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  1. Core Server
  2. SERVER-74954

Incorrect result when contained $or rewrites $elemMatch extra condition

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    • Query Optimization
    • Minor Change
    • ALL
    • v7.0, v6.0, v5.0, v4.4
    • QO 2023-05-15, QO 2023-05-29, QO 2023-06-12, QO 2023-06-26, QO 2023-07-10
    • None
    • 3
    • None
    • None
    • None
    • None
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      Sample data:

      [
  { c: 1, p: [ { id: 1 } ] },
  { c: 2, p: [ { id: 1 } ] },
  { c: 3, p: [ { id: 1 } ] },
  { c: 4, p: [ { id: 1 } ] }
]

      Index must be present to trigger the bug: 

      { "p.id": 1, c: 1}

      Query in question:

      db.test.find(
{$and:[
      {$or:[{c:{$lt:2}},{c:{$gt:3}}]},
      {p:{$elemMatch:{id:{$eq:1,$exists:true}}}}
]}
)

      Without the index, it matches two documents. With index but without (redundant) $exists:true inside $elemMatch it also returns two documents. But with index and with redundant exists it fails to return any documents.

            Assignee:
            svilen.mihaylov@mongodb.com Svilen Mihaylov (Inactive)
            Reporter:
            asya.kamsky@mongodb.com Asya Kamsky
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            Watchers:
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              Created:
              Updated:
              Resolved: