Firestore use contains on multiple fields

Question

I have an upcoming video games app. A game release can come out on multiple platforms. I heard that firestore is much more flexible than firebase real time database on how you can retrieve your data. I'm stuck on how can I check if my game release documents in my release collection contains the user chosen platforms, so the app can show the games coming out on his platforms.

This is what I currently have

platforms is a list of Integer which contains platforms ids

  databaseReference.collection(getRegionNode())
            .whereEqualTo("m_y", monthFilter)
            .whereArrayContains("platforms", platforms)
            .orderBy("date", Query.Direction.ASCENDING).get().addOnCompleteListener(listener);

Here's an example of a game release document:

   1369: { 
        "src": "Images/dead.png",
        "name": "red dead 2",
        "date": 2018-10-26,
        "region": worldwide,
        "platforms": "[12, 13, 54]"
    }

Let's say for example, user wants to only be shown platform 12 and 13 games, I want a query that checks and retrieves all releases documents where 12 and 13 are in their platforms list. Thank you!

What is the value of the second argument passed in `.whereArrayContains("platforms", platforms)`? — Alex Mamo, Nov 01 '18 at 06:12
Can you please give me a concrete example on what you exactly pass? — Alex Mamo, Nov 01 '18 at 06:16
So the value of the seond argument that you pass is an array? — Alex Mamo, Nov 01 '18 at 06:17

Alex Mamo · Accepted Answer · 2018-11-01T08:27:27.173

Firestore Query's whereArrayContains(String field, Object value):

Creates and returns a new Query with the additional filter that documents must contain the specified field, the value must be an array, and that the array must contain the provided value.

According to your comments, your platforms object that is passed as the second argument to this method is of type array. What you are actually doing, you are searching in the platforms property which is of type array for an array, which is not possible since the platforms array in your database contains numbers:

"platforms": "[12, 13, 54]"

And not arrays. A query like this:

databaseReference.collection(getRegionNode())
        .whereEqualTo("m_y", monthFilter)
        .whereArrayContains("platforms", 12) //Passed a number as the second argument
        .orderBy("date", Query.Direction.ASCENDING).get().addOnCompleteListener(listener);

Will work fine because we are searching within the platforms array for a number. Please also note, if you intend to use this king of query, an index is required. For how to create an index, please see my answer from this post.

Even if you using the above query, you can filter your items using only one whereArrayContains() method call. If you will use more than one, the following error will occur:

Caused by: java.lang.IllegalArgumentException: Invalid Query. Queries only support having a single array-contains filter.

If you need to filter on more than one platform, you'll need to change the logic of structuring your database by creating a property for each individual platform that you have and chain whereEqualTo() method calls. I know it sounds a little weird but this is how Cloud Firestore works.

Your schema should like this:

1369: { 
    "src": "Images/dead.png",
    "name": "red dead 2",
    "date": 2018-10-26,
    "region": worldwide,
    "platformsOne": 12,
    "platformsTwo": 13,
    "platformsThree": 54
}

To find all the games for platform 12, 13 and 54, you should use a query that looks like this:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
Query query = rootRef.
    .whereEqualTo("platformsOne", 12)
    .whereEqualTo("platformsTwo", 13)
    .whereEqualTo("platformsThree", 54);

I can also do it like so https://stackoverflow.com/questions/46687714/how-to-query-documents-which-contains-a-sent-parameter-in-firestore no? Which do you think is better? — , Nov 02 '18 at 00:21
Yes you can. Both are considered better but you can do it the way you are confortable with. — Alex Mamo, Nov 02 '18 at 06:14

Firestore use contains on multiple fields

1 Answers1