CODEWITHSUNDEEP
javascriptnode.jsfirebasegoogle-cloud-platformgoogle-cloud-firestore
Jaap Weijland
Jaap Weijland

Reputation: 3357

Firestore: Query by item in array of document

I have 2 collections "photos" and "users" and each document in "users" has one or more photo IDs with an array.

photos > 5528c46b > name: "Photo1"
         a1e820eb > name: "Photo2"
         32d410a7 > name: "Photo3"

users > acd02b1d > name: "John", photos: ["5528c46b"]
        67f60ad3 > name: "Tom", photos: ["5528c46b", "32d410a7"]
        7332ec75 > name: "Sara", photos: ["a1e820eb"]
        9f4edcc1 > name: "Anna", photos: ["32d410a7"]

I want to get all users who have one or more specific photo IDs.

Are there any ways to do that?

Upvotes: 43

Views: 43272

Answers (5)

Super Kai - Kazuya Ito
Super Kai - Kazuya Ito

Reputation: 1

With Firebase Version 9 (Dec, 2021 Update):

You can use "array-contains" with one single photo document ID in the "while()" to get all users who have it:

import {
  query,
  collection,
  where,
  getDocs
} from "firebase/firestore";

// Here
const q = query(
  collection(db, "users"),
  where("photos", "array-contains", "5528c46b")
);
// Here

const usersDocsSnap = await getDocs(q);

usersDocsSnap .forEach((doc) => {
  console.log(doc.data()); // "John's doc", "Tom's doc"
});

You can alse use "array-contains-any" with one or more photo document IDs with an array in the "while()" to get more corresponding users:

import {
  query,
  collection,
  where,
  getDocs
} from "firebase/firestore";

// Here
const q = query(
  collection(db, "users"),
  where("photos", "array-contains-any", ["5528c46b", "a1e820eb"])
);
// Here

const usersDocsSnap = await getDocs(q);

usersDocsSnap .forEach((doc) => {
  console.log(doc.data()); // "John's doc", "Tom's doc", "Sara's doc"
});

Upvotes: 1

ThinkDigital
ThinkDigital

Reputation: 3539

Firestore has now added an 'in' query as of November 2019. According to the announcement article:

With the in query, you can query a specific field for multiple values (up to 10) in a single query. You do this by passing a list containing all the values you want to search for, and Cloud Firestore will match any document whose field equals one of those values.

Upvotes: 1

Dan McGrath
Dan McGrath

Reputation: 42048

See Henry's answer, as we've no made Array Contains queries available.

Unfortunately not yet, although it's on our roadmap.

In the meantime, you'll need to use a map instead, in the form of:

photos: {
    id1: true
    id2: true
}

Now you can find all users with id1 by filtering by photos.id1 == true.

Read more about querying such sets in the Firebase documentation.

Upvotes: 34

Henry
Henry

Reputation: 32915

Added 'array-contains' query operator for use with .where() to find documents where an array field contains a specific element.

https://firebase.google.com/support/release-notes/js 5.3.0

Update: also available in @google-cloud/firestore: https://github.com/googleapis/nodejs-firestore/releases/tag/v0.16.0

Update 2 https://firebase.googleblog.com/2018/08/better-arrays-in-cloud-firestore.html

Update 3 now available in Admin Node.js SDK v6.0.0 https://github.com/firebase/firebase-admin-node/releases

Upvotes: 30

TheBen
TheBen

Reputation: 3520

Here is a bit of expansion on the answer as some seem to be confused about having to make indexes for each key, Firestore already indexes your data for simple queries thus you can do a simple query like 

documentReference.where('param','==','value').onSnapshot(...)

but you can not do a compound query unless you index your data for those parameters. So you would need indexes to be able to do something like this:

 documentReference.where('param','==','value').where(..otherparams...).onSnapshot(...)

So as long as you need the photos for an id you can save them as 

usersCollection :                        (a collection)
    uidA:                                (a document)
         photoField:                     (a field value that is a map or object)
            fieldID1 : true              (a property of the photoField)
            fieldID2 : true              (a property of the photoField)
            etc ...

and you can simply query user(s) that have, let's say, fieldID1 in their photoField without needing to form any index and like query below. 

firestore.doc('usersCollection/uidA').where('photoField.fieldID1','==',true).onSnapshot(...)

Upvotes: 5

Related Questions