pub fn create_with_wal(id: usize, path: impl AsRef<Path>) -> Result<Self> {
        Ok(Self {
            id,
            map: Arc::new(SkipMap::new()),
            wal: Some(Wal::create(path.as_ref())?),
            approximate_size: Arc::new(AtomicUsize::new(0)),
        })
    }
Create a new mem-table with WAL
mini-lsm/src/mem_table.rs