AJAX long polling, increasing efficiency
<p>For a while I've been playing with the idea of long polling for my notification system, but i've never been able to think of a way to make it more efficient for my backend. </p>

<p>Most implementations I have seen hold the connection open, and the php queries the database server every few seconds to see if new data has been aded. This strikes me as no better than having the javascript repetitively poll the server. </p>

<p>In either case I have my database servers being hit tens thousands of times, which is understandably not particularly desirable. </p>

<p>Are there any systems in place that could 'alert' the executing/sleeping long polling script to the new data?</p>
