If you're going to use serialisable isolation level, why bother using a traditional RDBMS at all? At that point you're better off using a simpler datastore.
Pretending like redis is suitable for an RDMS workload because it executes things serially means you’re completely ignoring what transactions are actually used for and how they work.
On the contrary, you have Lua which is much more expressive than SQL (yes Turing completeness, but there's a huge difference in how easy it is to read and understand).
> Pretending like redis is suitable for an RDMS workload because it executes things serially means you’re completely ignoring what transactions are actually used for and how they work.
Well the vast majority of RDMS workloads don't use serial isolation, that's part of my point. As for the rest, all I can say is I've worked on many systems in many industries and seen very few (honestly none) that actually made effective use of what transactions do and don't give you.
SSI gives you the performance of close to snapshot isolation with the safety of serializability. The lowest I would ever go is snapshot isolation and ideally SSI. Anything else I’d use an eventually consistent database instead because then there’s at least no pretense.
but ignoring that, serializable isolation level means the database acts AS IF the transactions are serial. but most databases in fact will execute them concurently, with careful tracking to make sure they appear serial
Sometimes though, yes definitely. It's hard to claim anything universal at all about databases.
(Unless you mean "being able to choose between different isolation levels", then yes, completely agreed. Very very few use anything but the default, somewhere below serializable, and it always concerns me unless they can describe exactly what they're intentionally allowing and why it's okay for their system. Most cannot.)
But you usually don't need serializable for this, cause READ COMMITTED locks the rows during updates.
Big point: Serializable not exist alone in a decent ACID datastore, and no, less strict rules for the MOST important thing you have(your data) is NOT a good idea.
Over and over again Acid RDBMS have proven that trying to "relax" the rules in pursuit of performance or worse, mystical holy grails that have never been right or correct for a primary datastore, is a mistake. And then people goes back to them, because is the best tool for ALL the primary data store jobs. ALL OF THEM.
Is like the mythical C developer that "not need safety", that at least has more chance of be possible (after MANY passes over the code) that a datastore without safeguards.
On the contrary. The most successful RDBMS by far was MySQL in an era where it didn't have any kind of ACID (you could write the transaction keywords but they didn't do anything). As the story we're talking about now shows, RDBMSes are routinely deployed with transaction settings that their users don't understand, much less use; there are settings that would reduce bugs if anyone cared to use them, but no-one does. People cargo-cult the idea that they should be using an Acid RDBMS but they almost never actually want or need one.