@Override
 protected boolean matchDoc(int doc) {
   if (fieldsVisitorEnabled) {
     fieldsVisitor.reset();
     try {
       reader.document(doc, fieldsVisitor);
     } catch (IOException e) {
       throw Throwables.propagate(e);
     }
   }
   for (LuceneCollectorExpression expression : expressions) {
     expression.setNextDocId(doc);
   }
   Boolean value = condition.value();
   if (value == null) {
     return false;
   }
   return value;
 }