diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/RowBasedHashMapGenerator.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/RowBasedHashMapGenerator.scala
index d5508275c4..ca59bb145f 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/RowBasedHashMapGenerator.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/RowBasedHashMapGenerator.scala
@@ -44,31 +44,8 @@ class RowBasedHashMapGenerator(
     groupingKeySchema, bufferSchema) {
 
   override protected def initializeAggregateHashMap(): String = {
-    val generatedKeySchema: String =
-      s"new org.apache.spark.sql.types.StructType()" +
-        groupingKeySchema.map { key =>
-          val keyName = ctx.addReferenceObj("keyName", key.name)
-          key.dataType match {
-            case d: DecimalType =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.createDecimalType(
-                  |${d.precision}, ${d.scale}))""".stripMargin
-            case _ =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.${key.dataType})"""
-          }
-        }.mkString("\n").concat(";")
-
-    val generatedValueSchema: String =
-      s"new org.apache.spark.sql.types.StructType()" +
-        bufferSchema.map { key =>
-          val keyName = ctx.addReferenceObj("keyName", key.name)
-          key.dataType match {
-            case d: DecimalType =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.createDecimalType(
-                  |${d.precision}, ${d.scale}))""".stripMargin
-            case _ =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.${key.dataType})"""
-          }
-        }.mkString("\n").concat(";")
+    val keySchema = ctx.addReferenceObj("keySchemaTerm", groupingKeySchema)
+    val valueSchema = ctx.addReferenceObj("valueSchemaTerm", bufferSchema)
 
     s"""
        |  private org.apache.spark.sql.catalyst.expressions.RowBasedKeyValueBatch batch;
@@ -78,8 +55,6 @@ class RowBasedHashMapGenerator(
        |  private int numBuckets = (int) (capacity / loadFactor);
        |  private int maxSteps = 2;
        |  private int numRows = 0;
-       |  private org.apache.spark.sql.types.StructType keySchema = $generatedKeySchema
-       |  private org.apache.spark.sql.types.StructType valueSchema = $generatedValueSchema
        |  private Object emptyVBase;
        |  private long emptyVOff;
        |  private int emptyVLen;
@@ -90,9 +65,9 @@ class RowBasedHashMapGenerator(
        |    org.apache.spark.memory.TaskMemoryManager taskMemoryManager,
        |    InternalRow emptyAggregationBuffer) {
        |    batch = org.apache.spark.sql.catalyst.expressions.RowBasedKeyValueBatch
-       |      .allocate(keySchema, valueSchema, taskMemoryManager, capacity);
+       |      .allocate($keySchema, $valueSchema, taskMemoryManager, capacity);
        |
-       |    final UnsafeProjection valueProjection = UnsafeProjection.create(valueSchema);
+       |    final UnsafeProjection valueProjection = UnsafeProjection.create($valueSchema);
        |    final byte[] emptyBuffer = valueProjection.apply(emptyAggregationBuffer).getBytes();
        |
        |    emptyVBase = emptyBuffer;
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/VectorizedHashMapGenerator.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/VectorizedHashMapGenerator.scala
index 7b3580cecc..95ebefed08 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/VectorizedHashMapGenerator.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/VectorizedHashMapGenerator.scala
@@ -52,31 +52,9 @@ class VectorizedHashMapGenerator(
     groupingKeySchema, bufferSchema) {
 
   override protected def initializeAggregateHashMap(): String = {
-    val generatedSchema: String =
-      s"new org.apache.spark.sql.types.StructType()" +
-        (groupingKeySchema ++ bufferSchema).map { key =>
-          val keyName = ctx.addReferenceObj("keyName", key.name)
-          key.dataType match {
-            case d: DecimalType =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.createDecimalType(
-                  |${d.precision}, ${d.scale}))""".stripMargin
-            case _ =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.${key.dataType})"""
-          }
-        }.mkString("\n").concat(";")
-
-    val generatedAggBufferSchema: String =
-      s"new org.apache.spark.sql.types.StructType()" +
-        bufferSchema.map { key =>
-          val keyName = ctx.addReferenceObj("keyName", key.name)
-          key.dataType match {
-            case d: DecimalType =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.createDecimalType(
-                  |${d.precision}, ${d.scale}))""".stripMargin
-            case _ =>
-              s""".add($keyName, org.apache.spark.sql.types.DataTypes.${key.dataType})"""
-          }
-        }.mkString("\n").concat(";")
+    val schemaStructType = new StructType((groupingKeySchema ++ bufferSchema).toArray)
+    val schema = ctx.addReferenceObj("schemaTerm", schemaStructType)
+    val aggBufferSchemaFieldsLength = bufferSchema.fields.length
 
     s"""
        |  private ${classOf[OnHeapColumnVector].getName}[] vectors;
@@ -88,18 +66,15 @@ class VectorizedHashMapGenerator(
        |  private int numBuckets = (int) (capacity / loadFactor);
        |  private int maxSteps = 2;
        |  private int numRows = 0;
-       |  private org.apache.spark.sql.types.StructType schema = $generatedSchema
-       |  private org.apache.spark.sql.types.StructType aggregateBufferSchema =
-       |    $generatedAggBufferSchema
        |
        |  public $generatedClassName() {
-       |    vectors = ${classOf[OnHeapColumnVector].getName}.allocateColumns(capacity, schema);
+       |    vectors = ${classOf[OnHeapColumnVector].getName}.allocateColumns(capacity, $schema);
        |    batch = new ${classOf[ColumnarBatch].getName}(vectors);
        |
        |    // Generates a projection to return the aggregate buffer only.
        |    ${classOf[OnHeapColumnVector].getName}[] aggBufferVectors =
-       |      new ${classOf[OnHeapColumnVector].getName}[aggregateBufferSchema.fields().length];
-       |    for (int i = 0; i < aggregateBufferSchema.fields().length; i++) {
+       |      new ${classOf[OnHeapColumnVector].getName}[$aggBufferSchemaFieldsLength];
+       |    for (int i = 0; i < $aggBufferSchemaFieldsLength; i++) {
        |      aggBufferVectors[i] = vectors[i + ${groupingKeys.length}];
        |    }
        |    aggBufferRow = new ${classOf[MutableColumnarRow].getName}(aggBufferVectors);