XenForo Enhanced Search is an add-on that replaces the built-in XenForo search system and is built to take advantage of Elasticsearch to provide a higher performing and more flexible search system for XenForo.
In the beginning, XenForo Enhanced Search (XFES) was intended to be a simple drop-in replacement for MySQL full text search, primarily aimed at large forums whose operation would potentially suffer when attempting to search very large database tables.
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.
A useful tool for surfacing content on your forum is a list of Similar or related threads, which can be displayed along with a primary thread. Visitors who have landed on that page from a search engine will often look for related material to continue their reading, and Similar threads offer a great way to provide that in an automated fashion.
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.
Similar threads widget
We display our similar threads results in a widget, and by default we place it below the quick reply area on thread view pages, but as it is a widget you can choose to place it wherever you like on the page.