mvsqlite VS dflat

- Oh, and if you're wondering about backup to S3, they have that too: https://github.com/libsql/bottomless

- Uh, sqld can integrated with this https://github.com/losfair/mvsqlite, so now your SQLite is backed by FoundationDB!?

- Meanwhile Litestream exists https://github.com/benbjohnson/litestream/

This was on HN a few months back: https://github.com/losfair/mvsqlite

While not Spanner, it is essentially an open source db like AlloyDB or Aurora, pushing replication and scale out to the storage layer (in this case via FoundationDB). The most interesting bit of mvsqlite is it's multi-writer capabilities, using FoundationDB to perform page-level locks.

I'm neither the creator nor using it in production, but I'd love to see more DBs using FoundationDB as storage. It's a pretty cool solution.

Shameless plug of my [mvSQLite](https://github.com/losfair/mvsqlite) project here! It's basically another distributed SQLite, but with support for everything expected from a proper distributed database: synchronous replication, strictly serializable transactions, + scalable reads and writes w/ multiple concurrent writers.

The approach to edge-ifying SQLite taken in [1] looks quite promising - using FoundationDb as the storage handles a lot of hairiness.

1: https://github.com/losfair/mvsqlite

This project looks really exciting!

I'm working on mvsqlite [1], a distributed SQLite based on FoundationDB. When doing the VFS integration I have always wanted to patch SQLite itself, but didn't because of uncertainty around correctness of the patched version...

A few features on my wishlist:

1. Asynchronous I/O. mvsqlite is currently doing its own prefetch prediction that is not very accurate. I assume higher layers in SQLite have more information that can help with better prediction.

2. Custom page allocator. SQLite internally uses a linked list to manage database pages - this causes contention on any two transactions that both allocate or free pages.

3. Random ROWID, without the `max(int64)` row trick. Sequentially increasing ROWIDs is a primary source of contention, and causes significant INSERT slowdown in my benchmark [2].

[1] https://github.com/losfair/mvsqlite

[2] https://univalence.me/posts/mvsqlite-bench-20220930

That DynamoDB VFS looks cool! I agree that the VFS api makes one think about plenty of crazy ideas. Someone is working on a VFS based on Foundation DB[0] that looks very promising. It was recently discussed here[1]

[0]: https://github.com/losfair/mvsqlite

[1]: https://news.ycombinator.com/item?id=32269287

Hi mrkurt!

Litestream/LiteFS are amazing projects. The FUSE-based approach is interesting (I'm implementing something similar in mvSQLite, thanks for the idea!)

> Graceful failure

mvSQLite is designed to continue to operate under degraded network (there is a fault-injection test specifically for checking this property: https://github.com/losfair/mvsqlite/blob/1dd1a80d2ff7263b07a...). Network errors and service unavailability are handled with idempotent retries and not exposed to the application.

> Good for caching

mvSQLite caches pages read and written, and does differential cache invalidation (only remotely modified pages are invalidated in the local page cache). The local cache is just a regular KV store with invalidation strategies, and can be moved onto the disk. So it essentially becomes a consistent local database snapshot.

Came over this article as I was looking for interesting resources in the SQLite ecosystem. I'm building mvsqlite (https://github.com/losfair/mvsqlite), as an attempt to turn SQLite into a proper distributed (not just replicated) database. Check it out if you are looking for this kind of stuff!

There's a page in the wiki doing the comparison: https://github.com/losfair/mvsqlite/wiki/Comparison-with-dql...

This is really, IMHO (as someone implements things on top of SQLite too https://dflat.io) pushes SQLite too far as the implementation of cross-db transactions have some big issues: https://www.sqlite.org/limits.html (the number of attached databases cannot exceed 10 or 125 (if you compile your own)) https://www.sqlite.org/wal.html (in WAL mode, there is no transactional guarantee for cross database transactions (atomic per database, but not cross database))

Dflat: SQLite FlatBuffers\ (4 comments)

Flatbuffers would be better as it doesn't need to deserialize at all (I think protobuf supports to partially deserialization nowadays?). I did something similar with https://dflat.io/ too!