CODEWITHSUNDEEP
androidfirebasefirebase-realtime-database
MareCieco
MareCieco

Reputation: 157

Firebase Realtime Database Query Retrieve Records in Array - Android

I have a realtime database structure like below. Users have some friends. For example, I am Joe and I'd like to fetch users who have friends as Joe.

In this example, Dave and Harry have a friend called Joe, so my query should fetch Dave and Harry but shouldn't Micheal.

Is there a way to do this without fetching data in a loop?

{
"Users": {
    "Joe": {
        "Friends": ["Dave","Harry","Micheal"]
    },
    "Dave": {
        "Friends": ["Joe","Jack","Brent"]
    },
    "Harry": {
        "Friends": ["Jack","Joe"]
    },
    "Micheal": {
        "Friends": ["Ken","Jack","Brent"]
    }
}

}

Upvotes: 1

Views: 618

Answers (1)

Alex Mamo
Alex Mamo

Reputation: 138824

Firebase Realtime database cannot perform a query across array members, to see if it contains a specific value in any position or to add/remove a record. Firebase documentation recommends against using arrays. One of the many reasons Firebase recommends against using arrays is that it makes the security rules impossible to write.

As usual with NoSQL databases: if you can't perform the use-case you want with your current data structure, you can typically change/expand your data structure to allow the use-case. The best practice is to use maps instead of arrays. A possible database structure could look like this:

"Users": {
    "Joe": {
        "Friends"
            "Dave": true,
            "Harry": true,
            "Micheal": true
    },
    "Dave": {
        "Friends"
            "Joe": true,
            "Jack":true,
            "Brent": true

    },
    "Harry": {
        "Friends"
            "Jack": true,
            "Joe": true
    },
    "Micheal": {
        "Friends"
            "Ken":true,
            "Jack": true,
            "Brent": true
    }
}

You can also take a look, here, for more informations.

Upvotes: 1

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