akurmustafa commented on issue #15607:
URL: https://github.com/apache/datafusion/issues/15607#issuecomment-2856606085

   Thanks for pushing this feature. Currently, we don't have support for 
flexible expressions in window frames. Naive implementation of this feature 
would be `O(n^2)`. Segment tree would decrease this complexity to the 
`O(n*log(n))`. 
   
   According to me, vectorization and support for flexible expressions in 
window frames (naive implementation) are kind of orthogonal. I think, we can 
either implement support for flexible window frames with naive implementation 
or vectorization first. I also think that Segment tree is kind of non-standard 
and has benefits only for some specific use cases. Segment tree should be done 
after these 2 stages (if it will be done at some point, also these 2 stages are 
kind of preliminary to trigger the use case for Segment tree). In short 
@suibianwanwank, we can implement the feature in 
[issue15714](https://github.com/apache/datafusion/issues/15714) first 
definitely. However, we shold start with the naive implementation (where window 
frame boundaries are calculated each time using binary search) without segment 
tree. 


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