> Consult the classic article on why sophisticated systems like DBMSs do not use mmap: https://db.cs.cmu.edu/mmap-cidr2022/
Sqlite does (or can optionally use mmap). How come?
Is sqlite with mmap less reliable or anything?
Sqlite does (or can optionally use mmap). How come?
Is sqlite with mmap less reliable or anything?
SQLite can use mmap(). That is a tested and supported capability. But we don't advocate it because of the inability to precisely identify I/O errors and report them back up into the application.
https://www.sqlite.org/mmap.html
> The operating system must have a unified buffer cache in order for the memory-mapped I/O extension to work correctly, especially in situations where two processes are accessing the same database file and one process is using memory-mapped I/O while the other is not. Not all operating systems have a unified buffer cache. In some operating systems that claim to have a unified buffer cache, the implementation is buggy and can lead to corrupt databases.
What are those OSes with buggy unified buffer caches? More importantly, is there a list of platforms where the use of mmap in sqlite can lead to data loss?
... it will if two programs open the same sqlite, one with mmap, and another without https://www.sqlite.org/mmap.html - at least "in some operating systems" (no mention of which ones)
https://www.sqlite.org/mmap.html
> The operating system must have a unified buffer cache in order for the memory-mapped I/O extension to work correctly, especially in situations where two processes are accessing the same database file and one process is using memory-mapped I/O while the other is not. Not all operating systems have a unified buffer cache. In some operating systems that claim to have a unified buffer cache, the implementation is buggy and can lead to corrupt databases.
Sqlite is otherwise rock solid and won't lose data as easily