I want to notify users of changes on a site. Users are subscribed to different kinds of changes so I don't send all changes to all users.
Here's what I am thinking: at t=0 (i.e. an if statement that checks that some table is empty) I basically have an SQL query that fetches the appropriate changes and mails to the appropriate users. I then populate a user_changes table which essentially stores what changes have been mailed to what users. Mailing is done with the php mail function
Then at t>0, I run the SQL query again but this time with the condition that changes+user are not in the user_changes table. The main issue i see with this is that the user_changes table could get large very quickly. Is this a problem? I am trying to avoid hacks that use dates to filter stuff, since I want new users to be able to receive old changes that are relevant to them.
Appreciate suggestions.