[wmanley]

SQLite in mmap mode (not the default) will use mmap for reading. It will still use write using `pwrite` so it can detect and recover from write failures.

See https://www.sqlite.org/mmap.html :

> The default mechanism by which SQLite accesses and updates database disk files is the xRead() and xWrite() methods of the sqlite3_io_methods VFS object. These methods are typically implemented as "read()" and "write()" system calls which cause the operating system to copy disk content between the kernel buffer cache and user space.

> Beginning with version 3.7.17 (2013-05-20), SQLite has the option of accessing disk content directly using memory-mapped I/O and the new xFetch() and xUnfetch() methods on sqlite3_io_methods.

The principal advantage to mmap in my mind is that the cache is shared among your SQLite connections.