Append an object to an array inside a nested object

Question

I have a collection in MongoDB in which one of the documents looks like this:

{
  _id: ObjectId("6162883719592ea3350d3c87"),
  fullName: 'Random User',
  username: 'ruser1',
  password: 'asdadasd',
  portfolio: [ { equity: [] }, { crypto: [] }, { etf: [] }, { cash: [] } ]
}

I am trying to append a new object of the following format to the equity array inside the portfolio.

Object format:

{
  name : "AAPL",
  quantity : 1,
  price : 100
}

I was trying to use the $push to do this operation, but I'm encountering the following error:

db.users.updateOne( 
  {_id : ObjectId("6162883719592ea3350d3c87")},
  {$push : {"portfolio.equity" : {
    name : "AAPL",
    quantity : 1,
    price : 100
    }
  }
 }
)

MongoServerError: Cannot create field 'equity' in element {portfolio: [ { equity: [] }, { crypto: [] }, { etf: [] }, { cash: [] } ]}

I have also tried to use portfolio.$.equity, but that did not work either.

db.users.updateOne(
  {_id : ObjectId("6162883719592ea3350d3c87")} , 
  {$push : {"portfolio.$.equity" : {name : "AAPL", price : 100, quantity : 1}}}
)

MongoServerError: The positional operator did not find the match needed from the query.

In short, I am trying to append an object to an array inside an object's object.

How can I resolve this error or what is the appropriate way to do this?

Yong Shun · Accepted Answer · 2021-10-10 07:58:50Z

2

You can use arrayFilters with check portfolio.equity field is existed via $exists.

db.users.updateOne({
  _id: ObjectId("6162883719592ea3350d3c87")
},
{
  $push: {
    "portfolio.$[portfolio].equity": {
      name: "AAPL",
      price: 100,
      quantity: 1
    }
  }
},
{
  arrayFilters: [
    {
      "portfolio.equity": {
        $exists: true
      }
    }
  ]
})

Sample Mongo Playground

answered Oct 10, 2021 at 7:58

Yong Shun

54.6k6 gold badges38 silver badges66 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

mnikley Over a year ago

Didnt know mongoplayground exists, and that you can do such complex operations that easy. Thanks :)

thakreyn Over a year ago

@Yong Shun I appreciate your answer, but can you explain why do we have to use array filters? Why can't we directly push an object in the array?

Yong Shun Over a year ago

portfolio is an array. So portfolio.equity is invalid. arrayFilters is used to traverse the documents in the array with condition. For your case, as equity field is only existed in one document, so you need to filter the document which contains equity field. If you do $push with portfolio.$[].equity, all the documents in portfolio will be created new equity field.

Collectives™ on Stack Overflow

Append an object to an array inside a nested object

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related