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  1. Core Server
  2. SERVER-12573

Extend $ifNull to accept more than two arguments was Add $any/$first/$oneOf operator to projection

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    • Fully Compatible
    • Query 2020-11-30, Query 2020-12-14

      This could be described as $ifNull expression that accepts multiple arguments (rather than current two only). First non-null expression would be used.

      Original description:

      It would be great if instead of making a long list of conditionals you could use any $any operator to get the first of the fields that exists.

      Ex:

      var docs = [
  { 'a': true },
  { 'b': true },
  { 'a': true}
  ...
]

      { '$project':
  { 'wow':
    { '$any': [ '$a', '$b', '$b.nested', ... ] }
  }
}

      This would make it easy to project an _id for use by a $group stage in situations where you have varied document schema.

      For example, the next stage of the pipeline could be:

      { $group: 
  { 
    _id: { wow: '$wow' },
    count: { '$sum': 1 }
  }
}

            Assignee:
            hana.pearlman@mongodb.com Hana Pearlman
            Reporter:
            tyler@10gen.com Tyler Brock
            Votes:
            3 Vote for this issue
            Watchers:
            9 Start watching this issue

              Created:
              Updated:
              Resolved: