kasakrisz commented on code in PR #5998:
URL: https://github.com/apache/hive/pull/5998#discussion_r2257017348
##########
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/translator/PlanModifierForASTConv.java:
##########
@@ -230,6 +225,47 @@ private static void convertOpTree(RelNode rel, RelNode
parent) {
}
}
+ /**
+ * A handler that detects self-joins in the plan and rewrites them to
resolve ambiguous aliases.
+ * The handler traverses the plan and collects aliases of tables it
encounters for each join branch.
+ * When the same alias occurs in both branches of a join, it introduces a
derive table (Project)
+ * over the left branch to break the ambiguity.
+ */
+ private static class SelfJoinHandler extends RelHomogeneousShuttle {
+ private final Set<String> aliases = new HashSet<>();
+
+ @Override
+ public RelNode visit(final RelNode rel) {
+ if (rel instanceof Join join) {
Review Comment:
Can `HiveRelShuttleImpl` be used instead of `RelHomogeneousShuttle` to get
rid of `rel instanceof <Something>`?
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