[GitHub] [spark] viirya commented on a diff in pull request #40662: [SPARK-43030][SQL] Deduplicate relations with metadata columns

["viirya (via GitHub)" <gi...@apache.org>]

viirya commented on code in PR #40662:
URL: https://github.com/apache/spark/pull/40662#discussion_r1158877847


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/DeduplicateRelations.scala:
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@@ -25,18 +25,12 @@ import org.apache.spark.sql.catalyst.rules.Rule
 import org.apache.spark.sql.catalyst.trees.TreePattern._
 
 /**
- * A helper class used to detect duplicate relations fast in `DeduplicateRelations`
+ * A helper class used to detect duplicate relations fast in `DeduplicateRelations`. Two relations
+ * are duplicated if:
+ *  1. they are the same class.
+ *  2. they have the same output attribute IDs.

Review Comment:
   Could two relations be of different classes but have same output attributes IDs?



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