使用Redis的新闻提要

Question

I have the following table structure where I am storing activity of a user like 'product creation'

id user_id type_id type verb data created_at updated_at

Whenever an event happens on a product like ( an order has come for the product), I need to update the updated time, so that the record appears in the first as the user will be seeing the 'sorted using updated_at' row data. The feed which I am referring here will be consumed by a single user and there is no concept of following here. So whoever created a feed will be seeing his own feeds. If there is an update (order placed by someone on that product) coming on the feed, it should go up.

So when an order is placed, I will update the updated time of the entry so that it appears in the first.

I am planning to use redis for the reads, but I am pretty confused on the update part. How will I handle this case.

What I have tried ?

Created the table structure as following

1. id
2. user_id - User who created the event
3. event - created_product
4. event_id - product_id of products table
5. data - json object of the product details
6. created_at
7. updated_at

When an order is received

The updated_at timestamp is updated. So that the record comes on the top of the user feed.

But this doesn't seem to be a proper solution as frequent updates can come for a row which can lead to row locking and more waits. How do I solve this?

Answer 1

Well, you could create sorted set in redis:

FEED:USER_ID containing values:

PRODUCT_ID - last update time as score

And then get products from database by ids which you got from redis.

But if your main concern is row locking, then maybe you should just queue updates? Create redis sorted set "PRODUCT_UPDATED" and add row whenever you are updating product:

USER_ID#PRODUCT_ID - update time as score

Then create some background CRON job which will update products found in that sorted set. You can do it every second, or every 30 seconds, you can throttle number of updates etc...