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  1. Core Server
  2. SERVER-57483

Results from $lookup stage are not cached for a resharding operation's sub-pipeline

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    • Fully Compatible
    • ALL
    • v5.0
    • Sharding 2021-06-14
    • 1

    Description

      DocumentSourceLookUp::buildPipeline() calls ShardServerProcessInterface::attachCursorSourceToPipeline() which calls sharded_agg_helpers::attachCursorToPipeline() and always serializes and re-parses, even when the pipeline may execute locally on the shard via ShardServerProcessInterface::attachCursorSourceToPipelineForLocalRead().

      Because the $sequentialCache stage omits itself from the serialized pipeline, the parsed pipeline which executes locally on the shard won't ever use the cache.

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              max.hirschhorn@mongodb.com Max Hirschhorn
              max.hirschhorn@mongodb.com Max Hirschhorn
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