Firestore 读取、写入和删除如何计算？

Question

I'm not sure if I understand Firestore reads, writes, and deletes correctly. I think the best way I would understand is if I got clarification, correction, or answers of the total reads, writes, or deletes per action on the following questions below. I'm using Next.js

Q: If I add collection with document no matter how many fields , does it count as 1 write, or does it count how many collection , documents , and total fields we wrote? And is it the same logic for reading and delete?

Current setup for a project:

LOGIN

I'm currently using Google sign-in provider as sign-in method.

Everytime a user logs in useEffect renders and setDoc on "Users" collection , user.uid document :

user: {
  //Default Firebase Authentication info
}

The header component(outside of layout) is then updated with:

user.photoURL

user.displayName

Q: How many reads and writes for every time a user logs in?

POSTS

On HomePagePosts component(inside layout) 10 recent posts are fetched from "Posts" collection . Every post include:

user.photoURL
post.title
post.description
post.createdDate
postURL.postID

If currently, a logged-in user created any of the 10 posts, an edit & delete button is shown. For my question, let's say 2 of the posts were created by currently logged-in users.

Q: How many initial reads for the 10 posts?

CREATE POST:

When user goes to createpost page useEffect renders and checks if "Posts" collection , user.uid document , "Folder" collection .length > 0.

If Folder length not greater than 0, CreateFolder component displays, it includes:

folder.name

folder.type //local JSON file

When a folder is created its added to "Users" collection , user.uid document , "Folders" collection , then useEffect renders again.

If Folder length greater than 0, Folder component shows a list of folders.

When user creates the post document is added to "Posts" collection with:

post.title
post.description
post.content
postCategory.selectedFolder.type
folder.{
  folder.name
  folder.type
}
tags.{
  (lets say 2 tags)
}

Q: How many reads and writes for 1 post created and 1 folder created within?

Answer 1

It doesn't really matter how many fields an object has, when you perform a write operation in Firestore, you'll have to pay a single write. This works only if the rules allow that write and only if the document is within the 1 MiB limit, otherwise will fail. The same rule applies to the reads and deletes you perform.

If you want to reduce the costs, you might be interested in reading this article:

• How to reduce Firestore costs?