Number of concurrent users range from tens and rarely hit hundreds. SQLite can handle that kind of traffic without any issues.
Pretty much one of the classic desktop support calls for me was "my access database on the shared drive is corrupt"
I'm out touch now, but one of the failure modes seemed to be that a client would take out an oplock, so it could do local caching etc. Then someone else opens the file, the server sends the oplock break to original client but that message gets lost/ignored, and we end up with 2 or more clients now making unsynchronised changes to a file.
Any smb client access to shared data more complicated than documents and spreadsheets just makes me twitch these days.
It was a long time ago now, and it probably was more prevalent in larger environments.. just more chances for things to go wrong I'd guess.
If something is designed for shared filesystems that's different, but my experience was that at the low midrange things aren't. They seem to work, until they don't.
What's wrong with sql express? Assuming you fit within its size constraints?
Yes, that one >12 year old access database with two concurrent users brakes biweekly. Everything else: No problems.
Just this Thursday I "moved" a program from an old PC to a new one. We more or less support this client since 7 years. The PC is from before that. Got the call. First time hearing about that lab software. Right click on the desktop icon. Oh, it just points to an UNC path on the "main server" (Linux Samba share). Took a look into the settings. It has a path to a SQLite DB. Also just an UNC path. Only two clients using it. It worked unattended for years. Since it's stored on the "main server" it's also covered by backup. No client side installation necessary. Copy the link. Update our documentation that we know it exists, what is it used for and how it works. Done.
I see it time and time again: Desktop software that runs on one PC, produces/saves tiny amounts of data (like a temperature monitor for one fridge), but installs a SQL server. A random technician shows up, installs it and leaves. We don't know that it exists. It's therefore not part of a backup concept. It's usually only discovered when it explodes or when the PC is renewed (or when a second PostgreSQL install creates a TCP port conflict). I have the feeling only 1 out of 10 "softwares" even have a proper concept for export and import of data.
A client with like 7 or 8 workers called my because he wanted me to move his new time tracking software. The technician who also installed the NFC reader apparently installed it on the wrong PC. It took over 3 hours! It downloaded GBs and GBs of .NET, SQL Express and what not. I didn't know that going in/clicking the setup.exe. I had to call support to get the Express DB over. I can still hear the hard drive screaming. ...man... for stuff a Z80 and a CSV file would be enough. ...And I am the bad one for explaining to the client that the DB needs to be backuped. I sound like I want to upsell him something.
I know, I know. This rant is not about databases. It's about the state of IT and arrogant developers who don't live in the trenches. The "pulling down additional gigabytes of images and runtime to run the database" > "Yes. It works great." triggered me. I'm sorry. You know. Not everything is a unicorn webapp.
> Any smb client access to shared data more complicated than documents and spreadsheets just makes me twitch these days.
I know of multiple large install bases of an old medical software. It's still actively developed/supported but it is so old that it doesn't use a SQL but ISAM database. It just lies there, on a file share. No active server component to speak of. No client site installation necessary.
> What's wrong with sql express? Assuming you fit within its size constraints?
If it is not used for something a CSV file would be enough. If the costumer is told that it needs to be installed "on a server". If we get involved from the beginning so we know what is what. If the costumer doesn't expect me to be able to move it out of the blue within seconds. Than sql express is fine. ...which reminds me of that one time, when that well-hung developer of a software for the energy sector didn't knew that express only can allocate up to 2GB. Obviously he was blamed us for delivering a faulty server...
I can really recommend it, using a declarative docker-compose.yml file and then docker-compose command.
If you have a single process accessing the database, use SQLite. If not, use Postgres.
This means SQLite is very much locked to things that works with one specific purpose and almost nothing else. Sure, you can be read-only, but you have to run alongside the app in the specific node, too.
Another problem (although without solving the single user mindset this wouldn't be a problem at all) is high availability. You want to make sure that your database won't get lost do you.
Things like Litestream [1] attempts to solve the SQLite backup problem it by continuously saving the database state and pack t up to S3-compatibles or file system but its just half the story. You want to make sure your operation not stopping. This is where HA comes in to save you from an emergency fixup when you are enjoying your holiday.
It doesn't mean that nobody tried to solve both these problems though. Ahem, introducing rqlite [2]. Although my own experience is not very great because the memory usage is quite high and does not fit my need (because the embedded device only has 512MB on it, and every byte counts, sorry), I guess that's the price to pay if you want to turn a non-multiuser, non-concurrently acccess database into one...Another honorable mention would be LiteFS [3] but I haven't used it yet so I have no say on it.
[1]: https://litestream.io/
[2]: https://github.com/rqlite/rqlite
[3]: https://github.com/superfly/litefs