是否可以从父集合（Firebase Cloud Firestore）访问子集合？

Question

I have a collection like bellow:

db.collection("col1/doc1/col2/doc2/col3/doc3/col4").get();

Now I have to get all collection collection2 and collection4

With my current know knowledge I have to get them separately like bellow:

db.collection("col1/doc1/col2").get();

and

db.collection("col1/doc1/col2/doc2/col3/doc3/col4").get();

My expectation is I want to call it at once with collection2

db.collection("col1/doc1/col2").get().then(snapshot=>{
   //here something like snapshot.col3.col4
});

Is it possible like snapshot.col3.col4 ?

Why I want like this ?

Because I will not have to call it more than one time from server, may it increase performance and make it faster.

Answer 1

Is it possible like snapshot.col3.col4?

No, it's not. Queries in Firestore are shallow, which means that only get items from a collection that the query is run against. There is no way you can get documents from a top-level collection and a subcollections with different names in the same time. Firestore doesn't support queries across different collections with different names in one go. A single query may only use properties of documents in a single collection.

A possible solution for your issue might be the use of Collection group queries , but as the doc states, all collections should have the same name.

Another workaround might be, to create two separate queries and merge the result client side. For that I recommend you see my answer from the following post:

• Firestore - Merging two queries locally