Keeping track of unread forum posts

[KrazyWebGuy]

For some time I have been toying with the idea of creating my own forum. The concept is fairly simple, but I keep getting hung up on one feature: being able to see unread posts. Posts would be stored in a MySQL database, and I could easily make a page that shows the posts made since a user's last visit (by updating a timestamp everytime a page is accessed and comparing it with a post's timestamp), but that would only work on the first page load of the user's new visit. After that point, the user's "last activity" timestamp would be updated, and posts made after the user's previous visit which have not yet been read would no longer be displayed.

So my question is, what is the best way to keep track of individual posts that have not yet been read? I came up with several idea, such as having a field in each post's MySQL row that includes all the usernames of the users that have viewed the post, or a cookie that includes the post IDs of all the posts the user has viewed. The problem is that both of these methods are terribly inefficient (especially the first one).

Does anyone know how popular forums accomplish this task?

Any information would be helpful 🙂.

-KrazyWebGuy

[dagon]

new table called posts_read

post_id | user_id |timestamp (optional)

[KrazyWebGuy]

Thanks for the tip, that's a lot more convenient than my method. I think I will vary it a little bit so it's not adding a row for every user AND every post, and make it like this:

user | topic | last post user has read in topic

That way I just have one row for each topic for every member. I can do a check to see if the last post in a topic exceeds the one listed for a particular member 🙂. This also gets rid of the problematic timestamp comparison, while still being able to keep track of a user's last activity.

Thanks,
KrazyWebGuy