alamb commented on issue #24704:
URL: https://github.com/apache/datafusion/issues/24704#issuecomment-5681440427

   > Having nested Vec harm performance due to the extra indirection and add 
cost for the low cardinality case
   > instead we can implement it using mmap which complicate the implementation 
but will allow for better performance and less indirection since we will treat 
it as single flat vec.
   
   I don't fully understand what the mmap proposal is 
   
   > instead what I did is supporting in arrow sort (I've coping the original 
arrow sort code to my branch) and allow to sort across multiple blocks while 
keeping them separated.
   
   This makes sense to me (basically a sort kernel that takes `Vec<Array>` and 
returns `Vec<Array>` where the arrays are reordered.
   
   We could also look into reusing the array allocations internally 🤔 
   
   


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