Support limit copy in stages that absorb unwind

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    • Type: Improvement
    • Resolution: Unresolved
    • Priority: Major - P3
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    • Affects Version/s: None
    • Component/s: None
    • Query Optimization
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      In SERVER-27598 we implemented a re-write:

      ..., {$unwind: {..., preserveNullAndEmptyArrays: true}}, {$limit: X}, ...

      into

      ..., {$limit: X}, {$unwind: {..., preserveNullAndEmptyArrays: true}}, {$limit: X}, ...

      However, if $unwind is absorbed by $lookup or $graphLookup, this optimization is not performed. See repro.js

      lookup-unwind is a very popular query patter, so this should be improved.

        1. repro.js
          0.9 kB

            Assignee:
            Unassigned
            Reporter:
            Ivan Fefer
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              Created:
              Updated: