add setting for checkpoint period

src/db.rs

@@ -27,11 +27,32 @@ pub struct Db {
     background_thread: JoinHandle<()>,
 }
 
-#[derive(Default)]
-pub struct Setting {}
+pub struct Setting {
+    pub checkpoint_period: Duration,
+}
+
+impl std::default::Default for Setting {
+    fn default() -> Self {
+        Self {
+            checkpoint_period: Duration::from_secs(60 * 60),
+        }
+    }
+}
+
+impl Setting {
+    fn validate(&self) -> anyhow::Result<()> {
+        if self.checkpoint_period.as_secs() < 5 {
+            return Err(anyhow!("checkpoint period can't be less than 5 seconds"));
+        }
+
+        Ok(())
+    }
+}
 
 impl Db {
-    pub fn open(path: &Path, _setting: Setting) -> anyhow::Result<Self> {
+    pub fn open(path: &Path, setting: Setting) -> anyhow::Result<Self> {
+        setting.validate()?;
+
         if !path.exists() {
             std::fs::create_dir_all(path)?;
         }
@@ -90,7 +111,7 @@ impl Db {
             let pager = pager.clone();
             let tx_state = tx_state.clone();
             std::thread::spawn(move || loop {
-                let Err(err) = receiver.recv_timeout(Duration::from_secs(60 * 60)) else {
+                let Err(err) = receiver.recv_timeout(setting.checkpoint_period) else {
                     break;
                 };
                 if err != std::sync::mpsc::RecvTimeoutError::Timeout {
@@ -229,6 +250,12 @@ impl Db {
             return Err(anyhow!("cannot join background thread"));
         }
 
+        // Since we own self, it means there are no active transaction since active transaction
+        // borrows the db. And there are no ongoing flush and checkpoint since they also borrow
+        // the db. The background thread to periodically flush and perform checkpoint is also
+        // finished due to the join above.
+        Self::checkpoint(&self.pager, &self.wal, &self.tx_state)?;
+
         // Since the background thread is finished, it means it doesn't hold the WAL anymore and
         // we can take the wal from Arc
         let wal = Arc::into_inner(self.wal).unwrap();