Do you use full text search with SPARQL? If so how and why?

I noticed that from the thread on What's missing from RDF databases? that one thing people were quite keen on was full-text search in SPARQL.

This is because it mitigates a classic alleged performance problem in SPARQL when people write queries like so:

  ?s ?p ?o 
  FILTER(REGEX(?o, "substring"))

It should be self evident that writing a query like this is a bad idea because you get a huge swathe of potential matches and then have to apply a regular expression on every one. Full text search extensions to SPARQL let you write queries which achieve the same thing with huge performance advantages, for example the LARQ style syntax:

PREFIX pf: <>
    ?lit pf:textMatch 'substring' .
    ?s ?p ?lit

However one problem with this is that is isn't standardised and every vendor seems to have different syntaxes for this, I'm aware of at least 3 different implementations none of which are interoperable:

So I wondered several things:

  1. Are you using full text search with SPARQL or would you use it if it were available in your RDF database/SPARQL engine?
  2. Whose implementation do you use? Please add links to documentation and an example if it's not one I've listed or someone else has already suggested
  3. What's your use case for it?

I'm particularly interested in point 3, maybe I'm being unimaginative but I can't think of any use cases beyond the glaringly obvious text search uses i.e. using it to find RDF graphs/triples containing certain text. If you have some other interesting/useful use case please enlighten me!