Tianchi competition, transfer DB data https://tianchi.aliyun.com/competition/entrance/531896/introduction
The master branch is deprecated because it is so slow. But lately, I found it is the inefficiency of the C++ regex library that leads to it.
So, branch refined is a faster implementation with adjustment of data structures and with mmap. It can be further optimized with pmem library according to the competition, but I do not have enough time to finish it.