MongoDB updating array object within an array

Question

Model structure:

{ _id: String, calc: [ { preset: String, datasets: [ { _id: String } ] } ] }

API route:

router.put('/:gameId/:preset/:datasetId', (req, res) => {
  Game.findOneAndUpdate({ _id: req.params.gameId, 'calc.preset': req.params.preset, 'calc.datasets._id': req.params.datasetId },
    { $set: { 'calc.$.datasets.$': req.body } })
    .then(() => res.status(200).json({ ...req.body, _id: req.params.datasetId }))
    .catch(err => res.status(500).json({ error: err }));
});

If I was to update an object inside calc array then I would: $set: { 'calc.$': newCalc }, so I followed the same approach in order to update an object that is inside datasets array, that is inside an object, that is inside calc array, however, $set: { 'calc.$.datasets.$': newDataset } doesn't work.

How to update an object with _id: req.params.datasetId, inside datasets array, that is inside calc array's object where the preset: req.params.preset?

In short: { calc: [ { datasets: [ { set this object to a new dataset } ] } }

Saravana · Accepted Answer · 2018-12-30 04:54:18Z

you can use $[] positional-all to updated nested array elements, mongo doc for $[]

query

db.t14.update(
   {},
   { $set: { "calc.$[].datasets.$[elem].name": "updated" } },
   { arrayFilters: [  { "elem": "x1" } ], multi: true}
)

sample collection with a document

> db.t14.findOne()
{
        "_id" : 1,
        "calc" : [
                {
                        "preset" : "abc",
                        "datasets" : [
                                {
                                        "_id" : "x1",
                                        "name" : "n1"
                                },
                                {
                                        "_id" : "x2",
                                        "name" : "n2"
                                }
                        ]
                }
        ]
}

update

> db.t14.update({},{$set: { "calc.$[].datasets.$[elem].name": "newname" } },{ arrayFilters: [{ "elem.name": "n1" }], multi: true})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

post update

> db.t14.findOne()
{
        "_id" : 1,
        "calc" : [
                {
                        "preset" : "abc",
                        "datasets" : [
                                {
                                        "_id" : "x1",
                                        "name" : "newname"
                                },
                                {
                                        "_id" : "x2",
                                        "name" : "n2"
                                }
                        ]
                }
        ]
}
>

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