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  1. Core Server
  2. SERVER-58521

Dot notation updates with arrays can lead to nonsensical results

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Duplicate
    • None
    • None
    • None
    • None
    • Query Optimization
    • ALL
    • Hide 

      Enterprise test> db.dropDatabase()
      		 
      Enterprise test> db.test.insert({_id: 1, arr_a: [1, 3]});
      		 
      Enterprise test> db.test.insert({_id: 2, arr_a: [1, 3]});
      		 
      Enterprise test> db.test.updateOne({_id: 1}, {$set: {"arr_a.0": 2}});    
      Enterprise test> db.test.updateOne({_id: 2}, [{$set: {"arr_a.0": 2}}]);
      		 
      Enterprise test> db.test.find()
      		 
      [
      		 
        { _id: 1, arr_a: [ 2, 3 ] },
      		 
        { _id: 2, arr_a: [ { '0': 2 }, { '0': 2 } ] }
      		 
      ]

      Show
      Enterprise test> db.dropDatabase() Enterprise test> db.test.insert({_id: 1, arr_a: [1, 3]}); Enterprise test> db.test.insert({_id: 2, arr_a: [1, 3]}); Enterprise test> db.test.updateOne({_id: 1}, {$set: {"arr_a.0": 2}}); Enterprise test> db.test.updateOne({_id: 2}, [{$set: {"arr_a.0": 2}}]); Enterprise test> db.test.find() [ { _id: 1, arr_a: [ 2, 3 ] }, { _id: 2, arr_a: [ { '0': 2 }, { '0': 2 } ] } ]

    Description

      The documentation isn't clear that dot notation behaviour with arrays using $set provides very different results than using $set with arrays.

      The behaviour is surprising.

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        Issue Links

          duplicates

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-24748 Aggregation does not provide a way to access a specific element of an array

          • Major - P3 - Major loss of function.
          • Backlog
          related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-27442 Positional path component in match language should not act as both an array index and a field name for a single document

          • Major - P3 - Major loss of function.
          • Backlog

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-24748 Aggregation does not provide a way to access a specific element of an array

          • Major - P3 - Major loss of function.
          • Backlog

          Activity

            People

              backlog-query-optimization Backlog - Query Optimization
              ross@mongodb.com Ross Lawley
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              Dates

                Created:
                Updated:
                Resolved: