Show HN: sqlite-memory-vfs - Open a SQLite db in Python without hitting disk

It looks like memory is also not contiguous in your implementation.

You don't support concurrency at all (xLock/xUnlock/xCheckReservedLock are noops).

I'm not sure how APSW handles journaling (you usually want the journal_mode to be memory in these cases, but to force that, you must return SQLITE_OPEN_MEMORY as an OutFlag from xOpen). Otherwise, you need to deal with files (like journals, etc) for which reads/writes are not page aligned.

There is one caveat, though: if you want to “deserialize” a WAL database with journal_mode memory, you must convert it to rollback before opening (but you can do that by editing bytes 18 and 19).

In terms of the difference from pointing SQLite to /dev/shm, my answer is somewhere between "I don't know", and "I suspect the VFS is more portable because not all systems have /dev/shm?"

While SQLite supports the special filename :memory: that allows the creation of databases in memory, there is no built-in way to populate such a database using raw bytes without hitting disk as an intermediate step. This virtual filesystem overcomes that limitation.