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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2022/08/05 13:06:11 UTC

[GitHub] [arrow-datafusion] andygrove opened a new issue, #3040: Follow-on work for `median` aggregate function

andygrove opened a new issue, #3040:
URL: https://github.com/apache/arrow-datafusion/issues/3040

   **Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
   Follow-on issue to address feedback in https://github.com/apache/arrow-datafusion/pull/3009
   
   In particular:
   
   - Run some performance test and see if it would be better to use builders in the aggregate state rather than arrays. Should we just use `ScalarValue::List` instead?
   - Should we have a configurable limit on the number of values that can be collected to prevent OOM?
   - Can we leverage the `concat` and `take` kernels?
   - Should we add an `average` kernel to arrow-rs?
   - Can we reduce memory overhead with some form of compression (such as run-length encoding or maintaining a map of unique values with counts)
   
   **Describe the solution you'd like**
   See above
   
   **Describe alternatives you've considered**
   None
   
   **Additional context**
   None
   


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[GitHub] [arrow-datafusion] jhorstmann commented on issue #3040: Follow-on work for `median` aggregate function

Posted by GitBox <gi...@apache.org>.
jhorstmann commented on issue #3040:
URL: https://github.com/apache/arrow-datafusion/issues/3040#issuecomment-1209471137

   Another optimization is that you do not need to to sort all values, only the value at the middle index needs to be at the right place.  [Vec::select_nth_unstable](https://doc.rust-lang.org/std/vec/struct.Vec.html#method.select_nth_unstable) does exactly that in O(n) using a quickselect algorithm.


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[GitHub] [arrow-datafusion] Dandandan commented on issue #3040: Follow-on work for `median` aggregate function

Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan commented on issue #3040:
URL: https://github.com/apache/arrow-datafusion/issues/3040#issuecomment-1689574469

   #7376 solves most of these


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[GitHub] [arrow-datafusion] Dandandan closed issue #3040: Follow-on work for `median` aggregate function

Posted by "Dandandan (via GitHub)" <gi...@apache.org>.
Dandandan closed issue #3040: Follow-on work for `median` aggregate function
URL: https://github.com/apache/arrow-datafusion/issues/3040


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