mgaido91 commented on issue #23267: [SPARK-25401] [SQL] Reorder join predicates to match child outputOrdering URL: https://github.com/apache/spark/pull/23267#issuecomment-458528158 @davidvrba my point is: is it safe to do so? I mean, are we changing the plan 2 times potentially now: the first time we reorder the keys in order to accomplish with the partitioning, the second for the orderings. So with the second change we are basically "undoing" part of the previous change, which consists of: 1. changing the order of the keys so that they match the partitioning one; 2. adding/not adding the Exchange according to the modified plan. Hence I am not sure this change you are introducing is fine in general. My understanding is that the change here is not safe in all conditions, in particular in the case when 2 re-orderings occur. If you can show that all the possible cases are safe, then it is fine, but my feeling is that it is not. Hope this more verbose comment explains more clearly what I meant. Thanks.
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