add db::Writer::load

src/db.rs

@@ -79,6 +79,7 @@ where
             _t: PhantomData,
         })
     }
+
     pub fn push(&mut self, item: T) -> Result<(), String> {
         let pos: LSize = self.data_buf.position() as LSize;
 
@@ -102,6 +103,18 @@ where
 
         Ok(())
     }
+
+    pub fn load<I>(&mut self, iter: &mut I) -> Result<(), String>
+    where
+        I: Iterator<Item = T>,
+    {
+        for item in iter {
+            self.push(item)?;
+        }
+
+        Ok(())
+    }
+
     pub fn finish(mut self) -> Result<(), String> {
         // finish tab
         let pos: LSize = self.data_buf.position() as LSize;

src/main.rs

@@ -269,16 +269,16 @@ fn db_writer2_task(rx: mpsc::Receiver<Question>) {
         db::Writer::new(NEW_DB_FILENAME, writer_opts).expect("new db writer");
 
     let mut num = 1;
-    rx.into_iter().for_each(|mut q| {
+    let mut iter = rx.iter().map(|mut q| {
         q.num = num;
-
-        writer
-            .push(q)
-            .unwrap_or_else(|e| panic!("db writer push, num={num}, {e:#?}"));
-
         num += 1;
+        q
     });
 
+    writer
+        .load(&mut iter)
+        .unwrap_or_else(|e| panic!("db writer push, num={num}, {e:#?}"));
+
     writer.finish().expect("db writer finish");
 
     println!("write done");