how to delete document by field inside collection inside document inside collection on firestore - flutter

Question

I have Doctor collection when each doctor (represent by his email ) has a collection called patients_waiting.
Now, what I'm trying to do is delete one document from the paitents_waiting collection by field calls patients containing his email.
but I tried many solutions and none of them works for me now.
what I have tried to do :
Firestore.instance
.collection("Doctors")
.document(doctorEmail)
.collection("paitents_waiting")
.document(paitentEmail)
.delete();
now it's not good because the document is saved in uid and not by email but I tried to play with the where function but with no success.
how do I found this document by email and delete him?
I will mention that I'm doing it on flutter, but I think it doesn't matter.

Answer 1

as long as you have the patient's email address you can search with and delete it
Firestore.instance
.collection("Doctors")
. document(doctorEmail)
.collection("paitents_waiting")
.where('patient', isEqualTo:paitentEmail )
.get().then((value) => value.docs.single.reference.delete())
Nb: you are using an old version of firestore

Answer 2

Inside your paitents_waiting collection, the documents are NOT named according to patient email, they are randomly generated Firebase IDs. Take a closer look.
Firestore.instance
.collection("Doctors")
.document(doctorEmail)
.collection("paitents_waiting")
.document(paitentEmail) //this in your Firebase isn't an email, it's "xaErf43Asd..etc"
.delete();
If you want to follow this approach, which should be working otherwise, when you want to create a patient waiting document, use .set instead of .add, and set the document id to your pateint's email, like this:
Firestore.instance
.collection("Doctors")
.document(doctorEmail)
.collection("paitents_waiting")
.document(paitentEmail)
.set({your patient data here});
This should get things working for you.

Answer 3

To delete all patients for a doctor by the email you can use a combination of Firestore query and batch updates. The first one we need to get all patients with the same email and the other to delete them. A function for that would look like this:
Future<void> deletePatiensForDoctor(String docEmail, String patEmail) async {
WriteBatch batch = FirebaseFirestore.instance.batch();
QuerySnapshot querySnapshot = await Firestore.instance
.collection("Doctors")
.document(docEmail)
.collection("paitents_waiting")
.where('email', isEqualTo: patEmail)
.get();
querySnapshot.docs.forEach((doc) {
batch.delete(doc.reference);
});
return batch.commit();
}