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  1. Core Server
  2. SERVER-13748

Global Lock in Reduce Phase of Map/Reduce

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    Details

    • Type: Question
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Duplicate
    • Affects Version/s: 2.4.9, 2.6.0
    • Fix Version/s: None
    • Component/s: MapReduce
    • Labels:
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      Description

      When writing results to an output collection, the map/reduce engine acquires a global write lock, effectively blocking the server for all other operations. Even when the nonAtomic option is used, the global lock is acquired for every single document that is written, and since this happens pre-emptively, the effect is very much the same.

      This effectively prevents any kind of concurrency while doing map/reduce computations and should therefore be changed.

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                  Updated:
                  Resolved: