Question 239726 in Mongodb Question posted in
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Best way to push object to mongodb array, without duplicating data

In mongodb, is it possible to use $addToSet to test a certain object field for duplications, rather than the object as a whole?

For instance, when storing cookies found on a webpage, ie:

db.audits.insertOne( { _id: 1, cookies: [{name: "xx", value: "abc", ...}]})

can $push or $addToSet be used in a way whereby new objects are considered duplicates if they match the name field already present in the array? ie:

db.audits.updateOne(
   { _id: 1 },
   { $addToSet: { cookies: { $each: [ {name: "xx", value: "def"}, {name: "yy", value: "abc"} ] } } }
 )

desired result is for only {name: "yy",..} to be added to the array.

Tags:

2

Answers


  1. 0

    One option is to use update with pipeline with $filter:

    db.audits.updateOne(
  { _id: 1 },
  [{
    $set: {cookies: {$concatArrays: [
          "$cookies",
          {$filter: {
              input: [
                {name: "xx", value: "def"},
                {name: "yy", value: "abc"}
              ],
              cond: {$not: {$in: ["$$this.name", "$cookies.name"]}}
          }}
    ]}}
  }]
)

    See how it works on the playground example

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  2. 0

    Here is the working example with update aggregate :

    Data:

    [
  {
    _id: 1,
    cookies: [
      {
        name: "abc",
        value: "123"
      }
    ]
  },
  {
    _id: 2,
    cookies: [
      {
        name: "abc",
        value: "456"
      },
      {
        name: "some",
        value: "789"
      }
    ]
  },
  {
    _id: 3,
    cookies: []
  }
]

    Aggregate:

    db.collection.update({},
[
  {
    $addFields: {
      "cookies": {
        $setUnion: [
          "$cookies",
          {
            $filter: {
              input: [
                {
                  name: "abc",
                  value: "def"
                },
                {
                  name: "yy",
                  value: "abc"
                }
              ],
              cond: {
                $not: {
                  $in: [
                    "$$this.name",
                    "$cookies.name"
                  ]
                }
              }
            }
          }
        ]
      }
    }
  }
],
{
  multi: true
})

    Output:

    [
  {
    "_id": 1,
    "cookies": [
      {
        "name": "abc",
        "value": "123"
      },
      {
        "name": "yy",
        "value": "abc"
      }
    ]
  },
  {
    "_id": 2,
    "cookies": [
      {
        "name": "abc",
        "value": "456"
      },
      {
        "name": "some",
        "value": "789"
      },
      {
        "name": "yy",
        "value": "abc"
      }
    ]
  },
  {
    "_id": 3,
    "cookies": [
      {
        "name": "abc",
        "value": "def"
      },
      {
        "name": "yy",
        "value": "abc"
      }
    ]
  }
]
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