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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2020/12/30 11:04:21 UTC

[GitHub] [arrow] Dandandan commented on pull request #9042: ARROW-11064: [Rust][DataFusion] Speed up hash join on smaller batches

Dandandan commented on pull request #9042:
URL: https://github.com/apache/arrow/pull/9042#issuecomment-752418069


   @jorgecarleitao Yes, small things can have a big effect...
   
   The difference is a bit "magnified" though because of the `n*n` behavior in the join.
   If you have ideas of how to solve this issue, please share.
   
   What looks like is the problem here:
   
   * for the left side of the join we  `.iter()` on the left side batches iteration (a couple of times, in the join implementation itself and in `MutableDataArray`) when we process a probe-side batch.
   * if we halve the batch size, the number of items in the build-side array grows by two, but also the number of probe-side batches we process in the join, thus the `n*n` slowdown.
   
   
   


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