Question 290429 in Mongodb Question posted in
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mongodb find by array specified index and create index for this usage

There is a document

{i:[1,2,3,4,5,6]}

and need to find by array element value with specified index:

find({ $and: [ {"i.0": 1}, {"i.1": 2} ] })

However, this can not take vantadge of index of createIndex({i:1})
This kind index seems only work for elemMatch like:

find({ i: { $elemMatch: { $gte: 80, $lt: 85 } } })

Does there have anyways to create index which useful in finding specified index of array like "i.n"?

Tags:

2

Answers


  1. 0

    What about this:

    db.collection.aggregate([
   {
      $match: {
         $expr: {
            $and: [
               { $eq: [{ $arrayElemAt: ["$i", 0] }, 1] },
               { $eq: [{ $arrayElemAt: ["$i", 1] }, 2] }
            ]
         }
      }
   }
])

    Mongo Playground

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  2. 0

    You can create an index on the fields like you query them.

    For example, the index

    createIndex({"i.0":1, "i.1":1})

    would do a good job of servicing the query

    find({ $and: [ {"i.0": 1}, {"i.1": 2} ] })
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