As a drop-in, XFES only made use of the enhanced search index and speed for the formal search system, but with version 2.2 we are starting to leverage more of the power afforded by the Elasticsearch back-end.
One limitation of the usefulness of Similar threads is a determination of just how similar or related the results actually are. This is where XFES comes into its own, as the Elasticsearch back-end provides a specific ability to search for more like this using the current thread as a search parameter. Given a decent amount of content from which to pluck similar results, this provides an excellent list of threads in which the viewer of the current thread may be interested.
You could even choose to place multiple instances of the widget on the page, and make use of the power of the widget system to control how each instance of the widget behaves, setting parameters such as the number of thread results visible, the style of display, the source forums searched and the time period within which to search.
But wait, there's more...
The extreme speed and efficiency of XFES allows us to offer another, related tool to our arsenal: similar thread suggestion at thread composition time.
XFES 2.2 aims to minimise the occurrence of this, by suggesting related threads that may contain content similar to that which the user is about to post, while they are composing. XFES is fast enough that sensible suggestions can be made in real-time while the user is typing the title of their new thread, which may prompt them to visit one of the suggested existing threads rather than posting a potential duplicate.
The thread suggestion system can be a real game-changer for unwanted duplicate threads.
The system can be turned on and off through the control panel, along with options for how many similar threads to suggest.
It's also possible to prevent the suggestion system from appearing at all on a per-forum basis. For example, we would never want to be pestered with suggestions for similar threads when composing a new release announcement, or a Have You Seen thread.
By way of a reminder, XFES requires that your server has Elasticsearch 2.0 or newer, and can be purchased here.