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Cache snapshot listener prevents getDocuments() from fetching most recent data

Open mattwiechec opened this issue 1 week ago • 1 comments

Description

Adding a snapshot listener with SnapshotListenOptions().withSource(.cache) to a collection causes subsequent gets to return old data.

Extra notes:

  • Not adding the listener causes normal behaviour. All calls to getDocuments() return most recent data.
  • From the debug log, I can see that the second call to getDocuments() does not print 12.6.0 - [FirebaseFirestore][I-FST000001] Using full collection scan to execute query: Query(canonical_id=users|f:|ob:__name__asc) when the cache listener is in place.
  • A workaround I found is to use a more complex query, ie: Firestore.firestore().collection("users").order(by: "name"). Adding order to the query fixes the issue.

Reproducing the issue

  1. Initialize a basic Firebase project with Firestore configured. Nothing fancy here, just a bare bones setup.
  2. Run the Emulator. (I am running with: firebase emulators:start --project demo-123)
  3. Using the Emulator UI, add a users collection, and a user document with a name field. Image
  4. Run the iOS app (sample code below)
import UIKit
import FirebaseFirestore

class ViewController: UIViewController {

    private var cacheListenerRegistration: ListenerRegistration?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        subscribeToCache()
    }

    private func subscribeToCache() {
        let options = SnapshotListenOptions().withSource(.cache)
        
        cacheListenerRegistration = Firestore.firestore().collection("users").addSnapshotListener(options: options) { querySnapshot, error in
        }
    }

    @IBAction func onFetchFromServer() {
        print("onFetchFromServer")
        Firestore.firestore().collection("users").getDocuments(source: .server) { (querySnapshot, error) in
            if let error {
                print("Error getting documents: \(error)")
            } else {
                for document in querySnapshot!.documents {
                    print("\(document.documentID) hasPendingWrites=\(document.metadata.hasPendingWrites) isFromCache=\(document.metadata.isFromCache) \(document.data())")
                }
            }
        }
    }
}
  1. Invoke onFetchFromServer(). The first time this is called it will fetch the correct data from the server. 
    nBWNES6LPP6NlDC5i7Vd hasPendingWrites=false isFromCache=false ["name": Matt]
  2. Using the Emulator UI, update the name field in the document. Image
  3. Invoke onFetchFromServer() again. This will fetch outdated data but show isFromCache = false. 
    nBWNES6LPP6NlDC5i7Vd hasPendingWrites=false isFromCache=false ["name": Matt]

Firebase SDK Version

12.6

Xcode Version

16.4

Installation Method

Swift Package Manager

Firebase Product(s)

