[GitHub] [calcite] rubenada commented on a change in pull request #1814: [CALCITE-3804] Use RelCollation interface in RelCollationImpl compareTo and satisfies methods

[GitBox <gi...@apache.org>]

rubenada commented on a change in pull request #1814: [CALCITE-3804] Use RelCollation interface in RelCollationImpl compareTo and satisfies methods
URL: https://github.com/apache/calcite/pull/1814#discussion_r380761223
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rel/RelCollationImpl.java
 ##########
 @@ -97,9 +96,11 @@ public boolean isTop() {
   }
 
   public int compareTo(@Nonnull RelMultipleTrait o) {
-    final RelCollationImpl that = (RelCollationImpl) o;
-    final UnmodifiableIterator<RelFieldCollation> iterator =
-        that.fieldCollations.iterator();
+    if (this == o) {
+      return 0;
+    }
+    final RelCollation that = (RelCollation) o;
 
 Review comment:
   @zabetak, thanks for your comment. 
   There is no particular need for this change, I was just looking at this code and though that it might be "more correct" to work at interface level in these methods.
   
   I agree that comparison between classes can be risky, although we already do something like this in `RelDistributionImpl#compareTo`. But I have no problem to remove this change, your example makes clear that it can lead to risky consequences.
   
   I docthink that the change in `satisfies` is harmless. We could move it as default implementation of the `RelCollation` interface, but then I believe it would be inconsistent with other methods in implemented in `RelCollationImpl` that could be moved as default is `RelCollation` too. IMHO `RelCollationImpl` is like our de-facto default implementation of `RelCollation`, so we should put the methods implementations in there.
   
   This is a minor, cosmetic modification, so no big deal if we decide to discard some / all changes.
   

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services