Sorry its meant to mean the scoring index which is provided by elasticSearch. using filter stops any scoring on the index and caches the subset. Hopefully this makes sense, I can go over the work again if you think it may help comprehending its meaning.
![screen shot 2013-07-02 at 10 09 59](https://f.cloud.github.com/assets/3082998/739495/e92d0246-e35b-11e2-874b-fbd4b74efb05.png)