I have finished the lab(MIT 6.830) and passed all the tests in the "test" directory.
Most "Extra Credit" functions are not implemented.
https://github.com/CreatorsStack/CreatorDB
https://blog.csdn.net/weixin_45938441/article/details/128729077
However, I have found that both of their implementations fail to pass all the tests. So be careful if you want to refer to the links above.