void continue_sample_iteration(SegmentDataIterator* it, uint64_t increase);
void end_sample_iteration(SegmentDataIterator* it);
uint8_t* get_iterator_value(SegmentDataIterator* it);
+ uint64_t get_iterator_valid_length(SegmentDataIterator* it);
uint32_t segment_id_;
mutable recursive_mutex mutex_;