MongoDB - Update array with $addToSet and set array's length with { '$size': '$array' } not working

Question

I am working on MongoDB, which has a model as below:

const appJobSchema = new mongoose.Schema({
    data: [
      { type: Schema.Types.Mixed }
    ],
    stat: {
      dataCount: { type: Number, default: 0 },
    }
})

What I need to do is to update a few records in the array field, at the same time update the latest array length to the stat.dataCount field.

export async function updateDataById(id: string, records: any[]) {
  return await model.updateOne({ '_id': id }, {  
    '$addToSet': { 'data': { '$each': records } } ,  
    '$set': { 
      'stat.dataCount': { $size: "$data" }  
    } 
  });
}

But I got an error saying:

UncaughtException: Cast to Number failed for value "{ '$size': '$data' }" (type Object) at path "stat.dataCount"

Any idea how I would do it?

Update

First try on the pipeline:

return await model.updateOne({'_id':id}, 
  [
    {
      "$set": {
        "data": {
          $concatArrays: [ "$data",  records ]
        }
      }
    },
    { 
      '$set': { 
        'stat.dataCount': { $size: "$data" } }  
    }
  ]);

It is working, but the problem is that solely adding values to the data array would cause duplicate values, and that is why I have to use $addToSet in order to remove the duplicates.

Second try on the pipeline:

Model.updateOne({'_id':id},
  [
      { '$addToSet': { 'data': { '$each': records } }, '$inc':{ 'runCount': 1  } , 
      { 
        '$set': { 
          'stat.dataCount': { $size: "$data" } }  
      }
  ]);

It throws out:

UncaughtException: Invalid update pipeline operator: "$addToSet".

Same for $inc.

Finally get it working by $setUnion with pipeline,

await Model.updateOne({'_id':id},
  [   
    {
      "$set": {
        "data": {
          $setUnion: [ "$data",  records  ]
        }
      }
    },
    { 
      '$set': { 
        'stat.dataCount': { $size: "$data" }  }  
    },
  ]);

But what if I need to use $inc? It still seems a problem.

MongoDB $inc is the update operator, since you change it to pipeline, you should revamp to $set and $sum to increment the value: { $set: { 'runCount': { $sum: [ '$runCount', 1] } } } — Yong Shun
– Yong Shun, Commented Feb 4 at 1:09

Yong Shun · Accepted Answer · 2025-02-04 04:09:52Z

2

As you are switching to the update pipeline to use the aggregation operator, the update operator is not supported. You need to switch to all aggregation operators, such as $sum to replace the $inc.

await Model.updateOne({'_id':id},
  [   
    {
      "$set": {
        "data": {
          $setUnion: [ "$data",  records  ]
        },
        "runCount": { 
          $sum: [ "$runCount", 1 ]  
        }
      }
    }
  },
  { 
    "$set": { 
      "stat.dataCount": { $size: "$data" }  
    }
  },
]);

edited Feb 4 at 4:09

answered Feb 4 at 1:15

Yong Shun

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