[GitHub] [spark] maropu commented on a change in pull request #27066: [SPARK-31317][SQL] Add withField method to Column class

[GitBox <gi...@apache.org>]

maropu commented on a change in pull request #27066: [SPARK-31317][SQL] Add withField method to Column class
URL: https://github.com/apache/spark/pull/27066#discussion_r403000695
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/complexTypeCreator.scala
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 @@ -514,3 +514,178 @@ case class StringToMap(text: Expression, pairDelim: Expression, keyValueDelim: E
 
   override def prettyName: String = "str_to_map"
 }
+
+/**
+ * Adds/replaces fields in a struct.
+ * Returns null if struct is null.
+ * If multiple fields already exist with the one of the given fieldNames, they will all be replaced.
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+  usage = "_FUNC_(struct, name1, val1, name2, val2, ...) - Adds/replaces fields in struct by name.",
+  examples = """
+    Examples:
+      > SELECT _FUNC_(NAMED_STRUCT("a", 1), "b", 2, "c", 3);
+       {"a":1,"b":2,"c":3}
+  """)
+// scalastyle:on line.size.limit
+case class AddFields(children: Seq[Expression]) extends Expression {
+
+  private lazy val struct: Expression = children.head
+  private lazy val (nameExprs, valExprs) = children.drop(1).grouped(2).map {
+    case Seq(name, value) => (name, value)
+  }.toList.unzip
+  private lazy val fieldNames = nameExprs.map(_.eval().asInstanceOf[UTF8String].toString)
+  private lazy val pairs = fieldNames.zip(valExprs)
+
+  override def nullable: Boolean = struct.nullable
+
 
 Review comment:
   `override def foldable: Boolean = valExprs.forall(_.foldable)`?

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