Added inline comment for the canEqual PR by @cloud-fan.

1 files changed, 6 insertions, 1 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala
index 5f0592dc1d..3623fefbf2 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala
@@ -364,8 +364,13 @@ trait Row extends Serializable {
     false
   }
 
-  protected def canEqual(other: Any) =
+  protected def canEqual(other: Any) = {
+    // Note that InternalRow overrides canEqual. These two canEqual's together makes sure that
+    // comparing the external Row and InternalRow will always yield false.
+    // In the future, InternalRow should not extend Row. In that case, we can remove these
+    // canEqual methods.
     other.isInstanceOf[Row] && !other.isInstanceOf[InternalRow]
+  }
 
   override def equals(o: Any): Boolean = {
     if (o == null || !canEqual(o)) return false