This short 2:37 minutes video shows it can be done.
How? I have no idea. Searched extensively online including Cloudera Documentation.
In fact, in the following Cloudera Search Webinar (under Cloudera Search Components: Part 2 --> upon clicking Next on Part 1), Impala is an optional component.
There is currently no built-in integration between Cloudera Search and Impala. I believe the video is showing off application-specific integration that Pentaho built.