[SPARK-6429] Implement hashCode and equals together

## What changes were proposed in this pull request?

Implement some `hashCode` and `equals` together in order to enable the scalastyle.
This is a first batch, I will continue to implement them but I wanted to know your thoughts.

Author: Joan <joan@goyeau.com>

Closes #12157 from joan38/SPARK-6429-HashCode-Equals.

6 files changed, 33 insertions, 7 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/AttributeSet.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/AttributeSet.scala
index 8bdf9b29c9..b77f93373e 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/AttributeSet.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/AttributeSet.scala
@@ -60,6 +60,8 @@ object AttributeSet {
 class AttributeSet private (val baseSet: Set[AttributeEquals])
   extends Traversable[Attribute] with Serializable {
 
+  override def hashCode: Int = baseSet.hashCode()
+
   /** Returns true if the members of this AttributeSet and other are the same. */
   override def equals(other: Any): Boolean = other match {
     case otherSet: AttributeSet =>
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
index 607c7c877c..d0ad7a05a0 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
@@ -35,7 +35,8 @@ class EquivalentExpressions {
       case other: Expr => e.semanticEquals(other.e)
       case _ => false
     }
-    override val hashCode: Int = e.semanticHash()
+
+    override def hashCode: Int = e.semanticHash()
   }
 
   // For each expression, the set of equivalent expressions.
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
index e9dda588de..7e3683e482 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
@@ -19,6 +19,7 @@ package org.apache.spark.sql.catalyst.expressions
 
 import java.nio.charset.StandardCharsets
 import java.sql.{Date, Timestamp}
+import java.util.Objects
 
 import org.json4s.JsonAST._
 
@@ -170,6 +171,8 @@ case class Literal protected (value: Any, dataType: DataType)
 
   override def toString: String = if (value != null) value.toString else "null"
 
+  override def hashCode(): Int = 31 * (31 * Objects.hashCode(dataType)) + Objects.hashCode(value)
+
   override def equals(other: Any): Boolean = other match {
     case o: Literal =>
       dataType.equals(o.dataType) &&
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
index c083f12724..8b38838537 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql.catalyst.expressions
 
-import java.util.UUID
+import java.util.{Objects, UUID}
 
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute
@@ -175,6 +175,11 @@ case class Alias(child: Expression, name: String)(
     exprId :: qualifier :: explicitMetadata :: isGenerated :: Nil
   }
 
+  override def hashCode(): Int = {
+    val state = Seq(name, exprId, child, qualifier, explicitMetadata)
+    state.map(Objects.hashCode).foldLeft(0)((a, b) => 31 * a + b)
+  }
+
   override def equals(other: Any): Boolean = other match {
     case a: Alias =>
       name == a.name && exprId == a.exprId && child == a.child && qualifier == a.qualifier &&
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/types/UserDefinedType.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/types/UserDefinedType.scala
index fb7251d71b..71a9b9f808 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/types/UserDefinedType.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/types/UserDefinedType.scala
@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql.types
 
+import java.util.Objects
+
 import org.json4s.JsonAST.JValue
 import org.json4s.JsonDSL._
 
@@ -83,6 +85,8 @@ abstract class UserDefinedType[UserType >: Null] extends DataType with Serializa
 
   override def sql: String = sqlType.sql
 
+  override def hashCode(): Int = getClass.hashCode()
+
   override def equals(other: Any): Boolean = other match {
     case that: UserDefinedType[_] => this.acceptsType(that)
     case _ => false
@@ -115,7 +119,9 @@ private[sql] class PythonUserDefinedType(
   }
 
   override def equals(other: Any): Boolean = other match {
-    case that: PythonUserDefinedType => this.pyUDT.equals(that.pyUDT)
+    case that: PythonUserDefinedType => pyUDT == that.pyUDT
     case _ => false
   }
+
+  override def hashCode(): Int = Objects.hashCode(pyUDT)
 }
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
index 18752014ea..c3b20e2cc0 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
@@ -35,6 +35,9 @@ import org.apache.spark.sql.types.{ArrayType, Decimal, ObjectType, StructType}
 case class RepeatedStruct(s: Seq[PrimitiveData])
 
 case class NestedArray(a: Array[Array[Int]]) {
+  override def hashCode(): Int =
+    java.util.Arrays.deepHashCode(a.asInstanceOf[Array[AnyRef]])
+
   override def equals(other: Any): Boolean = other match {
     case NestedArray(otherArray) =>
       java.util.Arrays.deepEquals(
@@ -64,15 +67,21 @@ case class SpecificCollection(l: List[Int])
 
 /** For testing Kryo serialization based encoder. */
 class KryoSerializable(val value: Int) {
-  override def equals(other: Any): Boolean = {
-    this.value == other.asInstanceOf[KryoSerializable].value
+  override def hashCode(): Int = value
+
+  override def equals(other: Any): Boolean = other match {
+    case that: KryoSerializable => this.value == that.value
+    case _ => false
   }
 }
 
 /** For testing Java serialization based encoder. */
 class JavaSerializable(val value: Int) extends Serializable {
-  override def equals(other: Any): Boolean = {
-    this.value == other.asInstanceOf[JavaSerializable].value
+  override def hashCode(): Int = value
+
+  override def equals(other: Any): Boolean = other match {
+    case that: JavaSerializable => this.value == that.value
+    case _ => false
   }
 }