How to only return the embedded objects from a document in mongodb

Question

I have the following model...

{
    username: 'bob',
    data: [
        {
            sport: 'football',
            events: [
                {
                    event: 1,
                    _id: 'h4jh234ht34j'
                },
                {
                    event: 2,
                    _id: '4h326ol2j3ld'
                },
                {
                    event: 2,
                    _id: 'fdsfasdfa3ws'
                }
                // ... more events
            ]
        },
        {
            sport: 'cricket',
            events: [
                {
                    event: 3,
                    _id: 'hd2g234ht3gj'
                },
                {
                    event: 2,
                    _id: '33326oldwqld'
                },
                {
                    event: 6,
                    _id: '461fa24gsa3s'
                }
                // ... more events
            ]
        },
        // ... more sports
    ]
}

Is there a way I can query this database to find any event objects where the event property equals 2? I want the query to return an array of objects for all the events from the different collections where the event = 2. Is this possible, or does the events array need to be an immediate ancestor of the "data" property?

Do you want the whole "bob" user document or just the events? — Rubén Vega
– Rubén Vega, Commented Aug 5, 2021 at 14:56

Rubén Vega · Accepted Answer · 2021-08-06 06:35:21Z

1

If you want to find the whole user document that contains some id you can do it just like this Playground 1

If you just want the matched events you could do it with $unwinds. Playground 2

Finally is you just want the event data, you could use $replaceRoot to get your expected result. Playground 3

edited Aug 6, 2021 at 6:35

answered Aug 5, 2021 at 15:07

Rubén Vega

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2 Comments

willmahon Over a year ago

Thank you, but although the model is what I want for the 2nd playground, the query returns the entire document when an object matches, but I only want it to return the object

Rubén Vega Over a year ago

@willmahon Edited with a 3rd playground just with the events info.

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