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
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File path: core/src/main/java/org/apache/calcite/rel/RelCollationImpl.java
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@@ -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.
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