Cloud Firestore query result set is empty

Question

I am trying to run the below query on the sample data provided in firebase docs here:

cities.whereLessThan("population", 9000000)
        .whereGreaterThan("population", 9000000)
        .get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        if(task.isSuccessful()) {
            Logger.log_error(TAG + " Task successful Result is Empty = " + task.getResult().isEmpty());
        }else {
            Logger.log_error(TAG + " Task failed = " + task.getException().getMessage());
        }
    }
});

I am expecting to get cities where the population is less than 9000000 and greater than 9000000. Eventually what I am trying to achieve is: select * from TABLE where population <> 9000000 by combining whereLessThan and whereGreaterThan in the FireStore query.

Can someone please let me know if it isn't supported at all or am I wrong somewhere?

score 1 · Accepted Answer · answered Nov 25 '17 at 16:31

1

Firestore query conditions are ANDed together. So what you're asking for is: give me a cities with more than 9 million and with less than 9 million people. That's an empty set: no city can have both more and less than 9 million.

answered Nov 25 '17 at 16:31

Frank van Puffelen

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So stupid of me! I have gone thru the documentation 10 times but still missed the same. Thanks for the explanation :) – Rahul Shukla Nov 27 '17 at 03:30
But is there a way to achieve what I intend to? – Rahul Shukla Nov 27 '17 at 03:31
There is no built-in support for "not equal" operations. See https://stackoverflow.com/questions/47251919/firestore-how-to-perform-a-query-with-inequality-not-equals – Frank van Puffelen Nov 27 '17 at 15:15

score 0 · Answer 2 · answered Nov 25 '17 at 15:09

If you haven't already I believe you have to create a Cloud Firestore index

in short:

Cloud Firestore requires an index for every query, to ensure the best performance. All document fields are automatically indexed, so queries that only use equality clauses don't need additional indexes. If you attempt a compound query with a range clause that doesn't map to an existing index, you receive an error. The error message includes a direct link to create the missing index in the Firebase console.

Cloud Firestore query result set is empty

2 Answers2