code: private List<Bucket> lookup(Record record) {
      List<Bucket> buckets = new ArrayList();
      for (Property p : config.getLookupProperties()) {
        String propname = p.getName();
        Collection<String> values = record.getValues(propname);
        if (values == null)
          continue;
  
        for (String value : values) {
          String[] tokens = StringUtils.split(value);
          for (int ix = 0; ix < tokens.length; ix++) {
            Bucket b = store.lookupToken(propname, tokens[ix]);
            if (b == null || b.records == null)
              continue;
            long[] ids = b.records;
            if (DEBUG)
              System.out.println(propname + ", " + tokens[ix] + ": " + b.nextfree + " (" + b.getScore() + ")");
            buckets.add(b);
          }
        }
      }
  
      return buckets;
    }
docs: Tokenizes lookup fields and returns all matching buckets in the
  index.