javascript - 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!

question from:https://stackoverflow.com/questions/49483406/firestore-get-specific-fields-from-document

Answer 1

Waitting for answers