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  1. Documentation
  2. DOCS-14941

[SERVER] Investigate changes in SERVER-53771: $facet should report its summary stats

      Downstream Change Summary

      In this ticket, we've modified the explain output for aggregations using $facet. If the explain verbosity is allPlansExecution or above, we will add total aggregate execution stats for the $facet stage to the output. The specific stats are an accumulation of the stats for the sub-stages contained within the $facet, similar to how plan summary stats are shared for $unionWith.

      Description of Linked Ticket

      $facet current does not report its plan summary stats currently. The problem is similar to the work been done on $lookup, $sort, and $unionWith.

      The problem of not reporting such stats becomes more visible when $facet is present as a sub-pipeline and the top-level pipeline is been asked to report its aggregated summary stats. In this current scenario, $facet will not be able to report such stats, and hence, the top-level pipeline will also report incorrect stats.

      A client could also ask for stats directly from $facet if it is present as a top-level pipeline and this will also report incorrect stats.

      The infra for the same is already available in the current code-base where each derived document source should override the DocumentSource::getSpecificStats() method, if required. SpecificStats base class has a helper method accumulate() which is a convenient method to gather the summary stats from foreign DocumentSources.

       

      In this ticket, we should utilize the current infra and $facet should start reporting its stats.

       

            Assignee:
            Unassigned Unassigned
            Reporter:
            backlog-server-pm Backlog - Core Eng Program Management Team
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              Created:
              Updated:
              Resolved:
              49 weeks ago