Fix equals and tests

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/ArrayBasedMapData.scala

@@ -39,17 +39,10 @@ class ArrayBasedMapData(val keyArray: ArrayData, val valueArray: ArrayData) exte
   }
 
   override def equals(obj: Any): Boolean = {
-    if (obj == null && this == null) {
-      return true
+    obj match {
+      case other: ArrayBasedMapData => keyArray == other.keyArray && valueArray == other.valueArray
+      case _ => false
     }
-
-    if (obj == null || !obj.isInstanceOf[ArrayBasedMapData]) {
-      return false
-    }
-
-    val other = obj.asInstanceOf[ArrayBasedMapData]
-
-    keyArray.equals(other.keyArray) && valueArray.equals(other.valueArray)
   }
 
   // Hash this class as a Product of two hashCodes. We don't know the DataType which prevents us

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/MapData.scala

@@ -20,9 +20,8 @@ package org.apache.spark.sql.catalyst.util
 import org.apache.spark.sql.types.DataType
 
 /**
- * This is an internal data representation for map type in Spark SQL. This should not implement
- * `equals` and `hashCode` because the type cannot be used as join keys, grouping keys, or
- * in equality tests. See SPARK-9415 and PR#13847 for the discussions.
+ * This is an internal data representation for map type in Spark SQL. This type cannot be used as
+ * join keys, grouping keys, or in equality tests. See SPARK-9415 and PR#13847 for the discussions.
  */
 abstract class MapData extends Serializable {
 

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/util/ArrayBasedMapBuilderSuite.scala

@@ -164,13 +164,11 @@ class ArrayBasedMapBuilderSuite extends SparkFunSuite with SQLHelper {
 
     // We expect two objects to be equal and to have the same hashCode if they have the same
     // elements.
-    assert(arrayBasedMapData1 == arrayBasedMapData2)
     assert(arrayBasedMapData1.equals(arrayBasedMapData2))
     assert(arrayBasedMapData1.hashCode() == arrayBasedMapData2.hashCode())
 
-    // If two objects have different elements, we expect them to not be equal and their hashCode
+    // If two objects have different elements, we expect them not to be equal and their hashCode
     // to be different.
-    assert(arrayBasedMapData1 != arrayBasedMapData3)
     assert(!arrayBasedMapData1.equals(arrayBasedMapData3))
     assert(arrayBasedMapData1.hashCode() != arrayBasedMapData3.hashCode())
   }

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/util/ComplexDataSuite.scala

@@ -39,8 +39,6 @@ class ComplexDataSuite extends SparkFunSuite {
     val testArrayMap2 = ArrayBasedMapData(testMap2.toMap)
     val testArrayMap3 = ArrayBasedMapData(testMap3.toMap)
     val testArrayMap4 = ArrayBasedMapData(testMap4.toMap)
-    assert(testArrayMap1 !== testArrayMap3)
-    assert(testArrayMap2 !== testArrayMap4)
 
     // UnsafeMapData
     val unsafeConverter = UnsafeProjection.create(Array[DataType](MapType(StringType, IntegerType)))