[GitHub] [arrow] jorgecarleitao commented on pull request #8034: ARROW-9464: [Rust] [DataFusion] Physical plan optimization rule to insert MergeExec when needed

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jorgecarleitao commented on pull request #8034:
URL: https://github.com/apache/arrow/pull/8034#issuecomment-678807425


   It looks fantastic! Super excited to see this!
   
   Gave it a quick look, and my understanding so far:
   
   * Physical nodes have requirements (`required_child_distribution`)
   * Physical nodes can fulfill requirements (`output_partitioning`)
   * The physical optimizer knows which physical nodes fulfill certain requirements (Merge fulfills `Distribution::SinglePartition` so far), and introduces them to fulfill a nodes' requirements, by using `children` to get the node's children and `with_new_children` to re-write the node with new children (that fulfill requirements).
   
   Is this a good overview of this PR (before going into the specifics)?


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