install fts;  -- once should be enough

load fts;
create or replace table texts as (from read_text('inv*.txt'));

pragma create_fts_index(
   'texts',                      -- table name
   'filename',                   -- column name
   'content',                    -- column name of text
   stemmer = 'english',
   stopwords = 'none',
   strip_accents = 1,
   lower = 1,                    -- ignore case
   overwrite = 1);

# Simple interface to match_bm25 for conjunctive queries:
create or replace function s(queryString) as table (
  select filename,
         content,
         fts_main_texts.match_bm25( filename,
            queryString,
            conjunctive := 1) as score
  from texts
  where score IS NOT NULL
);