[GitHub] [arrow-datafusion] alex-natzka commented on a diff in pull request #3861: Fix 3635 redundant projections

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

alex-natzka commented on code in PR #3861:
URL: https://github.com/apache/arrow-datafusion/pull/3861#discussion_r999144048


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benchmarks/expected-plans/q19.txt:
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@@ -1,9 +1,8 @@
 Projection: SUM(lineitem.l_extendedprice * Int64(1) - lineitem.l_discount) AS revenue
   Aggregate: groupBy=[[]], aggr=[[SUM(CAST(lineitem.l_extendedprice AS Decimal128(38, 4)) * CAST(Decimal128(Some(100),23,2) - CAST(lineitem.l_discount AS Decimal128(23, 2)) AS Decimal128(38, 4))) AS SUM(lineitem.l_extendedprice * Int64(1) - lineitem.l_discount)]]
-    Projection: lineitem.l_extendedprice, lineitem.l_discount

Review Comment:
   Hm, I don't think the hash aggregation takes columns into account which are neither in the `groupBy` nor in the `aggr` expressions. Even if it did, it probably shouldn't be the job of `CommonSubexprEliminate` to ensure that redundant columns are projected out first, that should be it's own (physical?) optimization rule IMO.



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