Lookup sub-pipeline is not using index for equality match

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    • Type: Bug
    • Resolution: Done
    • Priority: Major - P3
    • 3.6.3, 3.7.1
    • Affects Version/s: None
    • Component/s: Aggregation Framework
    • None
    • Environment:
      MongoDB server version: 3.6.0-rc1
    • Fully Compatible
    • ALL
    • v3.6
    • Query 2017-11-13, Query 2017-12-04, Query 2017-12-18, Query 2018-01-01, Query 2018-01-15
    • 0
    • None
    • 3
    • None
    • None
    • None
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      I am doing following aggregation to join two collection using foreign pipeline.
      It seems match stage is not using index at all.

      db.blogpost.aggregate([
  { $lookup: { 
    from: 'comment', 
    let: { blogpost_id: "$_id" }, 
    pipeline: [ { 
       $match: { $expr: { $eq: [ "$blogpost.id", "$$blogpost_id"] } } 
    } ], 
    as: 'comments'
  }}
])

            Assignee:
            David Storch
            Reporter:
            Naveen
            Votes:
            4 Vote for this issue
            Watchers:
            18 Start watching this issue

              Created:
              Updated:
              Resolved: