Crash when running collectionGroup query in Cloud Firestore (Swift) - ios

Question

I run a mobile app project using Swift, SwiftUI and Cloud Firestore where I need to find users based on their different settings/preferences. I have solved this by using a collectionGroup query. But sometimes (maybe 1 out of 10 times) the query crashes without any (for me) understandable error message. The composite indexes have been created using the http links provided from XCode.
This is the function I use:
func getUsersFromActivityPrefs(genders:[String], activities:[Int],skillScore_min:Int, skillScore_max:Int,completion:#escaping ([String]) -> ()) {
var matchUsers = [String]()
var count = 0
let db = Firestore.firestore()
for gender in genders {
for activity in activities {
let dbRef = db.collectionGroup("activity_preferences")
.whereField("gender", isEqualTo: gender)
.whereField("activityid", isEqualTo: activity)
.whereField("status", isEqualTo: true)
.whereField("skill_score", isGreaterThanOrEqualTo: skillScore_min)
.whereField("skill_score", isLessThanOrEqualTo: skillScore_max)
.limit(to: 100)
dbRef.getDocuments {( snap, err) in
count+=1
if err != nil {
print(err!.localizedDescription)
}
for i in snap!.documentChanges{
let uid = i.document.get("uid") as? String ?? ""
if uid != "" && !matchUsers.contains(uid) {
matchUsers.append(uid)
if matchUsers.count == 100 {
count = genders.count * activities.count
completion(matchUsers) //escaping completion handler
return
}
}
}
if count == genders.count * activities.count {
completion(matchUsers)
return
}
}
}
}
}
I have attached the trace log and the crash message from XCode. Im using the latest version of Firebase SDK and deployment target is iOS14.
This is the trace log I get:
thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x4f)
frame #0: 0x00007fff4b80dd66 AttributeGraphAG::Graph::input_value_ref_slow(AG::data::ptr<AG::Node>, AG::AttributeID, unsigned int, AGSwiftMetadata const*, bool*, long) + 322 frame #1: 0x00007fff4b81f1a5 AttributeGraphAGGraphGetValue + 203
frame #2: 0x00007fff55e7ffab SwiftUISwiftUI.DynamicBody.phase.getter : SwiftUI._GraphInputs.Phase + 27 frame #3: 0x00007fff55e80176 SwiftUISwiftUI.DynamicBody.updateValue() -> () + 294
frame #4: 0x00007fff55b9583a SwiftUIpartial apply forwarder for implicit closure #2 (Swift.UnsafeMutableRawPointer, __C.AGAttribute) -> () in implicit closure #1 (A1.Type) -> (Swift.UnsafeMutableRawPointer, __C.AGAttribute) -> () in closure #1 () -> (Swift.UnsafeMutableRawPointer, __C.AGAttribute) -> () in closure #1 (Swift.UnsafePointer<A1>) -> AttributeGraph.Attribute<A> in AttributeGraph.Attribute.init<A where A == A1.Value, A1: AttributeGraph.StatefulRule>(A1) -> AttributeGraph.Attribute<A> + 26 frame #5: 0x00007fff4b808d03 AttributeGraphAG::Graph::UpdateStack::update() + 505
frame #6: 0x00007fff4b809199 AttributeGraphAG::Graph::update_attribute(AG::data::ptr<AG::Node>, bool) + 335 frame #7: 0x00007fff4b80d8e8 AttributeGraphAG::Graph::value_ref(AG::AttributeID, AGSwiftMetadata const*, bool*) + 130
frame #8: 0x00007fff4b81f1f3 AttributeGraphAGGraphGetValue + 281 frame #9: 0x00007fff561aeeb7 SwiftUISwiftUI.GraphHost.updatePreferences() -> Swift.Bool + 39
frame #10: 0x00007fff55c9a8cf SwiftUISwiftUI.ViewGraph.updateOutputs(at: SwiftUI.Time) -> () + 95 frame #11: 0x00007fff5611310c SwiftUIclosure #1 () -> () in (extension in SwiftUI):SwiftUI.ViewRendererHost.render(interval: Swift.Double, updateDisplayList: Swift.Bool) -> () + 1308
frame #12: 0x00007fff56112327 SwiftUI(extension in SwiftUI):SwiftUI.ViewRendererHost.render(interval: Swift.Double, updateDisplayList: Swift.Bool) -> () + 343 frame #13: 0x00007fff55ba07de SwiftUIclosure #1 () -> () in SwiftUI._UIHostingView.requestImmediateUpdate() -> () + 62
frame #14: 0x00007fff562739ae SwiftUIreabstraction thunk helper from #escaping #callee_guaranteed () -> () to #escaping #callee_unowned #convention(block) () -> () + 14 frame #15: 0x0000000112ebd8ac libdispatch.dylib_dispatch_call_block_and_release + 12
frame #16: 0x0000000112ebea88 libdispatch.dylib_dispatch_client_callout + 8 frame #17: 0x0000000112eccf23 libdispatch.dylib_dispatch_main_queue_callback_4CF + 1152
frame #18: 0x00007fff203a8276 CoreFoundation__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9 frame #19: 0x00007fff203a2b06 CoreFoundation__CFRunLoopRun + 2685
frame #20: 0x00007fff203a1b9e CoreFoundationCFRunLoopRunSpecific + 567 frame #21: 0x00007fff2b773db3 GraphicsServicesGSEventRunModal + 139
frame #22: 0x00007fff24660af3 UIKitCore-[UIApplication _run] + 912 frame #23: 0x00007fff24665a04 UIKitCoreUIApplicationMain + 101
frame #24: 0x000000010db84a5b Sparringmain at AppDelegate.swift:14:7 frame #25: 0x00007fff20257415 libdyld.dylibstart + 1
Attachments:
Crash in XCode 1
Composite index 2

Answer 1

func getUsersFromActivityPrefs(genders: [String], activities: [Int], skillScore_min: Int, skillScore_max: Int, completion: #escaping ([String]) -> Void) {
var matchUsers = [String]()
var count = 0
let db = Firestore.firestore()
let dispatch = DispatchGroup() // instantiate dispatch group outside loop
for gender in genders {
for activity in activities {
dispatch.enter() // enter group on each iteration
let dbRef = db.collectionGroup("activity_preferences")
.whereField("gender", isEqualTo: gender)
.whereField("activityid", isEqualTo: activity)
.whereField("status", isEqualTo: true)
.whereField("skill_score", isGreaterThanOrEqualTo: skillScore_min)
.whereField("skill_score", isLessThanOrEqualTo: skillScore_max)
.limit(to: 100)
dbRef.getDocuments {( snap, err) in
if let snap = snap {
count += 1
for doc in snap.documents {
if let uid = doc.get("uid") as? String,
!matchUsers.contains(uid) {
matchUsers.append(uid)
}
}
} else if let err = err {
print(err)
}
dispatch.leave() // always leave no matter what the db returned
}
}
}
/*
this is the group's completion handler and it's only
called once after all groups have entered and left
*/
dispatch.notify(queue: .main) {
completion(matchUsers)
}
}