[GitHub] [arrow-datafusion] Dandandan commented on pull request #268: Fix wrong projection 'optimization'

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

Dandandan commented on pull request #268:
URL: https://github.com/apache/arrow-datafusion/pull/268#issuecomment-832722639


   > Nice catch! Though looks like removing the optimisation breaks a crapload of logical plan text assertions in the tests that now contain an extra top-level projection node :(
   > 
   > Could we retain the optimisation but only apply it when `expr` consists entirely of simple column refs? Not sure if that'd patch up all the tests or not.
   > 
   > Edit: or we could just modify the test assertions, I suppose, if we want to keep the initial planning process simple and do this kind of optimisation later?
   
   Thanks @returnString !
   I will have a look later. I think it would be best to update the tests instead for now.
   
   I think the optimization also doesn't improve performance that much, as the projection with just the fields should be almost "free" in DF. I will add an issue to add the optimization as a rule.


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