Add $merge stage to write output to existing collection

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    • Type: New Feature
    • Resolution: Fixed
    • Priority: Major - P3
    • 4.1.11
    • Affects Version/s: None
    • Component/s: Aggregation Framework
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    • Fully Compatible
    • Query 2019-04-22, Query 2019-05-06
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      This stage replaces the new modes of $out.

      The syntax is:

      {$merge: {
  into: "collection name" OR {db: "db name", coll: "collection name"},
  on: <fields used to uniquely identify a document>,
  let: <optional, variables to be in scope for pipeline below>,
  whenMatched: "replace|keepExisting|fail|merge|pipeline",
  whenNotMatched: "insert|discard|fail"
}}

      This ticket tracks support for the combination of modes already supported by $out:
      mode "insertDocuments":

      {$merge: {
  into: "x",
  on: "x_id"
  whenMatched: "fail",
  whenNotMatched: "insert"
}}

      mode "replaceDocuments":

      {$merge: {
  into: "x",
  on: "x_id"
  whenMatched: "replaceWithNew",
  whenNotMatched: "insert"
}}

      Support for other modes is tracked in their own tickets.

            Assignee:
            Anton Korshunov
            Reporter:
            Charlie Swanson
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              Created:
              Updated:
              Resolved: