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  1. Core Server
  2. SERVER-37182

Different values when referencing whole object vs. a field of that object after $arrayToObject

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    • Minor Change
    • ALL
    • v4.0, v3.6, v3.4
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      Collection

      [
  {
    "array": [
      {
        "k": "field",
        "v": 1
      },
      {
        "k": "field",
        "v": 2
      }
    ]
  }
]

      Query

      db.collection.aggregate([
  {
    $project: {
      object: {
        $arrayToObject: "$array"
      }
    }
  },
  {
    $project: {
      "object": "$object",
      "field": "$object.field"
    }
  }
])

      Expected output

      [
  {
    "field": 1,
    "object": {
      "field": 1
    }
  }
]

      Actual output

      [
  {
    "field": 1,
    "object": {
      "field": 2
    }
  }
]
      Show
      Collection [ { "array" : [ { "k" : "field" , "v" : 1 }, { "k" : "field" , "v" : 2 } ] } ] Query db.collection.aggregate([ { $project: { object: { $arrayToObject: "$array" } } }, { $project: { "object" : "$object" , "field" : "$object.field" } } ]) Expected output [ { "field" : 1, "object" : { "field" : 1 } } ] Actual output [ { "field" : 1, "object" : { "field" : 2 } } ]
    • Query 2018-10-22

      Using $arrayToObject on an array of {k: ..., v: ...} objects where some k are repeating outputs an object that behaves inconsistently.

      Referencing this object as a whole using "$object" outputs an object with a field value that is different compared to the value obtained by referencing the field directly using "$object.field".

        1. 屏幕快照 2018-09-19 18.01.51.png
          123 kB
          Jakub Szypulka
        2. 屏幕快照 2018-09-19 18.18.32.png
          167 kB
          Jakub Szypulka

            Assignee:
            ian.boros@mongodb.com Ian Boros
            Reporter:
            jaksz Jakub Szypulka
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              Created:
              Updated:
              Resolved: