[SPARK-20254][SQL] Remove unnecessary data conversion for Dataset with primitive array

## What changes were proposed in this pull request?

This PR elminates unnecessary data conversion, which is introduced by SPARK-19716, for Dataset with primitve array in the generated Java code.
When we run the following example program, now we get the Java code "Without this PR". In this code, lines 56-82 are unnecessary since the primitive array in ArrayData can be converted into Java primitive array by using ``toDoubleArray()`` method. ``GenericArrayData`` is not required.

```java
val ds = sparkContext.parallelize(Seq(Array(1.1, 2.2)), 1).toDS.cache
ds.count
ds.map(e => e).show
```

Without this PR
```
== Parsed Logical Plan ==
'SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#25]
+- 'MapElements <function1>, class [D, [StructField(value,ArrayType(DoubleType,false),true)], obj#24: [D
   +- 'DeserializeToObject unresolveddeserializer(unresolvedmapobjects(<function1>, getcolumnbyordinal(0, ArrayType(DoubleType,false)), None).toDoubleArray), obj#23: [D
      +- SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#2]
         +- ExternalRDD [obj#1]

== Analyzed Logical Plan ==
value: array<double>
SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#25]
+- MapElements <function1>, class [D, [StructField(value,ArrayType(DoubleType,false),true)], obj#24: [D
   +- DeserializeToObject mapobjects(MapObjects_loopValue5, MapObjects_loopIsNull5, DoubleType, assertnotnull(lambdavariable(MapObjects_loopValue5, MapObjects_loopIsNull5, DoubleType, true), - array element class: "scala.Double", - root class: "scala.Array"), value#2, None, MapObjects_builderValue5).toDoubleArray, obj#23: [D
      +- SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#2]
         +- ExternalRDD [obj#1]

== Optimized Logical Plan ==
SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#25]
+- MapElements <function1>, class [D, [StructField(value,ArrayType(DoubleType,false),true)], obj#24: [D
   +- DeserializeToObject mapobjects(MapObjects_loopValue5, MapObjects_loopIsNull5, DoubleType, assertnotnull(lambdavariable(MapObjects_loopValue5, MapObjects_loopIsNull5, DoubleType, true), - array element class: "scala.Double", - root class: "scala.Array"), value#2, None, MapObjects_builderValue5).toDoubleArray, obj#23: [D
      +- InMemoryRelation [value#2], true, 10000, StorageLevel(disk, memory, deserialized, 1 replicas)
            +- *SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#2]
               +- Scan ExternalRDDScan[obj#1]

== Physical Plan ==
*SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#25]
+- *MapElements <function1>, obj#24: [D
   +- *DeserializeToObject mapobjects(MapObjects_loopValue5, MapObjects_loopIsNull5, DoubleType, assertnotnull(lambdavariable(MapObjects_loopValue5, MapObjects_loopIsNull5, DoubleType, true), - array element class: "scala.Double", - root class: "scala.Array"), value#2, None, MapObjects_builderValue5).toDoubleArray, obj#23: [D
      +- InMemoryTableScan [value#2]
            +- InMemoryRelation [value#2], true, 10000, StorageLevel(disk, memory, deserialized, 1 replicas)
                  +- *SerializeFromObject [staticinvoke(class org.apache.spark.sql.catalyst.expressions.UnsafeArrayData, ArrayType(DoubleType,false), fromPrimitiveArray, input[0, [D, true], true) AS value#2]
                     +- Scan ExternalRDDScan[obj#1]
```

```java
/* 050 */   protected void processNext() throws java.io.IOException {
/* 051 */     while (inputadapter_input.hasNext() && !stopEarly()) {
/* 052 */       InternalRow inputadapter_row = (InternalRow) inputadapter_input.next();
/* 053 */       boolean inputadapter_isNull = inputadapter_row.isNullAt(0);
/* 054 */       ArrayData inputadapter_value = inputadapter_isNull ? null : (inputadapter_row.getArray(0));
/* 055 */
/* 056 */       ArrayData deserializetoobject_value1 = null;
/* 057 */
/* 058 */       if (!inputadapter_isNull) {
/* 059 */         int deserializetoobject_dataLength = inputadapter_value.numElements();
/* 060 */
/* 061 */         Double[] deserializetoobject_convertedArray = null;
/* 062 */         deserializetoobject_convertedArray = new Double[deserializetoobject_dataLength];
/* 063 */
/* 064 */         int deserializetoobject_loopIndex = 0;
/* 065 */         while (deserializetoobject_loopIndex < deserializetoobject_dataLength) {
/* 066 */           MapObjects_loopValue2 = (double) (inputadapter_value.getDouble(deserializetoobject_loopIndex));
/* 067 */           MapObjects_loopIsNull2 = inputadapter_value.isNullAt(deserializetoobject_loopIndex);
/* 068 */
/* 069 */           if (MapObjects_loopIsNull2) {
/* 070 */             throw new RuntimeException(((java.lang.String) references[0]));
/* 071 */           }
/* 072 */           if (false) {
/* 073 */             deserializetoobject_convertedArray[deserializetoobject_loopIndex] = null;
/* 074 */           } else {
/* 075 */             deserializetoobject_convertedArray[deserializetoobject_loopIndex] = MapObjects_loopValue2;
/* 076 */           }
/* 077 */
/* 078 */           deserializetoobject_loopIndex += 1;
/* 079 */         }
/* 080 */
/* 081 */         deserializetoobject_value1 = new org.apache.spark.sql.catalyst.util.GenericArrayData(deserializetoobject_convertedArray); /*###*/
/* 082 */       }
/* 083 */       boolean deserializetoobject_isNull = true;
/* 084 */       double[] deserializetoobject_value = null;
/* 085 */       if (!inputadapter_isNull) {
/* 086 */         deserializetoobject_isNull = false;
/* 087 */         if (!deserializetoobject_isNull) {
/* 088 */           Object deserializetoobject_funcResult = null;
/* 089 */           deserializetoobject_funcResult = deserializetoobject_value1.toDoubleArray();
/* 090 */           if (deserializetoobject_funcResult == null) {
/* 091 */             deserializetoobject_isNull = true;
/* 092 */           } else {
/* 093 */             deserializetoobject_value = (double[]) deserializetoobject_funcResult;
/* 094 */           }
/* 095 */
/* 096 */         }
/* 097 */         deserializetoobject_isNull = deserializetoobject_value == null;
/* 098 */       }
/* 099 */
/* 100 */       boolean mapelements_isNull = true;
/* 101 */       double[] mapelements_value = null;
/* 102 */       if (!false) {
/* 103 */         mapelements_resultIsNull = false;
/* 104 */
/* 105 */         if (!mapelements_resultIsNull) {
/* 106 */           mapelements_resultIsNull = deserializetoobject_isNull;
/* 107 */           mapelements_argValue = deserializetoobject_value;
/* 108 */         }
/* 109 */
/* 110 */         mapelements_isNull = mapelements_resultIsNull;
/* 111 */         if (!mapelements_isNull) {
/* 112 */           Object mapelements_funcResult = null;
/* 113 */           mapelements_funcResult = ((scala.Function1) references[1]).apply(mapelements_argValue);
/* 114 */           if (mapelements_funcResult == null) {
/* 115 */             mapelements_isNull = true;
/* 116 */           } else {
/* 117 */             mapelements_value = (double[]) mapelements_funcResult;
/* 118 */           }
/* 119 */
/* 120 */         }
/* 121 */         mapelements_isNull = mapelements_value == null;
/* 122 */       }
/* 123 */
/* 124 */       serializefromobject_resultIsNull = false;
/* 125 */
/* 126 */       if (!serializefromobject_resultIsNull) {
/* 127 */         serializefromobject_resultIsNull = mapelements_isNull;
/* 128 */         serializefromobject_argValue = mapelements_value;
/* 129 */       }
/* 130 */
/* 131 */       boolean serializefromobject_isNull = serializefromobject_resultIsNull;
/* 132 */       final ArrayData serializefromobject_value = serializefromobject_resultIsNull ? null : org.apache.spark.sql.catalyst.expressions.UnsafeArrayData.fromPrimitiveArray(serializefromobject_argValue);
/* 133 */       serializefromobject_isNull = serializefromobject_value == null;
/* 134 */       serializefromobject_holder.reset();
/* 135 */
/* 136 */       serializefromobject_rowWriter.zeroOutNullBytes();
/* 137 */
/* 138 */       if (serializefromobject_isNull) {
/* 139 */         serializefromobject_rowWriter.setNullAt(0);
/* 140 */       } else {
/* 141 */         // Remember the current cursor so that we can calculate how many bytes are
/* 142 */         // written later.
/* 143 */         final int serializefromobject_tmpCursor = serializefromobject_holder.cursor;
/* 144 */
/* 145 */         if (serializefromobject_value instanceof UnsafeArrayData) {
/* 146 */           final int serializefromobject_sizeInBytes = ((UnsafeArrayData) serializefromobject_value).getSizeInBytes();
/* 147 */           // grow the global buffer before writing data.
/* 148 */           serializefromobject_holder.grow(serializefromobject_sizeInBytes);
/* 149 */           ((UnsafeArrayData) serializefromobject_value).writeToMemory(serializefromobject_holder.buffer, serializefromobject_holder.cursor);
/* 150 */           serializefromobject_holder.cursor += serializefromobject_sizeInBytes;
/* 151 */
/* 152 */         } else {
/* 153 */           final int serializefromobject_numElements = serializefromobject_value.numElements();
/* 154 */           serializefromobject_arrayWriter.initialize(serializefromobject_holder, serializefromobject_numElements, 8);
/* 155 */
/* 156 */           for (int serializefromobject_index = 0; serializefromobject_index < serializefromobject_numElements; serializefromobject_index++) {
/* 157 */             if (serializefromobject_value.isNullAt(serializefromobject_index)) {
/* 158 */               serializefromobject_arrayWriter.setNullDouble(serializefromobject_index);
/* 159 */             } else {
/* 160 */               final double serializefromobject_element = serializefromobject_value.getDouble(serializefromobject_index);
/* 161 */               serializefromobject_arrayWriter.write(serializefromobject_index, serializefromobject_element);
/* 162 */             }
/* 163 */           }
/* 164 */         }
/* 165 */
/* 166 */         serializefromobject_rowWriter.setOffsetAndSize(0, serializefromobject_tmpCursor, serializefromobject_holder.cursor - serializefromobject_tmpCursor);
/* 167 */       }
/* 168 */       serializefromobject_result.setTotalSize(serializefromobject_holder.totalSize());
/* 169 */       append(serializefromobject_result);
/* 170 */       if (shouldStop()) return;
/* 171 */     }
/* 172 */   }
```

With this PR (eliminated lines 56-62 in the above code)
```java
/* 047 */   protected void processNext() throws java.io.IOException {
/* 048 */     while (inputadapter_input.hasNext() && !stopEarly()) {
/* 049 */       InternalRow inputadapter_row = (InternalRow) inputadapter_input.next();
/* 050 */       boolean inputadapter_isNull = inputadapter_row.isNullAt(0);
/* 051 */       ArrayData inputadapter_value = inputadapter_isNull ? null : (inputadapter_row.getArray(0));
/* 052 */
/* 053 */       boolean deserializetoobject_isNull = true;
/* 054 */       double[] deserializetoobject_value = null;
/* 055 */       if (!inputadapter_isNull) {
/* 056 */         deserializetoobject_isNull = false;
/* 057 */         if (!deserializetoobject_isNull) {
/* 058 */           Object deserializetoobject_funcResult = null;
/* 059 */           deserializetoobject_funcResult = inputadapter_value.toDoubleArray();
/* 060 */           if (deserializetoobject_funcResult == null) {
/* 061 */             deserializetoobject_isNull = true;
/* 062 */           } else {
/* 063 */             deserializetoobject_value = (double[]) deserializetoobject_funcResult;
/* 064 */           }
/* 065 */
/* 066 */         }
/* 067 */         deserializetoobject_isNull = deserializetoobject_value == null;
/* 068 */       }
/* 069 */
/* 070 */       boolean mapelements_isNull = true;
/* 071 */       double[] mapelements_value = null;
/* 072 */       if (!false) {
/* 073 */         mapelements_resultIsNull = false;
/* 074 */
/* 075 */         if (!mapelements_resultIsNull) {
/* 076 */           mapelements_resultIsNull = deserializetoobject_isNull;
/* 077 */           mapelements_argValue = deserializetoobject_value;
/* 078 */         }
/* 079 */
/* 080 */         mapelements_isNull = mapelements_resultIsNull;
/* 081 */         if (!mapelements_isNull) {
/* 082 */           Object mapelements_funcResult = null;
/* 083 */           mapelements_funcResult = ((scala.Function1) references[0]).apply(mapelements_argValue);
/* 084 */           if (mapelements_funcResult == null) {
/* 085 */             mapelements_isNull = true;
/* 086 */           } else {
/* 087 */             mapelements_value = (double[]) mapelements_funcResult;
/* 088 */           }
/* 089 */
/* 090 */         }
/* 091 */         mapelements_isNull = mapelements_value == null;
/* 092 */       }
/* 093 */
/* 094 */       serializefromobject_resultIsNull = false;
/* 095 */
/* 096 */       if (!serializefromobject_resultIsNull) {
/* 097 */         serializefromobject_resultIsNull = mapelements_isNull;
/* 098 */         serializefromobject_argValue = mapelements_value;
/* 099 */       }
/* 100 */
/* 101 */       boolean serializefromobject_isNull = serializefromobject_resultIsNull;
/* 102 */       final ArrayData serializefromobject_value = serializefromobject_resultIsNull ? null : org.apache.spark.sql.catalyst.expressions.UnsafeArrayData.fromPrimitiveArray(serializefromobject_argValue);
/* 103 */       serializefromobject_isNull = serializefromobject_value == null;
/* 104 */       serializefromobject_holder.reset();
/* 105 */
/* 106 */       serializefromobject_rowWriter.zeroOutNullBytes();
/* 107 */
/* 108 */       if (serializefromobject_isNull) {
/* 109 */         serializefromobject_rowWriter.setNullAt(0);
/* 110 */       } else {
/* 111 */         // Remember the current cursor so that we can calculate how many bytes are
/* 112 */         // written later.
/* 113 */         final int serializefromobject_tmpCursor = serializefromobject_holder.cursor;
/* 114 */
/* 115 */         if (serializefromobject_value instanceof UnsafeArrayData) {
/* 116 */           final int serializefromobject_sizeInBytes = ((UnsafeArrayData) serializefromobject_value).getSizeInBytes();
/* 117 */           // grow the global buffer before writing data.
/* 118 */           serializefromobject_holder.grow(serializefromobject_sizeInBytes);
/* 119 */           ((UnsafeArrayData) serializefromobject_value).writeToMemory(serializefromobject_holder.buffer, serializefromobject_holder.cursor);
/* 120 */           serializefromobject_holder.cursor += serializefromobject_sizeInBytes;
/* 121 */
/* 122 */         } else {
/* 123 */           final int serializefromobject_numElements = serializefromobject_value.numElements();
/* 124 */           serializefromobject_arrayWriter.initialize(serializefromobject_holder, serializefromobject_numElements, 8);
/* 125 */
/* 126 */           for (int serializefromobject_index = 0; serializefromobject_index < serializefromobject_numElements; serializefromobject_index++) {
/* 127 */             if (serializefromobject_value.isNullAt(serializefromobject_index)) {
/* 128 */               serializefromobject_arrayWriter.setNullDouble(serializefromobject_index);
/* 129 */             } else {
/* 130 */               final double serializefromobject_element = serializefromobject_value.getDouble(serializefromobject_index);
/* 131 */               serializefromobject_arrayWriter.write(serializefromobject_index, serializefromobject_element);
/* 132 */             }
/* 133 */           }
/* 134 */         }
/* 135 */
/* 136 */         serializefromobject_rowWriter.setOffsetAndSize(0, serializefromobject_tmpCursor, serializefromobject_holder.cursor - serializefromobject_tmpCursor);
/* 137 */       }
/* 138 */       serializefromobject_result.setTotalSize(serializefromobject_holder.totalSize());
/* 139 */       append(serializefromobject_result);
/* 140 */       if (shouldStop()) return;
/* 141 */     }
/* 142 */   }
```

## How was this patch tested?

Add test suites into `DatasetPrimitiveSuite`

Author: Kazuaki Ishizaki <ishizaki@jp.ibm.com>

Closes #17568 from kiszk/SPARK-20254.

6 files changed, 86 insertions, 4 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
index 9816b33ae8..d9f36f7f87 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
@@ -2230,8 +2230,8 @@ class Analyzer(
           val result = resolved transformDown {
             case UnresolvedMapObjects(func, inputData, cls) if inputData.resolved =>
               inputData.dataType match {
-                case ArrayType(et, _) =>
-                  val expr = MapObjects(func, inputData, et, cls) transformUp {
+                case ArrayType(et, cn) =>
+                  val expr = MapObjects(func, inputData, et, cn, cls) transformUp {
                     case UnresolvedExtractValue(child, fieldName) if child.resolved =>
                       ExtractValue(child, fieldName, resolver)
                   }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala
index f446c3e4a7..1a202ecf74 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/objects/objects.scala
@@ -451,6 +451,8 @@ object MapObjects {
    * @param function The function applied on the collection elements.
    * @param inputData An expression that when evaluated returns a collection object.
    * @param elementType The data type of elements in the collection.
+   * @param elementNullable When false, indicating elements in the collection are always
+   *                        non-null value.
    * @param customCollectionCls Class of the resulting collection (returning ObjectType)
    *                            or None (returning ArrayType)
    */
@@ -458,11 +460,12 @@ object MapObjects {
       function: Expression => Expression,
       inputData: Expression,
       elementType: DataType,
+      elementNullable: Boolean = true,
       customCollectionCls: Option[Class[_]] = None): MapObjects = {
     val id = curId.getAndIncrement()
     val loopValue = s"MapObjects_loopValue$id"
     val loopIsNull = s"MapObjects_loopIsNull$id"
-    val loopVar = LambdaVariable(loopValue, loopIsNull, elementType)
+    val loopVar = LambdaVariable(loopValue, loopIsNull, elementType, elementNullable)
     MapObjects(
       loopValue, loopIsNull, elementType, function(loopVar), inputData, customCollectionCls)
   }
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
index d221b0611a..dd768d18e8 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
@@ -119,7 +119,8 @@ abstract class Optimizer(sessionCatalog: SessionCatalog, conf: SQLConf)
       CostBasedJoinReorder(conf)) ::
     Batch("Decimal Optimizations", fixedPoint,
       DecimalAggregates(conf)) ::
-    Batch("Typed Filter Optimization", fixedPoint,
+    Batch("Object Expressions Optimization", fixedPoint,
+      EliminateMapObjects,
       CombineTypedFilters) ::
     Batch("LocalRelation", fixedPoint,
       ConvertToLocalRelation,
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
index 8445ee06bd..ea2c5d241d 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
@@ -23,6 +23,7 @@ import org.apache.spark.sql.catalyst.analysis._
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.expressions.aggregate._
 import org.apache.spark.sql.catalyst.expressions.Literal.{FalseLiteral, TrueLiteral}
+import org.apache.spark.sql.catalyst.expressions.objects.AssertNotNull
 import org.apache.spark.sql.catalyst.plans._
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.rules._
@@ -368,6 +369,8 @@ case class NullPropagation(conf: SQLConf) extends Rule[LogicalPlan] {
       case EqualNullSafe(Literal(null, _), r) => IsNull(r)
       case EqualNullSafe(l, Literal(null, _)) => IsNull(l)
 
+      case AssertNotNull(c, _) if !c.nullable => c
+
       // For Coalesce, remove null literals.
       case e @ Coalesce(children) =>
         val newChildren = children.filterNot(isNullLiteral)
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala
index 257dbfac8c..8cdc6425bc 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala
@@ -19,6 +19,7 @@ package org.apache.spark.sql.catalyst.optimizer
 
 import org.apache.spark.api.java.function.FilterFunction
 import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.catalyst.expressions.objects._
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.rules._
 
@@ -96,3 +97,15 @@ object CombineTypedFilters extends Rule[LogicalPlan] {
     }
   }
 }
+
+/**
+ * Removes MapObjects when the following conditions are satisfied
+ *   1. Mapobject(... lambdavariable(..., false) ...), which means types for input and output
+ *      are primitive types with non-nullable
+ *   2. no custom collection class specified representation of data item.
+ */
+object EliminateMapObjects extends Rule[LogicalPlan] {
+  def apply(plan: LogicalPlan): LogicalPlan = plan transformAllExpressions {
+     case MapObjects(_, _, _, LambdaVariable(_, _, _, false), inputData, None) => inputData
+  }
+}
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/EliminateMapObjectsSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/EliminateMapObjectsSuite.scala
new file mode 100644
index 0000000000..d4f37e2a5e
--- /dev/null
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/EliminateMapObjectsSuite.scala
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.optimizer
+
+import org.apache.spark.sql.catalyst.dsl.expressions._
+import org.apache.spark.sql.catalyst.dsl.plans._
+import org.apache.spark.sql.catalyst.encoders.ExpressionEncoder
+import org.apache.spark.sql.catalyst.expressions.AttributeReference
+import org.apache.spark.sql.catalyst.expressions.objects.Invoke
+import org.apache.spark.sql.catalyst.plans.PlanTest
+import org.apache.spark.sql.catalyst.plans.logical.{DeserializeToObject, LocalRelation, LogicalPlan}
+import org.apache.spark.sql.catalyst.rules.RuleExecutor
+import org.apache.spark.sql.types._
+
+class EliminateMapObjectsSuite extends PlanTest {
+  object Optimize extends RuleExecutor[LogicalPlan] {
+    val batches = {
+      Batch("EliminateMapObjects", FixedPoint(50),
+        NullPropagation(conf),
+        SimplifyCasts,
+        EliminateMapObjects) :: Nil
+    }
+  }
+
+  implicit private def intArrayEncoder = ExpressionEncoder[Array[Int]]()
+  implicit private def doubleArrayEncoder = ExpressionEncoder[Array[Double]]()
+
+  test("SPARK-20254: Remove unnecessary data conversion for primitive array") {
+    val intObjType = ObjectType(classOf[Array[Int]])
+    val intInput = LocalRelation('a.array(ArrayType(IntegerType, false)))
+    val intQuery = intInput.deserialize[Array[Int]].analyze
+    val intOptimized = Optimize.execute(intQuery)
+    val intExpected = DeserializeToObject(
+      Invoke(intInput.output(0), "toIntArray", intObjType, Nil, true, false),
+      AttributeReference("obj", intObjType, true)(), intInput)
+    comparePlans(intOptimized, intExpected)
+
+    val doubleObjType = ObjectType(classOf[Array[Double]])
+    val doubleInput = LocalRelation('a.array(ArrayType(DoubleType, false)))
+    val doubleQuery = doubleInput.deserialize[Array[Double]].analyze
+    val doubleOptimized = Optimize.execute(doubleQuery)
+    val doubleExpected = DeserializeToObject(
+      Invoke(doubleInput.output(0), "toDoubleArray", doubleObjType, Nil, true, false),
+      AttributeReference("obj", doubleObjType, true)(), doubleInput)
+    comparePlans(doubleOptimized, doubleExpected)
+  }
+}