asolimando commented on PR #4585:
URL: https://github.com/apache/calcite/pull/4585#issuecomment-3427599684

   > > > @asolimando I've made some adjustments. This is the best solution I 
can think of at the moment. Please take another look—your feedback is greatly 
appreciated! If you think this approach isn't suitable, we can pause for now 
and see if anyone in the JIRA thread can help brainstorm alternative solutions.
   > > 
   > > 
   > > The updated version feels like an improvement into the right direction 
already, but I was wondering if we could optimize/simplify the target collation 
and then compare as usual?
   > > For your iq query example, would it be possible to determine that `[0, 
1] => [0]` for the query as well? At that point we would just need to match as 
we used to do, but I don't know if that's feasible
   > 
   > If 0 -> 1, it can be proven that [0,1] and [0] are equivalent, so it has 
no impact on the query results. If performing only ORDER BY 0 affects the 
results, it indicates an issue with the rule implementation. Here, we only need 
to record the equivalent collection before optimization, and during trait 
satisfaction judgment, adding the [0] attribute RelSubset to the [0,1] 
attribute RelSubset will fulfill the overall requirement.
   
   What I mean is: do we need to store the original mapping if we can optimize 
the requested collation?
   
   If we could do that, we would end up with the same exact collation, we could 
just compare optimized with optimized directly without having to store the 
mapping original->optimized. Would that be possible in your opinion?


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