westonpace commented on issue #35333:
URL: https://github.com/apache/arrow/issues/35333#issuecomment-1523656770

   In general, we try and avoid planning and optimization in Acero.  Building a 
full planner or optimizer is just too much work for the capacity we have.  My 
hope is that someday a Substrait planner/optimizer will emerge but we are 
probably years out from that.
   
   Now, one could make the argument that this, similar to our implicit 
conversion in expressions, is a small enough addition and not going to cause us 
to fall off the slippery slope into planning.
   
   The implicit conversion that we do already handle, which @thisisnic 
mentions, is done when we are binding expressions to a schema.  The rules there 
are actually encoded into the functions themselves (e.g. each function gets to 
decide which implicit casts are appropriate).  As a result, it isn't something 
that is easily reusable in its current form.
   
   So I guess this is kind of a non-answer to the "can we do it?" question.  I 
would say that it's doable, and if someone wanted to take this work on I would 
be willing to get it merged in.  However, it is not a priority for me 
personally at the moment.
   
   Is there any way to do the explicit cast in dplyr?  E.g. instead of making 
sure the schemas match in dplyr could you read in the data with the true schema 
and then cast id to id_64 (or id_32) right before the join?
   


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