Some final notes about LMDB review
Okay, having gone through the LMDB codebase with a fine toothed comb, I think that I can safely say that it is both a very impressive codebase and one the dearly need some TLC. I’ll freely admit that I am by no means a C guy. And it is entirely possible that a lot of the issues that I have been bugging me are standard C things. But I don’t think so. Methods that go on for hundreds of lines, duplicated code and plethora of gotos hardly seem to be the things that pop to mind when I hear good C code.
But beyond my issues with the code, the implementation is really quite brilliant. The way LMDB manages to pack so much functionality by not doing things is quite impressive. Interestingly, you couldn’t write this database even 5 years ago. LMDB relies on being able to map the db into memory, and up until x64 became prevalent, you just couldn’t do that for any db with a meaningful size. With x64 and the effectively unlimited address space we have (will I be laughing at my naivety in a few years?), that is no longer an issue.
I learned quite a lot from the project, and it has been frustrating, annoying and fascinating experience.