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  1. Core Server
  2. SERVER-30480

Update aggregation explain format to provide details of merge location

    • Type: Icon: Improvement Improvement
    • Resolution: Fixed
    • Priority: Icon: Major - P3 Major - P3
    • 3.5.12
    • Affects Version/s: None
    • Component/s: Aggregation Framework
    • None
    • Fully Compatible
    • Query 2017-08-21, Query 2017-09-11

      Currently, when a sharded pipeline is explained, we expose a boolean field needsPrimaryShardMerger to indicate whether the merge part of the pipeline must be run on the database's primary shard. Given that SERVER-22760 will make it possible for mongoS to merge directly from the shards, this explain format should be updated to provide more detailed information.

      Some possible approaches include:

      • A string field mergerType which simply takes the value of mongos or mongod
      • A more detailed merger field identifying the shard or mongos which is to perform the merge. Note that in the case of a shard merge, this information may not be available at explain time.

            bernard.gorman@mongodb.com Bernard Gorman
            bernard.gorman@mongodb.com Bernard Gorman
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