[SPARK-8658][SQL][FOLLOW-UP] AttributeReference's equals method compares all the members

Based on the comment of cloud-fan in https://github.com/apache/spark/pull/9216, update the AttributeReference's hashCode function by including the hashCode of the other attributes including name, nullable and qualifiers.

Here, I am not 100% sure if we should include name in the hashCode calculation, since the original hashCode calculation does not include it.

marmbrus cloud-fan Please review if the changes are good.

Author: gatorsmile <gatorsmile@gmail.com>

Closes #9761 from gatorsmile/hashCodeNamedExpression.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala

@@ -212,9 +212,12 @@ case class AttributeReference(
   override def hashCode: Int = {
     // See http://stackoverflow.com/questions/113511/hash-code-implementation
     var h = 17
-    h = h * 37 + exprId.hashCode()
+    h = h * 37 + name.hashCode()
     h = h * 37 + dataType.hashCode()
+    h = h * 37 + nullable.hashCode()
     h = h * 37 + metadata.hashCode()
+    h = h * 37 + exprId.hashCode()
+    h = h * 37 + qualifiers.hashCode()
     h
   }
 

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/SubexpressionEliminationSuite.scala

@@ -25,14 +25,18 @@ class SubexpressionEliminationSuite extends SparkFunSuite {
     val a: AttributeReference = AttributeReference("name", IntegerType)()
     val b1 = a.withName("name2").withExprId(id)
     val b2 = a.withExprId(id)
+    val b3 = a.withQualifiers("qualifierName" :: Nil)
 
     assert(b1 != b2)
     assert(a != b1)
     assert(b1.semanticEquals(b2))
     assert(!b1.semanticEquals(a))
     assert(a.hashCode != b1.hashCode)
-    assert(b1.hashCode == b2.hashCode)
+    assert(b1.hashCode != b2.hashCode)
     assert(b1.semanticHash() == b2.semanticHash())
+    assert(a != b3)
+    assert(a.hashCode != b3.hashCode)
+    assert(a.semanticEquals(b3))
   }
 
   test("Expression Equivalence - basic") {