MongoDB - Find in nested arrays

Question

My goal is to:

Get all the documents with status=true.
And return only objects with active=true in the life array.

Below is what my MongoDB documents look like:

{
    "name": "justine",
    "life" : [ 
        {
            "status" : true,
            "service" : [ 
                {
                    "partner" : "pat 1",
                    "active" : true,
                }, 
                {
                    "partner" : "pat 2",
                    "active" : false
                }
        }
    ]
},
{
    "name": "okumu",
    "life" : [ 
        {
            "status" : true,
            "service" : [ 
                {
                    "partner" : "pat 1",
                    "active" : true,
                }, 
                {
                    "partner" : "pat 2",
                    "active" : true
                }
        }
    ]
}

Expected output:

{
    "name": "justine",
    "life" : [ 
        {
            "status" : true,
            "service" : [ 
                {
                    "partner" : "pat 1",
                    "active" : true,
                }
        }
    ]
},
{
    "name": "okumu",
    "life" : [ 
        {
            "status" : true,
            "service" : [ 
                {
                    "partner" : "pat 1",
                    "active" : true,
                }, 
                {
                    "partner" : "pat 2",
                    "active" : true
                }
        }
    ]
}

This is what I did:

await Users.find({ life: { $elemMatch: { status: true, life: { $elemMatch: { active: false } } } }});

This is working well for the first condition, in case the second condition is not met, the entire object is not returned, however, if it's met, even the active=false objects are returned.

I'll be grateful if you can help me out, am not a MongoDB expert.

Yong Shun · Accepted Answer · 2022-04-25 02:28:57Z

1

I think it is complex (possible not doable) with the .find() query.

You should use .aggregate() query.

$match - Filter document with life.status is true.
$project -

2.1 $filter - Filter the document with status is true in life array document.

2.1.1 $map - Merge the life document with the Result 2.1.1.1.

2.1.1.1 $filter - The inner $filter operator to filter the document with active is true for service document in service array.

db.collection.aggregate([
  {
    $match: {
      "life.status": true
    }
  },
  {
    $project: {
      name: 1,
      life: {
        "$filter": {
          "input": {
            "$map": {
              "input": "$life",
              "in": {
                "$mergeObjects": [
                  "$$this",
                  {
                    "service": {
                      "$filter": {
                        "input": "$$this.service",
                        "as": "service",
                        "cond": {
                          $eq: [
                            "$$service.active",
                            true
                          ]
                        }
                      }
                    }
                  }
                ]
              }
            }
          },
          as: "life",
          "cond": {
            $eq: [
              "$$life.status",
              true
            ]
          }
        }
      }
    }
  }
])

Sample Mongo Playground

edited Apr 25, 2022 at 2:28

answered Apr 25, 2022 at 2:23

Yong Shun

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3 Comments

YuTing Over a year ago

I still wonder why your profile photo looks like an error file. Maybe it's bug from SO ?

Yong Shun Over a year ago

Haha, my profile was linked with Facebook. And due to the Facebook account no longer being accessible, it shows a broken file.

YuTing Over a year ago

Oh okay, now I get it ! Maybe SO should stored the photo in it's own database instead of stored only the link. I like your answer and I up vote it.

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