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  1. Core Server
  2. SERVER-41747

Refactor cluster aggregate planning to only attempt to split the pipeline once

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    • Icon: Improvement Improvement
    • Resolution: Unresolved
    • Icon: Major - P3 Major - P3
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    • Query Optimization
    • Query 2019-07-01

    Description

      During development on SERVER-5477 we noticed that Pipeline::requiredToRunOnMongos() emulates much of the logic in cluster_aggregation_planner::splitPipeline(). This caused problems when we wanted to add the shard key as a parameter to distributedPlanLogic(), because keeping track of what the shard key is at every stage in the pipeline is non-trivial due to renamed and modified paths at each stage. 

      After staring at this problem for a while, george.wangensteen, ted.tuckman and I think the best solution is to do a refactor to push the logic about where the pipeline is required to run down into cluster_aggregation_planner::splitPipeline() and then delete helpers on Pipeline such as requiredToRunOnMongos().

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            backlog-query-optimization Backlog - Query Optimization
            charlie.swanson@mongodb.com Charlie Swanson
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