On: But how, exactly, do databases use mmap?

[vlovich123]

Does that generalize to databases? My understanding is that file systems are a restricted case of databases that don’t necessarily support all operations (eg transactions are smaller, can’t do arbitrary queries within a transaction, etc etc).

[jorangreef → vlovich123]

I think it would, because if your underlying file system can provide crash consistency then that can be leveraged as a primitive by the database.