What's the best way for the client app to immediately react to an update in the database?

Question

What is the best way to program an immediate reaction to an update to data in a database?

The simplest method I could think of offhand is a thread that checks the databa

Answer 1

I figure there must be some way, after all, web application like gmail seem to update my inbox almost immediately after a new email was sent to me. Surely my client isn't continually checking for updates all the time. I think the way they do this is with AJAX, but how AJAX can behave like a remote function call I don't know. I'd be curious to know how gmail does this, but what I'd most like to know is how to do this in the general case with a database.

Take a peek with wireshark sometime... there's some google traffic going on there quite regularly, it appears.

Depending on your DB, triggers might help. An app I wrote relies on triggers but I use a polling mechanism to actually 'know' that something has changed. Unless you can communicate the change out of the DB, some polling mechanism is necessary, I would say.

Just my two cents.