diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/json/JsonExpressionEvalUtils.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/json/JsonExpressionEvalUtils.scala
index d0a8a3b44d299..33e430ed730f1 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/json/JsonExpressionEvalUtils.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/json/JsonExpressionEvalUtils.scala
@@ -169,38 +169,38 @@ case class SchemaOfJsonEvaluator(options: Map[String, String]) {
 /**
  * The expression `JsonTuple` will utilize it to support codegen.
  */
-case class JsonTupleEvaluator(foldableFields: IndexedSeq[Option[String]]) {
+case class JsonTupleEvaluator(foldableFieldNames: Array[Option[String]]) {
 
   import SharedFactory._
 
   // If processing fails this shared value will be returned.
   @transient private lazy val nullRow: Seq[InternalRow] =
-    new GenericInternalRow(Array.ofDim[Any](foldableFields.length)) :: Nil
+    new GenericInternalRow(Array.ofDim[Any](foldableFieldNames.length)) :: Nil
 
   // And count the number of foldable fields, we'll use this later to optimize evaluation.
-  @transient private lazy val constantFields: Int = foldableFields.count(_ != null)
+  @transient private lazy val constantFields: Int = foldableFieldNames.count(_ != null)
 
-  private def getCachedFields(fields: Seq[UTF8String]): Seq[String] = {
+  private def getFieldNameStrings(fields: Array[UTF8String]): Array[String] = {
     // Evaluate the field names as String rather than UTF8String to
     // optimize lookups from the json token, which is also a String.
     if (constantFields == fields.length) {
       // Typically the user will provide the field names as foldable expressions
       // so we can use the cached copy.
-      foldableFields.map(_.orNull)
+      foldableFieldNames.map(_.orNull)
     } else if (constantFields == 0) {
       // None are foldable so all field names need to be evaluated from the input row.
       fields.map { f => Option(f.toString).orNull }
     } else {
       // If there is a mix of constant and non-constant expressions
       // prefer the cached copy when available.
-      foldableFields.zip(fields).map {
+      foldableFieldNames.zip(fields).map {
         case (null, f) => Option(f.toString).orNull
         case (fieldName, _) => fieldName.orNull
       }
     }
   }
 
-  private def parseRow(parser: JsonParser, fieldNames: Seq[String]): Seq[InternalRow] = {
+  private def parseRow(parser: JsonParser, fieldNames: Array[String]): Seq[InternalRow] = {
     // Only objects are supported.
     if (parser.nextToken() != JsonToken.START_OBJECT) return nullRow
 
@@ -265,13 +265,13 @@ case class JsonTupleEvaluator(foldableFields: IndexedSeq[Option[String]]) {
     }
   }
 
-  final def evaluate(json: UTF8String, fields: Seq[UTF8String]): Seq[InternalRow] = {
+  final def evaluate(json: UTF8String, fieldNames: Array[UTF8String]): Seq[InternalRow] = {
     if (json == null) return nullRow
     try {
       /* We know the bytes are UTF-8 encoded. Pass a Reader to avoid having Jackson
       detect character encoding which could fail for some malformed strings. */
       Utils.tryWithResource(CreateJacksonParser.utf8String(jsonFactory, json)) { parser =>
-        parseRow(parser, getCachedFields(fields))
+        parseRow(parser, getFieldNameStrings(fieldNames))
       }
     } catch {
       case _: JsonProcessingException => nullRow
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
index 36e5710e7b1e8..8728a7333181d 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
@@ -19,7 +19,6 @@ package org.apache.spark.sql.catalyst.expressions
 
 import java.io._
 
-import scala.collection.immutable.ArraySeq
 import scala.util.parsing.combinator.RegexParsers
 
 import com.fasterxml.jackson.core._
@@ -463,11 +462,11 @@ case class JsonTuple(children: Seq[Expression])
   @transient private lazy val fieldExpressions: Seq[Expression] = children.tail
 
   // Eagerly evaluate any foldable the field names.
-  @transient private lazy val foldableFieldNames: IndexedSeq[Option[String]] = {
+  @transient private lazy val foldableFieldNames: Array[Option[String]] = {
     fieldExpressions.map {
       case expr if expr.foldable => Option(expr.eval()).map(_.asInstanceOf[UTF8String].toString)
       case _ => null
-    }.toIndexedSeq
+    }.toArray
   }
 
   override def elementSchema: StructType = StructType(fieldExpressions.zipWithIndex.map {
@@ -498,17 +497,16 @@ case class JsonTuple(children: Seq[Expression])
 
   override def eval(input: InternalRow): IterableOnce[InternalRow] = {
     val json = jsonExpr.eval(input).asInstanceOf[UTF8String]
-    val fields = fieldExpressions.map(_.eval(input).asInstanceOf[UTF8String])
-    evaluator.evaluate(json, fields)
+    val filedNames = fieldExpressions.map(_.eval(input).asInstanceOf[UTF8String]).toArray
+    evaluator.evaluate(json, filedNames)
   }
 
   override protected def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
     val refEvaluator = ctx.addReferenceObj("evaluator", evaluator)
     val jsonTerm = ctx.freshName("json")
     val jsonEval = jsonExpr.genCode(ctx)
-    val fieldsTerm = ctx.freshName("fields")
-    val fieldsEval = fieldExpressions.map(_.genCode(ctx))
-    val arraySeqClass = classOf[ArraySeq[_]].getName
+    val filedNamesTerm = ctx.freshName("fieldNames")
+    val fieldNamesEval = fieldExpressions.map(_.genCode(ctx))
     val wrapperClass = classOf[IterableOnce[_]].getName
     val setJson =
       s"""
@@ -518,27 +516,27 @@ case class JsonTuple(children: Seq[Expression])
          |  $jsonTerm = ${jsonEval.value};
          |}
          |""".stripMargin
-    val setFields = fieldsEval.zipWithIndex.map {
-      case (fieldEval, idx) =>
+    val setFieldNames = fieldNamesEval.zipWithIndex.map {
+      case (fieldNameEval, idx) =>
         s"""
-           |if (${fieldEval.isNull}) {
-           |  $fieldsTerm[$idx] = null;
+           |if (${fieldNameEval.isNull}) {
+           |  $filedNamesTerm[$idx] = null;
            |} else {
-           |  $fieldsTerm[$idx] = ${fieldEval.value};
+           |  $filedNamesTerm[$idx] = ${fieldNameEval.value};
            |}
            |""".stripMargin
     }
     ev.copy(code =
       code"""
          |UTF8String $jsonTerm = null;
-         |UTF8String[] $fieldsTerm = new UTF8String[${fieldExpressions.length - 1}];
+         |UTF8String[] $filedNamesTerm = new UTF8String[${fieldExpressions.length}];
          |${jsonEval.code}
-         |${fieldsEval.map(_.code).mkString("\n")}
+         |${fieldNamesEval.map(_.code).mkString("\n")}
          |$setJson
-         |${setFields.mkString("\n")}
+         |${setFieldNames.mkString("\n")}
          |boolean ${ev.isNull} = false;
          |$wrapperClass<InternalRow> ${ev.value} =
-         |  $refEvaluator.evaluate($jsonTerm, new $arraySeqClass.ofRef($fieldsTerm));
+         |  $refEvaluator.evaluate($jsonTerm, $filedNamesTerm);
          |""".stripMargin)
   }