Question 161866 in Mongodb Question posted in
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What is the aggregation version of $not in MongoDB?

{ field_name: { $not: { $lt: 100 } } }

How do I write the above using MongoDB aggregation language?

I cannot use:

{ $gte: ["$field_name", 100] }

because field_name may be missing. When it is missing, then it should always be true. This is the reason why I use $not.

The should be able to use indexes on field_name

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2

Answers


  1. 0

    $not with $gt (not greater than) is equivalent to $lte (lesser or equal to).

    While you can use the $ifNull operator to define the default value if the field is null or missing.

    db.collection.aggregate([
  {
    $match: {
      $expr: {
        $lte: [
          {
            $ifNull: [
              "$field_name",
              0
            ]
          },
          100
        ]
      }
    }
  }
])

    Demo @ Mongo Playground

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  2. 0

    What is your problem? It should just work:

    db.collection.insertMany([
   { field_name: 50 },
   { field_name: 150 },
   { other_field: 0 },
   { field_name: null }
])

db.collection.find({ field_name: { $not: { $lt: 100 } } })    
[
  { _id: ObjectId("6459fc29927c6f7dd310d586"), field_name: 150 },
  { _id: ObjectId("6459fc29927c6f7dd310d587"), other_field: 0 },
  { _id: ObjectId("6459fc8e927c6f7dd310d588"), field_name: null }
]


db.collection.aggregate([{ $match: { field_name: { $not: { $lt: 100 } } } }])
[
  { _id: ObjectId("6459fc29927c6f7dd310d586"), field_name: 150 },
  { _id: ObjectId("6459fc29927c6f7dd310d587"), other_field: 0 },
  { _id: ObjectId("6459fc8e927c6f7dd310d588"), field_name: null }
]

    Index is used in either cases.

    $match documentation:

    The $match stage has the following prototype form:

    { $match: { <query> } }

    $match takes a document that specifies the query conditions. The query syntax is identical to the read operation query syntax

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