I'm using ES2.0 and have a field mapped with "term_vector": "with_positions_offsets". Using a "span_multi" query, I get no highlighting information back when using "fvh". However, forcing the highlighter to "plain" works. Is this an expected limitation of FVH?
The reference documentation provides a warning for the "postings" highlighter that it may not work with certain complex searches, but I don't see any limitations mentioned for FVH.
The documentation indicates the plain highlighter can suffer from poor performance under certain situations and was hoping to use FVH instead, though I have no real-world benchmarks as we're only in the proof-of-concept stage.
Its a known limitation, yes. It doesn't support span queries. Indeed its a defect in the documentation. Highlighting in general is a best effort kind of thing and there are lots of "fun" things to find like this.
If you were on 1.7 you can try the experimental highlighter that I wrote when I worked for Wikimedia. Its in use there but no one has upgraded it for 2.0. I should really do that..... Anyway, it makes an effort to smooth away some of the rough edges around highlighting. It solves more problems than it introduces and its been in use at WMF for a while now and has been stable and fast.