ygf11 commented on PR #5430:
URL: 
https://github.com/apache/arrow-datafusion/pull/5430#issuecomment-1449960184

   > I'm not sure whether we should make the rule ReplaceDistinctWithAggregate 
to handle the where-in/exists subquery specifically. My original thinking was 
let the rules DecorrelateWhereExists and DecorrelateWhereIn rewrite the 
subqueries to Joins and in the second pass the rule 
ReplaceDistinctWithAggregate will rewrite the Distinct to Aggregate since we 
already run those rules multiple times, so that we can keep a relatively simple 
ReplaceDistinctWithAggregate rule.
   For those expr subqueries that can not be decorrelated, we can create 
another optimization task and apply all the existing rules to them
   
   Thanks @mingmwang. One thing I care about If we rewrite distinct in second 
pass, is that we have to run the rules one more time sometimes, if it is not a 
problem, it is ok to me. 


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