firebase - Why are there so many READ operations with a function that loads a single document?

Question

I am building a Flutter application that loads a document from Cloud Firestore and displays its content in a BottomSheet widget.

The read is performed on a collection (named details) that has almost 4K documents in it. Also, each document has a complex JSON, where the requested data is. This JSON has 2 simple Map objects, one array and up 10 Strings.

I want to read a single document from details for displaying it on the BottomSheet, so I request the desired document with an specific given id in initState(), upon the creation of the BottomSheet.

// CustomBottomSheet Widget

CustomData info;

@override
void initState() {
    _getDocument();
    super.initState();
}

Future<void> _getDocument() async {
    final FirebaseFirestore _fireStoreReference = FirebaseFirestore.instance;
    try {
        await _fireStoreReference.collection("details").doc(widget.uid).get().then((snapshot) {
            if (snapshot != null && snapshot.exists) {
                setState(() { 
                    // fromJson is a factory method from CustomData to translate
                    // the Map<String, dynamic> from Firebase into a 
                    // CustomData Object
                    info = CustomData.fromJson(snapshot.data());
                });
            }
        });
    } catch (err) {
        //...
    }
}

@override
Widget build(BuildContext context) {
    return BottomSheet(
        onClosing: () => {},
        builder: (context) {
            return Container(
                child: // Display data of CustomData
            )
        }
    );
}

// CustomBottomSheet Widget is called from the Main Page as so

...
GestureDetector(
    onTap: () async {
        await showModalBottomSheet(context: context,
            isScrollControlled: true,
            backgroundColor: Colors.transparent,
            isDismissible: false,
            builder: (context) {
                return CustomBottomSheet(uid: "0001");
            }
        ).then((_) { 
            // Uploads some UI when BottomSheet is closed
        });
    },
    child: Container(width: 150, height: 90, color: Colors.orange, child: Text("Show Data"))
),
...

This query should cost only 1 READ operation, but whenever I show the BottomSheet, Cloud Firestore charges me with +7K READ operations. This morning I went from having 619 reads to 8.2K reads only after requesting a single document of "details".

My thoughts were that I was somehow requesting it that many times or perhaps that the JSON inside each document is so complex and large that it costs exactly that amount of READ operations each time I request it. With these things in mind, I searched for answers, but everywhere I read says that reading one document, no matter what is inside, it will cost 1 READ.

I also debugged the application and, as expected, initState() is only called once and therefore, the document is read only once on execution, so I do not know from where these insane amounts of READ operations come from.

Furthermore, it came into my mind that just looking up the 4K documents inside details on the Firebase Console maybe is correlated to the problem, as you are requesting the reading of those documents as you scroll by them. But I do not know.

question from:https://stackoverflow.com/questions/65873979/why-are-there-so-many-read-operations-with-a-function-that-loads-a-single-docume

Answer 1

Basically the READ operations are being charged within the Firebase Console. So, if I request from the app a document, the expected READ operations will be charged. But if I enter the Firebase Console and scroll thorugh all documents, the charges skyrocket.