[GitHub] [spark] fqaiser94 commented on a change in pull request #27066: [SPARK-31317][SQL] Add withField method to Column

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

fqaiser94 commented on a change in pull request #27066:
URL: https://github.com/apache/spark/pull/27066#discussion_r448393694



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/complexTypeCreator.scala
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@@ -539,3 +539,79 @@ case class StringToMap(text: Expression, pairDelim: Expression, keyValueDelim: E
 
   override def prettyName: String = "str_to_map"
 }
+
+/**
+ * Adds/replaces field in struct by name.
+ */
+case class WithFields(
+    structExpr: Expression,
+    names: Seq[String],
+    valExprs: Seq[Expression]) extends Expression {
+
+  assert(names.length == valExprs.length)
+
+  override def checkInputDataTypes(): TypeCheckResult = {
+    if (!structExpr.dataType.isInstanceOf[StructType]) {
+      TypeCheckResult.TypeCheckFailure(
+        "struct argument should be struct type, got: " + structExpr.dataType.catalogString)
+    } else {
+      TypeCheckResult.TypeCheckSuccess
+    }
+  }
+
+  override def children: Seq[Expression] = structExpr +: valExprs
+
+  private lazy val addOrReplaceExprs = names.zip(valExprs)
+
+  override def dataType: StructType = {

Review comment:
       We can't do this. `evalExpr.dataType` will **always** return a nullable datatype with my most recent changes.




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