: I haven't looked at this specific code, but this is my preference in : general. multiple TokenFilters are created per-field instance on the : index side, and per-query-term on the search side, so it's better to : pull all the setup you can out of the Filter for performance reasons.
computation can be done at factory instantiation, but it can make sense to put the code for the computation in static methods within the Filter class itself -- so it's more reusable outside of Solr. -Hoss
