[SPARK-34749][SQL] Simplify ResolveCreateNamedStruct

### What changes were proposed in this pull request?

This is a follow-up of #31808 and simplifies its fix to one line (excluding comments).

### Why are the changes needed?

code simplification

### Does this PR introduce _any_ user-facing change?

no

### How was this patch tested?

N/A

Closes #31843 from cloud-fan/simplify.

Authored-by: Wenchen Fan <[email protected]>
Signed-off-by: Takeshi Yamamuro <[email protected]>

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

@@ -3973,8 +3973,6 @@ object ResolveCreateNamedStruct extends Rule[LogicalPlan] {
       val children = e.children.grouped(2).flatMap {
         case Seq(NamePlaceholder, e: NamedExpression) if e.resolved =>
           Seq(Literal(e.name), e)
-        case Seq(NamePlaceholder, e: ExtractValue) if e.resolved && e.name.isDefined =>
-          Seq(Literal(e.name.get), e)
         case kv =>
           kv
       }

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

@@ -20,7 +20,7 @@ package org.apache.spark.sql.catalyst.expressions
 import scala.collection.mutable.ArrayBuffer
 
 import org.apache.spark.sql.catalyst.InternalRow
-import org.apache.spark.sql.catalyst.analysis.{Resolver, TypeCheckResult, TypeCoercion, UnresolvedExtractValue}
+import org.apache.spark.sql.catalyst.analysis.{Resolver, TypeCheckResult, TypeCoercion, UnresolvedAttribute, UnresolvedExtractValue}
 import org.apache.spark.sql.catalyst.analysis.FunctionRegistry.{FUNC_ALIAS, FunctionBuilder}
 import org.apache.spark.sql.catalyst.expressions.codegen._
 import org.apache.spark.sql.catalyst.expressions.codegen.Block._
@@ -339,6 +339,14 @@ object CreateStruct {
    */
   def apply(children: Seq[Expression]): CreateNamedStruct = {
     CreateNamedStruct(children.zipWithIndex.flatMap {
+      // For multi-part column name like `struct(a.b.c)`, it may be resolved into:
+      //   1. Attribute if `a.b.c` is simply a qualified column name.
+      //   2. GetStructField if `a.b` refers to a struct-type column.
+      //   3. GetArrayStructFields if `a.b` refers to a array-of-struct-type column.
+      //   4. GetMapValue if `a.b` refers to a map-type column.
+      // We should always use the last part of the column name (`c` in the above example) as the
+      // alias name inside CreateNamedStruct.
+      case (u: UnresolvedAttribute, _) => Seq(Literal(u.nameParts.last), u)
       case (e: NamedExpression, _) if e.resolved => Seq(Literal(e.name), e)
       case (e: NamedExpression, _) => Seq(NamePlaceholder, e)
       case (e, index) => Seq(Literal(s"col${index + 1}"), e)

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

@@ -90,10 +90,7 @@ object ExtractValue {
   }
 }
 
-trait ExtractValue extends Expression {
-  // The name that is used to extract the value.
-  def name: Option[String]
-}
+trait ExtractValue extends Expression
 
 /**
  * Returns the value of fields in the Struct `child`.
@@ -159,7 +156,6 @@ case class GetArrayStructFields(
   override def dataType: DataType = ArrayType(field.dataType, containsNull)
   override def toString: String = s"$child.${field.name}"
   override def sql: String = s"${child.sql}.${quoteIdentifier(field.name)}"
-  override def name: Option[String] = Some(field.name)
 
   protected override def nullSafeEval(input: Any): Any = {
     val array = input.asInstanceOf[ArrayData]
@@ -237,7 +233,6 @@ case class GetArrayItem(
 
   override def toString: String = s"$child[$ordinal]"
   override def sql: String = s"${child.sql}[${ordinal.sql}]"
-  override def name: Option[String] = None
 
   override def left: Expression = child
   override def right: Expression = ordinal
@@ -453,13 +448,6 @@ case class GetMapValue(
 
   override def toString: String = s"$child[$key]"
   override def sql: String = s"${child.sql}[${key.sql}]"
-  override def name: Option[String] = key match {
-    case NonNullLiteral(s, StringType) => Some(s.toString)
-    // For GetMapValue(Attr("a"), "b") that is resolved from `a.b`, the string "b" may be casted to
-    // the map key type by type coercion rules. We can still get the name "b".
-    case Cast(NonNullLiteral(s, StringType), _, _) => Some(s.toString)
-    case _ => None
-  }
 
   override def left: Expression = child
   override def right: Expression = key

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala

@@ -425,7 +425,7 @@ class ExpressionParserSuite extends AnalysisTest {
     assertEqual("(a + b).b", ('a + 'b).getField("b")) // This will fail analysis.
     assertEqual(
       "struct(a, b).b",
-      namedStruct(NamePlaceholder, 'a, NamePlaceholder, 'b).getField("b"))
+      namedStruct(Literal("a"), 'a, Literal("b"), 'b).getField("b"))
   }
 
   test("reference") {