nullable
+ override def foldable = child.foldable
+
+ protected def arrayType = child.dataType match {
+ case s: ArrayType => s.elementType match {
+ case t :StructType => t
+ case otherType => sys.error(s"GetArrayField is not valid on fields
of type $otherType")
+ }
+ case otherType => sys.error(s"GetArrayField is not valid on fields of
type $otherType")
+ }
+
+ lazy val field =
+ arrayType.fields
+ .find(_.name == fieldName)
+ .getOrElse(sys.error(s"No such field $fieldName in
${child.dataType}"))
+
+
+ lazy val ordinal = arrayType.fields.indexOf(field)
+
+ override lazy val resolved = childrenResolved &&
child.dataType.isInstanceOf[ArrayType]
--- End diff --
This should also check that the element type of the ArrayType is StructType
and that the requested field name can be found in that struct.
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