Firestore - get specific fields from document

Question

What I need:

I want to save articles or notes in Firestore with their respective fields:

• Title
• Content (texts or paragraphs)
• Creation date
• Owners (to share that article with other people and who can edit them like: https://firebase.google.com/docs/firestore/solutions/role-based-access)

But when I show the list of articles I don't need the "content" field (to save bandwidth). I've read that (maybe I'm wrong), it is not possible to make a query to get only specific fields from a document with Firestore.

If it were normal SQL to obtain specific columns from articles (without its content) It would be something like:

SELECT title, creation_date, ... FROM table_name; 

So I've opted to separate the content for two root-level collections (for flexibility and scalability)

---

My current structure:

Articles collection:

  - `articles` [collection]     - `ARTICLE_ID` [document]       - `creatorId` [field]       - `title` [field]       - `date` [field]       - `owners` [obj field]           - {user1_id}: true           - {user2_id}: true           ... 

Contents collection:

  - `contents` [collection]     - `{ARTICLE_ID}` [document]       - `content` [field] 

To get articles list in realtime:

firebase.firestore().collection('articles')   .where(`owners.${user.uid}`, '==', true)   .onSnapshot(querySnapshot => {     const articles = []     querySnapshot.forEach((doc) => {       articles.push({         id: doc.id,         ...doc.data()       })     })     // do something with articles array   }) 

To show in another view and get the entire article with its content:

const db = firebase.firestore() const articleRef = db.collection('articles').doc(articleId) const contentRef = db.collection('contents').doc(articleId) // same Id as article  articleRef.get().then(articleDoc => {   if (articleDoc.exists) {     contentRef.get().then(contentDoc => {       if (contentDoc.exists) {         const article = {           ...articleDoc.data(),           ...contentDoc.data()         }         // full article obj       }     })   }  }) 

---

My questions

• Do you think it's better to do two queries (getArticle and getContent) at the same time and wait with Promise.all() instead of nesting the querys like I do?

• Is there a better way to get the article and its content with one query or more efficiently? Some tips or ideas?

Thank you very much in advance!

Answer 1

According to the Firestore Query.select documentation you should be able to select the fields you want.

let collectionRef = firestore.collection('col'); let documentRef = collectionRef.doc('doc');  return documentRef.set({x:10, y:5}).then(() => {   return collectionRef.where('x', '>', 5).select('y').get(); }).then((res) => {   console.log(`y is ${res.docs[0].get('y')}.`); });