[GitHub] [spark] peter-toth commented on a diff in pull request #40488: [SPARK-42851][SQL] Replace EquivalentExpressions with mutable map in PhysicalAggregation

["peter-toth (via GitHub)" <gi...@apache.org>]

peter-toth commented on code in PR #40488:
URL: https://github.com/apache/spark/pull/40488#discussion_r1142961725


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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala:
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@@ -296,12 +298,17 @@ object PhysicalAggregation {
       // build a set of semantically distinct aggregate expressions and re-write expressions so
       // that they reference the single copy of the aggregate function which actually gets computed.
       // Non-deterministic aggregate expressions are not deduplicated.
-      val equivalentAggregateExpressions = new EquivalentExpressions
+      val equivalentAggregateExpressions = mutable.Map.empty[Expression, Expression]
       val aggregateExpressions = resultExpressions.flatMap { expr =>
         expr.collect {
-          // addExpr() always returns false for non-deterministic expressions and do not add them.
           case a
-            if AggregateExpression.isAggregate(a) && !equivalentAggregateExpressions.addExpr(a) =>

Review Comment:
   Besides the above, although `.addExpr()` fits here well and does the job, isn't it a bit weird that an add-like method of a collection-like object doesn't return `true` when an item added, but actually it flips the meaning of the return value? If it was used at multiple places then I would keep it, but we use it only here. Maybe I'm just nitpicking...
   Anyways, I'm ok with https://github.com/apache/spark/pull/40473 too.



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