Multiple Geofire queries and client-side filtering

Question

I've been referring to this SO post for a few days now: Filtering results with Geofire + Firebase

My issue is that for my iOS app I need to make a single list of nearby users that is ordered by credentials, for example: premium member (highest and at top of list), donator (next highest after premium), member (basic/lowest).

I've created 3 entries in my Firebase server for GeoFire locations that split users based on these credentials, and therefore need to run 3 queries to retrieve them.

GeoFire* geoFirePremium = [[GeoFire alloc] initWithFirebaseRef:[[[FIRDatabase database] reference] child:@"geofire-premium-members"]];
GeoFire* geoFireDonator = [[GeoFire alloc] initWithFirebaseRef:[[[FIRDatabase database] reference] child:@"geofire-donator-members"]];
GeoFire* geoFireRegular = [[GeoFire alloc] initWithFirebaseRef:[[[FIRDatabase database] reference] child:@"geofire-regular-members"]];
NSMutableDictionary* query1Items = [[NSMutableDictionary alloc] init];
NSMutableDictionary* query2Items = [[NSMutableDictionary alloc] init];
NSMutableDictionary* query3Items = [[NSMutableDictionary alloc] init];

CLLocation* coord = [[CLLocation alloc] initWithLatitude:34.2499 longitude:-85.4399]; // Test location
long searchDistance = 8;
float mile2Kilo = 1.60934;
float kilo2mile = 0.62137;
GFCircleQuery* query1 = [geoFirePremium queryAtLocation:coord withRadius:(CGFloat)(searchDistance * mile2Kilo)]; // Miles to Kilometers
[query1 observeEventType:GFEventTypeKeyEntered withBlock:^(NSString* key, CLLocation* location)
{
    // Store results in query1Items
}];
GFCircleQuery* query2 = [geoFireDonator queryAtLocation:coord withRadius:(CGFloat)(searchDistance * mile2Kilo)];
[query2 observeEventType:GFEventTypeKeyEntered withBlock:^(NSString* key, CLLocation* location)
{
    // Store results in query2Items
}];
GFCircleQuery* query3 = [geoFireRegular queryAtLocation:coord withRadius:(CGFloat)(searchDistance * mile2Kilo)];
[query3 observeEventType:GFEventTypeKeyEntered withBlock:^(NSString* key, CLLocation* location)
{
    // Store results in query3Items
}];

My thoughts are to add some code that recognizes when all 3 queries complete and then merges them into 1 list.

NSMutableDictionary* mergedItems = [[NSMutableDictionary alloc] init];
// For example:  { query1Items[], query2Items[], query3Items[], ... }

[query1 observeReadyWithBlock:^{
    NSLog(@"Query 1 is finished");
    // Check for queries 2 & 3 completion
    // Perform merge if all are completed
}];
[query2 observeReadyWithBlock:^{
    NSLog(@"Query 2 is finished");
    // Check for queries 1 & 3 completion
    // Perform merge if all are completed
}];
[query3 observeReadyWithBlock:^{
    NSLog(@"Query 3 is finished");
    // Check for queries 1 & 2 completion
    // Perform merge if all are completed
}];

Where the JSON structure for all Firebase/GeoFire references follows:

- geofire-premium-members
    - userid
        - g: geohash
        - l
            - 0: lat
            - 1: lon

- geofire-donator-members   //same format

- geofire-regular-members   //same format

- users
    - userid
        - …

Is it a good approach to use multiple queries like this? It is possible I may need to add more credentials in the future and do not know if my approach will scale well. Is there perhaps a better way to achieve what I need that maybe only uses a single query instead? I greatly appreciate any insight

Answer 1

There's nothing wrong with your concept. It may be over complex though as there are three queries to return the same type of data and combining the data in code and doing additional queries to get other user data.

i.e. The three queries in the code return a bunch of user id's to which you then need to do more queries to (for example) look up the individual users names

As long as all of the members in the users node have the same structure you could just put them in one node and use a child property to indicate what kind of user they are

userid_0
    name: "some name"
    user_type: "regular"
userid_1
    name: "another name"
    user_type: "donator"

Then the GeoFire query to return all users within the specified radius.

Assuming the users have to be looked up for their name (as an example) anyway, you will have the rest of the data in the user node and can simply read them in, sort by user_type (in code) and display.

That being said, if you know for sure how you want them sorted, then a simple change to the structure will allow for that easily.

userid_0
    name: "some premium name"
    user_type: 0
userid_1
    name: "a donator name"
    user_type: 1
user_id_2
    name: "regular name"
    user_type: 2

where 0 = a premium user, 1 = a donator user and 2 is a regular user.

Then when sorting in code, sort by user_type and the premiums will float to the top.