Method empty

tools/cdb2_sqlreplay/cdb2_sqlreplay.cpp:964–970

    }

    bool empty() {
        for (auto &i : sources) {
            if (!i.is_done())
                return false;
        }
        return true;
    }
    cson_value *get() {
        int64_t min_timestamp = LLONG_MAX;
        int minix = -1;