System.Data.SQLite VS SQLite

Instead of changing environment variables to modify the DLL search locations, I wanted to see if we can somehow provide an absolute path for the DLL location. Looking at the source for the NuGet package it's clear that, as the Microsoft Docs page noted, the C# code just invokes the native code (sqlite3_load_extension()) directly. Therefore I looked at the SQLite source code. SQLite has the concept of VFS which is a portability layer at the bottom of the SQLite architecture. There are implementations of this abstraction for specific operating systems. Windows and Linux implementations are os_win.c and os_unix.c respectively. The extension loading code eventually relies on VFS implementations to load DLLs. On Linux this is handled by dlopen and it's LoadLibraryW on Windows. I later rediscovered this same information after reading the bottom (section 7) of a SQLite documentation page.

If you are into alternative storage engines for SQLite, there is also an LSM (Log-Structured Merge-tree) extension in the main repository that is not announced nor documented but seems to work. It’s based on the SQLite 4 project.

https://github.com/sqlite/sqlite/tree/master/ext/lsm1

https://www.charlesleifer.com/blog/lsm-key-value-storage-in-...

The sqlite code base is really well done. Lots of documentation.

https://github.com/sqlite/sqlite

Especially the VM part: https://github.com/spandanb/learndb-py/blob/master/learndb/v...

Compare it with this: https://github.com/sqlite/sqlite/blob/master/src/vdbe.c

That's said, I'm curious how complete this LearnDB is. SQLite is hard to read not only it's old but also it covers a lot of SQL and following SQL spec makes hings complicated. SQLite has great test suite so it's nice if you run the suit against this implementation.

Correct, see the github mirror[1]. I don't know how well supported that feature is compared to main branch. If it was completely stable, then it would have already landed in the main stable branch. Clarity about the roadmap of that branch would be nice.

1. https://github.com/sqlite/sqlite/tree/begin-concurrent

Including comprehensive comments, documentation and tests in a codebase takes time and effort.

Failing to do so creates code that is very difficult to maintain or for someone new to the codebase to understand.

However, time and effort may not be what the organization wants to pay for, and individuals may view their own incomprehensible code as something like job security, as they can't be replaced by someone else easily.

As an example of complicated code that's still well-documented, the open-source sqlite code is a good example, about 1/4 of the B-tree file is comments, every time a variable is defined there's a short note explaining what it's used for, every function has a comment header that's comprehensive, such that someone new to the codebase could construct a map of how it all works fairly quickly. It's a good model for how to avoid the problem:

https://github.com/sqlite/sqlite/blob/master/src/btree.c