add CreateStruct

Author: mengxr

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala

@@ -212,6 +212,12 @@ class Analyzer(catalog: Catalog,
                 case o => o :: Nil
               }
               Alias(c.copy(children = expandedArgs), name)() :: Nil
+            case Alias(c @ CreateStruct(args), name) if containsStar(args) =>
+              val expandedArgs = args.flatMap {
+                case s: Star => s.expand(child.output, resolver)
+                case o => o :: Nil
+              }
+              Alias(c.copy(children = expandedArgs), name)() :: Nil
             case o => o :: Nil
           },
           child)

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

@@ -120,7 +120,7 @@ case class ArrayGetField(child: Expression, field: StructField, ordinal: Int, co
 case class CreateArray(children: Seq[Expression]) extends Expression {
   override type EvaluatedType = Any
 
-  override def foldable: Boolean = !children.exists(!_.foldable)
+  override def foldable: Boolean = children.forall(_.foldable)
 
   lazy val childTypes = children.map(_.dataType).distinct
 
@@ -142,3 +142,29 @@ case class CreateArray(children: Seq[Expression]) extends Expression {
 
   override def toString: String = s"Array(${children.mkString(",")})"
 }
+
+/**
+ * Returns a Row containing the evaluation of all children expressions.
+ */
+case class CreateStruct(children: Seq[Expression]) extends Expression {
+  override type EvaluatedType = Row
+
+  override def foldable: Boolean = children.forall(_.foldable)
+
+  override lazy val resolved: Boolean = childrenResolved
+
+  override def dataType: StructType = {
+    assert(resolved, s"CreateStruct is called with unresolved children: $children.")
+    val fields = children.map {
+      case named: NamedExpression =>
+        StructField(named.name, named.dataType, named.nullable, named.metadata)
+    }
+    StructType(fields)
+  }
+
+  override def nullable: Boolean = false
+
+  override def eval(input: Row): EvaluatedType = {
+    Row(children.map(_.eval(input)): _*)
+  }
+}

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

@@ -1080,4 +1080,11 @@ class ExpressionEvaluationSuite extends FunSuite {
     checkEvaluation(c1 ^ c2, 3, row)
     checkEvaluation(~c1, -2, row)
   }
+
+  test("CreateStruct") {
+    val row = Row(1, 2, 3)
+    val c1 = 'a.int.at(0)
+    val c3 = 'a.int.at(2)
+    checkEvaluation(CreateStruct(Seq(c1, c3)), Row(1, 3), row)
+  }
 }