Firestore

Targeted Platforms

iOS

Relevant Log Output

12.6.0 - [FirebaseCore][I-COR000001] Configuring the default app.
12.6.0 - [FirebaseFirestore][I-FST000001] Initializing. Current user:
12.6.0 - [FirebaseFirestore][I-FST000001] Using full collection scan to execute query: Query(canonical_id=users|f:|ob:__name__asc)
12.6.0 - [FirebaseFirestore][I-FST000001] RemoteStore 313039353137623530 restarting streams as connectivity changed
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) stop
12.6.0 - [FirebaseFirestore][I-FST000001] WriteStream (313039313165623038) stop
12.6.0 - [FirebaseCore][I-COR000033] Data Collection flag is not set.
void * _Nullable NSMapGet(NSMapTable * _Nonnull, const void * _Nullable): map table argument is NULL
onFetchFromServer
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) start
12.6.0 - [FirebaseFirestore][I-FST000001] Creating Firestore stub.
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) watch: <ListenRequest 0x7000052e1548>: {
  database: "projects/demo-123/databases/(default)"
  add_target {
    query {
      parent: "projects/demo-123/databases/(default)/documents"
      structured_query {
        from {
          collection_id: "users"
        }
        order_by {
          field {
            field_path: "__name__"
          }
          direction: ASCENDING
        }
      }
    }
    target_id: 2
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x70000546a5d8>: {
  target_change {
    target_change_type: ADD
    target_ids: 2
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x7000053e75d8>: {
  document_change {
    document {
      name: "projects/demo-123/databases/(default)/documents/users/nBWNES6LPP6NlDC5i7Vd"
      fields {
        key: "name"
        value {
          string_value: "Matt"
        }
      }
      create_time {
        seconds: 1765308073
        nanos: 432541000
      }
      update_time {
        seconds: 1765314956
        nanos: 427773000
      }
    }
    target_ids: 2
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x7000053e75d8>: {
  target_change {
    target_change_type: CURRENT
    target_ids: 2
    resume_token: "\n\t\010\351\305\205\334\266\261\221\003"
    read_time {
      seconds: 1765314966
      nanos: 676201000
    }
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x7000053e75d8>: {
  target_change {
    resume_token: "\n\t\010\241\306\205\334\266\261\221\003"
    read_time {
      seconds: 1765314966
      nanos: 676257000
    }
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) unwatch: <ListenRequest 0x7000053e7548>: {
  database: "projects/demo-123/databases/(default)"
  remove_target: 2
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x7000053e75d8>: {
  target_change {
    target_change_type: REMOVE
    target_ids: 2
  }
}
nBWNES6LPP6NlDC5i7Vd hasPendingWrites=false isFromCache=false ["name": Matt]
onFetchFromServer
nBWNES6LPP6NlDC5i7Vd hasPendingWrites=false isFromCache=false ["name": Matt]
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) watch: <ListenRequest 0x700005881a08>: {
  database: "projects/demo-123/databases/(default)"
  add_target {
    query {
      parent: "projects/demo-123/databases/(default)/documents"
      structured_query {
        from {
          collection_id: "users"
        }
        order_by {
          field {
            field_path: "__name__"
          }
          direction: ASCENDING
        }
      }
    }
    resume_token: "\n\t\010\241\306\205\334\266\261\221\003"
    target_id: 2
    expected_count {
    }
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) unwatch: <ListenRequest 0x700005882548>: {
  database: "projects/demo-123/databases/(default)"
  remove_target: 2
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x7000053e75d8>: {
  target_change {
    target_change_type: ADD
    target_ids: 2
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x70000546a5d8>: {
  target_change {
    target_change_type: RESET
    target_ids: 2
    resume_token: "\n\t\010\310\262\336\335\266\261\221\003"
    read_time {
      seconds: 1765314970
      nanos: 229064000
    }
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x70000546a5d8>: {
  document_change {
    document {
      name: "projects/demo-123/databases/(default)/documents/users/nBWNES6LPP6NlDC5i7Vd"
      fields {
        key: "name"
        value {
          string_value: "Matty"
        }
      }
      create_time {
        seconds: 1765308073
        nanos: 432541000
      }
      update_time {
        seconds: 1765314968
        nanos: 713493000
      }
    }
    target_ids: 2
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x70000546a5d8>: {
  target_change {
    target_change_type: CURRENT
    target_ids: 2
    resume_token: "\n\t\010\362\263\336\335\266\261\221\003"
    read_time {
      seconds: 1765314970
      nanos: 229234000
    }
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x70000546a5d8>: {
  target_change {
    resume_token: "\n\t\010\304\264\336\335\266\261\221\003"
    read_time {
      seconds: 1765314970
      nanos: 229316000
    }
  }
}
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) headers (allowlisted):
12.6.0 - [FirebaseFirestore][I-FST000001] WatchStream (313039353232333238) response: <ListenResponse 0x70000546a5d8>: {
  target_change {
    target_change_type: REMOVE
    target_ids: 2
  }
}

If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet 

{
  "originHash" : "c63c63846d9c539229e96de38d6af51417e28c0ee9a0bc48bd0f0f19d923c329",
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      "state" : {
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      }
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      "state" : {
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      }
    },
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      "state" : {
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      "kind" : "remoteSourceControl",
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      "kind" : "remoteSourceControl",
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If using CocoaPods, the project's Podfile.lock

No response

mattwiechec avatar Dec 09 '25 21:12 mattwiechec

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

google-oss-bot avatar Dec 09 '25 21:12 google-oss-bot