Mongoose to count string array inside one document

Question

I'm trying to find a better performing solution maybe where you don't take the whole string array from collection and instead just return the count. Basically the countDocuments equivalent for a string array in one user collection.

I have a solution that works, but if that list gets really long then it won't be as good performance-wise.

                  User.findById(
                  { _id: req.params.id }, { _id: 0 })
                  .select("blacklistGroup").then((result) => {
                    let output = JSON.parse(JSON.stringify(result.blacklistGroup));
                    console.log(output.length + " + people");
                  });

I was hoping to get an example of a more efficient solution more aligned with countDocuments, but for string array. I appreciate the help!

Here is the model definition of blacklistGroup

  blacklistGroup: [String]

collection example

  "blacklistGroup": [
    "5e98e8e785e69146f841d239",
    "5e9867ff5e72550988820dd3",
    "5e98e90d85e69146f841d23a",
    "5e98c950f4fb3f63b4634e30",
    "5e99fcf3a506cf570056898b",
    "5e99fd15a506cf570056898c",
    "5e99fd3aa506cf570056898d",
    "5e99fd64a506cf570056898e",
    "5e99fda5a506cf570056898f"
  ]

Akash Kumar Verma · Accepted Answer · 2020-12-21 11:42:49Z

1

Try This One:

User.aggregate([
    {
        $match: { _id: req.params.id }
    }, 
    {
        $project: { blacklistGroupLength: { $size: '$blacklistGroup' } }
    }
])

edited Dec 21, 2020 at 11:42

Akash Kumar Verma

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answered Apr 17, 2020 at 19:33

Tina

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2 Comments

user6680 Over a year ago

I added this, but console.log(res) outputs []. It should say 10 pastebin.com/3w9BNVgE

user6680 Over a year ago

I got it working, but had to add mongoose.Types.ObjectId(req.params.id)

Ricardo · Accepted Answer · 2020-04-17 19:41:58Z

0

I've found something from MongoDB docs that might help you. Here is the link

answered Apr 17, 2020 at 19:41

Ricardo

1

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