[GitHub] [calcite] zabetak commented on a change in pull request #2418: [CALCITE-4621] SemiJoinRule throws AssertionError on ANTI join

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

zabetak commented on a change in pull request #2418:
URL: https://github.com/apache/calcite/pull/2418#discussion_r639730115



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File path: core/src/main/java/org/apache/calcite/rel/rules/SemiJoinRule.java
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@@ -45,8 +46,9 @@
 public abstract class SemiJoinRule
     extends RelRule<SemiJoinRule.Config>
     implements TransformationRule {
-  private static boolean notGenerateNullsOnLeft(Join join) {
-    return !join.getJoinType().generatesNullsOnLeft();
+  private static boolean isJoinTypeSupported(Join join) {
+    final JoinRelType type = join.getJoinType();
+    return type != JoinRelType.RIGHT && type != JoinRelType.FULL && type != JoinRelType.ANTI;

Review comment:
       The code could be slightly more readable (given the current name of the method) if you formulated the condition using `==` instead of `!=` operator. The equivalent of the current code would be:
   `return type == JoinRelType.INNER || type == JoinRelType.LEFT || type == JoinRelType.SEMI`
   
   Moreover, I am not sure if it is intended that you consider `SEMI` as supported join type. I was thinking that it doesn't make sense to use the rule if the join is already `SEMI` join. 




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