Add support for Firestore Collection Group queries #1284

Author: EddyVerbruggen

demo-ng/app/tabs/firestore/firestore.component.ts

@@ -398,8 +398,12 @@ export class FirestoreComponent {
   firestoreCollectionGroupQuery(): void {
     firebase.firestore().collectionGroup("cities").where("population", ">=", 1_000_000)
         .get()
-        .then(result => console.log(JSON.stringify(result)))
-        .catch(err => console.log("Delete failed, error: " + err));
+        .then(querySnapshot => {
+          querySnapshot.forEach(doc => {
+            console.log(`City with >= 1M population: ${doc.id} => ${JSON.stringify(doc.data())}`);
+          });
+        })
+        .catch(err => console.log("Querying collection group failed, error: " + err));
   }
 
   doWebGetValueForCompanies(): void {

docs/FIRESTORE.md

@@ -255,6 +255,23 @@ query
     });
 ```
 
+### [Collection Group Queries](https://firebase.google.com/docs/firestore/query-data/queries#collection-group-query): `collectionGroup.where()`
+A collection group consists of all collections with the same ID. By default, queries retrieve results from a single collection in your database. Use a collection group query to retrieve documents from a collection group instead of from a single collection.
+
+Note that this will require an *index* in your db, so make sure to `catch` any errors when invoking this method
+and log out any error messages so you can easily copy-paste the required index into your browser URL bar.
+
+```typescript
+// "Gimme all cities with a population of at least a million"
+firebase.firestore().collectionGroup("cities").where("population", ">=", 1_000_000)
+    .then(querySnapshot => {
+      querySnapshot.forEach(doc => {
+        console.log(`City with >= 1M population: ${doc.id} => ${JSON.stringify(doc.data())}`);
+      });
+    })
+    .catch(err => console.log("Querying collection group failed, error: " + err));
+```
+
 ### Delete an entire document: `collection.doc().delete()`
 Entirely remove a document from a collection:
 

docs/STORAGE.md

@@ -212,9 +212,6 @@ In this example we'll determine the remote URL of the previously uploaded file.
 Note that your security rules must be version "2" for this to work,
 so if it fails try adding this at the top of your rules defined for your storage bucket: `rules_version = '2';`
 
-Also note that this will require an index in your db, so make sure to `catch` any errors when invoking this method
-and log out any error messages so you can easily copy-paste the required index into your browser URL bar.
-
 <details>
  <summary>Native API</summary>
 
@@ -230,7 +227,6 @@ and log out any error messages so you can easily copy-paste the required index i
           // see the Web API example below for an advanced example
       },
       function (error) {
-          // probably related to a missing index or security rules, see the notes in the readme above
           console.log(error);
       }
   );