MongoDB nested Array find and projection

Question

I'm currently working with mongodb (mongoose). One of my example documents is:

myuser{
  _id: 7777...,
  money: 1000,
  ships:[{
    _id: 7777...
    name: "myshipname",
    products:[{
      product_id: 7777....,
      quantity: 24
    }]
  }
}

What I aim to do is to get a certain product given user id, ship id and product id, being the result something like: { product_id: 777..,quantity:24}

So far I got to find a certain user ship with:

findOne(userId,ships:{ $elemMatch: {_id:shipId}})

Which returns the information of the ship with shipId inside the array ships from user with userId. However, I cannot find the way to get only a certain product from that ship

angrykoala · Accepted Answer · 2015-11-12 22:42:18Z

1

What you want can probably best be done using the aggregation framework. Something like:

db.users.aggregate([
  {$match: { _id : <user>}},
  {$unwind: "$ships"},
  {$unwind: "$ships.products"},
  {$match: { "ships._id": <ship>}},
  {$match: { "ships.products.product_id": <product>}}
]);

Note I'm not on a computer with mongo right now, so my syntax might be a bit off.

edited Nov 12, 2015 at 22:42

angrykoala

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answered Nov 12, 2015 at 20:44

David says Reinstate Monica

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