Data from GET is returned differently then how the data is stored for map values

Question

For example, here's how my data is stored:

When I do a GET for the data from this URL (using the REST API):

https://<redacted>.com/maps/a6c00d68a95a5043374c1017b982d8f0b3009179/data/003_teleportIns.json

The result looks like this:

[{"sequenceNumber":0,"x":8,"y":3},{"sequenceNumber":1,"x":3,"y":14},{"sequenceNumber":2,"x":11,"y":15}]

What I expected, was for the data to look like this instead:

{"0":{"sequenceNumber":0,"x":8,"y":3},"1":{"sequenceNumber":1,"x":3,"y":14},"2":{"sequenceNumber":2,"x":11,"y":15}}

Since I'm using kotlinx serialization to decode the data, the way that firebase returns the data results in errors when trying to decode.

Here's an example error:

Unexpected JSON token at offset 199: Expected start of the object '{', but had ':' instead
JSON input: .....":5,"y":7}],
"003_teleportIns":[{"sequenceNumber":0,"x":8,"y.....
kotlinx.serialization.json.internal.JsonDecodingException: Unexpected JSON token at offset 199: Expected start of the object '{', but had ':' instead
JSON input: .....":5,"y":7}],
"003_teleportIns":[{"sequenceNumber":0,"x":8,"y.....

So what gives? Why is firebase returning my data in an unexpected manor? If this is expected, please point me to the documentation.

Answer 1

If you have sequential numeric keys in the result, the Firebase REST API (and SDKs) returns those as an array. There is no way to change this behavior, so what I usually do is prefix those keys with a short non-numeric string to prevent the array coercion. So "key_0", "key_1", etc.

Also see Best Practices: Arrays in Firebase.