Database Design - “Push” Model, or Fan-out-on-write

问题

Background Info :

I'm trying to retrieve images from people I follow, sort by latest time. It's like a twitter news feed where they show the latest feed by your friends.

Plans:

Currently there is only 1 item i need to keep in consideration, which is the images. In future i'm planning to analyse user's behavior and add in other images they might like into their feed, etc.

http://www.quora.com/What-are-best-practices-for-building-something-like-a-News-Feed

I personally feel that "Pull" Model, or Fan-out-on-load where i pull all info at real time would be worst than the push model. Because imagine i have 100 following, i would have to fetch and sort by time. (Let me know if i'm wrong eg, Read is 100x better than Write(Push Model)

The current design of the push model i have in mind is as follows

Table users_feed(ID, User_ID, Image_ID,datetime)

Option 1 : Store A list of Image_ID

Option 2 : Store one image ID and duplicate rows(More Rows of same User_ID but different Image_ID)

The plan is to limit each Row a user can have in this feed , which means , there would always be a max of 50 images. If they want more items beyond the 50 images in their news feed. They cant(I might code a alternative to store more so they can view more in future)

Question 1

Since when user following users add a item into their "collection" i have to push it into each of their follower's feed. Wont there be a problem in Write? 200 followers = 200 writes?

Question 2

Which method would be better for me keeping in consideration that i only have one type of data which is images. Feeds of images.

Question 3

If i choose to store the feed in advance(push method) how do i actually write it into all my friends?

Insert xxx into feeds whereIn (array of FriendsID)?

Any form of advice would be greatly appreciated. Thanks in advance!

回答1:

I would recommend you to follow pull method over push method for the following reasons:

• It gives to more freedom for extencibility in the future.

• Less number of writes ( imagine 10M followers then there has to be
  10M writes for just 1 post).

• You can get all feed of a user simply by query similar to:

  SELECT * FROM users_feed as a WHERE a.user_id in ( < //select all user_ids of followers of loged in user// > )

  (Syntax not followed as table structure of followers is not known)

来源：https://stackoverflow.com/questions/21833650/database-design-push-model-or-fan-out-on-write