Determining unread items in a forum

Question

Using PHP and MySQL, I have a forum system I\'m trying to build. What I want to know is, how can I set it so that when a user reads a forum entry, it shows as read JUST for

Answer 1

The general ideas here are correct, but they've overlooked some obvious solutions to the scalability issue.

@bobince: The second problem is a combinatorial explosion. One row per user per topic soon adds up: just a thousand users and a thousand topics and you have potentially a million topicview rows to store!

You don't need to store a record in the "topicviews" table if somebody hasn't ever viewed that thread. You'd simply display a topic as having unread posts if null is returned OR of the last_read time is < last_post time. This will reduce that "million" rows by perhaps an order of magnitude.

@gortok: There are plenty of ways to do it, but each grows exponentially larger as the user visits the site.

In this case, you archive a forum after n-posts or n-weeks and, when you lock, you clean up the "topicviews" table.

My first suggestion is obvious and has no downside. My second reduces usability on archived topics, but that's a small price to pay for a speedy forum. Slow forums are just painful to read and post to.

But honestly? You probably won't need to worry about scalability. Even one million rows really isn't all that many.