mongoose search using regex on findbyid

Question

I need to find a user by his mongodb collection's _id ,

in need the search to be done using the first 5 characters in the user id

example with 5e9cca i can find the collection id 5e9cca24beabb96a4caedc35

    var id = req.body.id

    User.findById({ _id : { $regex: '^id', $options: 'i' } },  
     (err, user)  => {
        if (err) {
             console.log(err);
           res.status(400)
       }

with this code i got this error :

MongooseError [CastError]: Cast to ObjectId failed for value "{ _id: { '$regex': '^id', '$options': 'i' } }" at path "_id" for model "User"

PS : The search using the hole id is working

whoami - fakeFaceTrueSoul · Accepted Answer · 2020-04-22 16:47:20Z

4

Mongoose's .findById() will take in a string & internally it will convert string into ObjectId(). So .findById() is kind of a wrapper to MongoDB's native function .findOne() and all it can take is a string. Additionally you can not do regex search on _id field as it's not of type string. If at all you need to do this, try below :

On MongoDB version >4.0 :

db.collection.aggregate([
  /** Create a field of type 'string' from `_id`*/
  { $addFields: { convertedId: { $toString: "$_id" } } },
  /** Regex search against it */
  {
    $match: {
      convertedId: {
        $regex: "^1a934e",
        $options: "i"
      }
    }
  },
  /** Remove additionally added field */
  { $project: { convertedId: 0 } }
])

Test : mongoplayground

answered Apr 22, 2020 at 16:47

whoami - fakeFaceTrueSoul

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