fix: delete file lost wake

Signed-off-by: xxchan <[email protected]>

Author: xxchan

crates/iceberg/src/delete_file_index.rs

@@ -16,30 +16,22 @@
 // under the License.
 
 use std::collections::HashMap;
-use std::future::Future;
-use std::ops::Deref;
-use std::pin::Pin;
-use std::sync::{Arc, RwLock};
-use std::task::{Context, Poll};
+use std::sync::{Arc, OnceLock};
 
 use futures::channel::mpsc::{channel, Sender};
 use futures::StreamExt;
+use tokio::sync::Notify;
 
 use crate::runtime::spawn;
 use crate::scan::{DeleteFileContext, FileScanTaskDeleteFile};
 use crate::spec::{DataContentType, DataFile, Struct};
-use crate::{Error, ErrorKind, Result};
+use crate::Result;
 
 /// Index of delete files
 #[derive(Clone, Debug)]
 pub(crate) struct DeleteFileIndex {
-    state: Arc<RwLock<DeleteFileIndexState>>,
-}
-
-#[derive(Debug)]
-enum DeleteFileIndexState {
-    Populating,
-    Populated(PopulatedDeleteFileIndex),
+    index: Arc<OnceLock<PopulatedDeleteFileIndex>>,
+    ready_notify: Arc<Notify>,
 }
 
 #[derive(Debug)]
@@ -59,36 +51,50 @@ impl DeleteFileIndex {
     pub(crate) fn new() -> (DeleteFileIndex, Sender<DeleteFileContext>) {
         // TODO: what should the channel limit be?
         let (tx, rx) = channel(10);
-        let state = Arc::new(RwLock::new(DeleteFileIndexState::Populating));
+        let index = Arc::new(OnceLock::new());
+        let ready_notify = Arc::new(Notify::new());
         let delete_file_stream = rx.boxed();
 
         spawn({
-            let state = state.clone();
+            let index = index.clone();
+            let ready_notify = ready_notify.clone();
             async move {
                 let delete_files = delete_file_stream.collect::<Vec<_>>().await;
 
                 let populated_delete_file_index = PopulatedDeleteFileIndex::new(delete_files);
 
-                let mut guard = state.write().unwrap();
-                *guard = DeleteFileIndexState::Populated(populated_delete_file_index);
+                index
+                    .set(populated_delete_file_index)
+                    .expect("delete file index should not be written by another thread");
+                ready_notify.notify_waiters();
             }
         });
 
-        (DeleteFileIndex { state }, tx)
+        (
+            DeleteFileIndex {
+                index,
+                ready_notify,
+            },
+            tx,
+        )
     }
 
     /// Gets all the delete files that apply to the specified data file.
-    ///
-    /// Returns a future that resolves to a Result<Vec<FileScanTaskDeleteFile>>
-    pub(crate) fn get_deletes_for_data_file<'a>(
+    pub(crate) async fn get_deletes_for_data_file(
         &self,
-        data_file: &'a DataFile,
+        data_file: &DataFile,
         seq_num: Option<i64>,
-    ) -> DeletesForDataFile<'a> {
-        DeletesForDataFile {
-            state: self.state.clone(),
-            data_file,
-            seq_num,
+    ) -> Result<Vec<FileScanTaskDeleteFile>> {
+        match self.index.get() {
+            Some(idx) => Ok(idx.get_deletes_for_data_file(data_file, seq_num)),
+            None => {
+                self.ready_notify.notified().await;
+                Ok(self
+                    .index
+                    .get()
+                    .unwrap()
+                    .get_deletes_for_data_file(data_file, seq_num))
+            }
         }
     }
 }
@@ -193,26 +199,3 @@ impl PopulatedDeleteFileIndex {
         results
     }
 }
-
-/// Future for the `DeleteFileIndex::get_deletes_for_data_file` method
-pub(crate) struct DeletesForDataFile<'a> {
-    state: Arc<RwLock<DeleteFileIndexState>>,
-    data_file: &'a DataFile,
-    seq_num: Option<i64>,
-}
-
-impl Future for DeletesForDataFile<'_> {
-    type Output = Result<Vec<FileScanTaskDeleteFile>>;
-
-    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
-        match self.state.try_read() {
-            Ok(guard) => match guard.deref() {
-                DeleteFileIndexState::Populated(idx) => Poll::Ready(Ok(
-                    idx.get_deletes_for_data_file(self.data_file, self.seq_num)
-                )),
-                _ => Poll::Pending,
-            },
-            Err(err) => Poll::Ready(Err(Error::new(ErrorKind::Unexpected, err.to_string()))),
-        }
-    }
-}