Merge: a face sync that says what it is doing

The face pass announced itself once and then went quiet for the whole export,
upload and adopt. On a first export after a re-index that is eight minutes of a
motionless progress bar, which reads as a hang. It now reports the images it is
preparing, the shards it is sending and their size, and the shards it is taking
in.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

core/dr-catalog/src/face_shard.rs

@@ -531,6 +531,23 @@ pub fn export_to_shards(
     conn: &Connection,
     store: &mut FaceShardStore,
     model_id: &str,
+) -> Result<usize, CatalogError> {
+    export_to_shards_reporting(conn, store, model_id, &mut |_, _| {})
+}
+
+/// [`export_to_shards`], reporting how far it has got.
+///
+/// `progress` is called with `(done, total)` as images are written. The first
+/// export after a re-index is thousands of photographs and the better part of
+/// ten minutes, and a sync that says nothing for that long is indistinguishable
+/// from one that has hung — which is exactly how it was reported. Called every
+/// few dozen images rather than every one, so the channel behind it is not the
+/// expensive part of the loop.
+pub fn export_to_shards_reporting(
+    conn: &Connection,
+    store: &mut FaceShardStore,
+    model_id: &str,
+    progress: &mut dyn FnMut(usize, usize),
 ) -> Result<usize, CatalogError> {
     let mut q = conn.prepare(
         "SELECT r.file_id, fi.image_id, fi.source_edge, fi.indexed_at
@@ -545,8 +562,16 @@ pub fn export_to_shards(
         })?
         .collect::<Result<_, _>>()?;
 
+    /// How often to report. Small enough that a bar moves visibly, large
+    /// enough that the reporting is lost in the write it accompanies.
+    const REPORT_EVERY: usize = 25;
+
+    let total = rows.len();
     let mut exported = 0;
-    for (file_id, image_id, edge, indexed_at) in rows {
+    for (seen, (file_id, image_id, edge, indexed_at)) in rows.into_iter().enumerate() {
+        if seen.is_multiple_of(REPORT_EVERY) {
+            progress(seen, total);
+        }
         // **Not `contains`.** Asking only whether the shard has heard of this
         // image means it is exported once and never again — so re-indexing it
         // updates the catalog and nothing else, and every other device keeps
@@ -593,6 +618,7 @@ pub fn export_to_shards(
         )?;
         exported += 1;
     }
+    progress(total, total);
     Ok(exported)
 }
 

ui/dr-ui/src/derived_sync.rs

@@ -158,7 +158,7 @@ async fn run(
     sync_shards(backend, &base, thumbs_dir, scratch, &mut report).await?;
 
     let _ = tx.send(SyncMessage::Status("checking faces…".into()));
-    sync_face_shards(backend, &base, catalog_path, scratch, &mut report).await?;
+    sync_face_shards(backend, &base, catalog_path, scratch, &mut report, tx).await?;
 
     let _ = tx.send(SyncMessage::Status("checking collections…".into()));
     sync_catalog(backend, &base, catalog_path, scratch, &mut report).await?;
@@ -328,6 +328,7 @@ async fn sync_face_shards(
     catalog_path: &Path,
     scratch: &Path,
     report: &mut SyncReport,
+    tx: &std::sync::mpsc::Sender<SyncMessage>,
 ) -> Result<(), String> {
     use dr_catalog::face_shard::{self, FaceShardStore};
 
@@ -351,7 +352,21 @@ async fn sync_face_shards(
 
     // ---- everything this device has detected, into the shards ------------
     if let Ok(catalog) = dr_catalog::Catalog::open(catalog_path) {
-        match face_shard::export_to_shards(catalog.connection(), &mut store, model) {
+        // The first export after a re-index walks the whole library and writes
+        // thousands of images. Saying so is the difference between a sync that
+        // looks slow and one that looks broken — this pass sat on "checking
+        // faces…" for eight minutes and was reported as a hang.
+        let mut say = |done: usize, total: usize| {
+            let _ = tx.send(SyncMessage::Status(format!(
+                "preparing faces to send: {done}/{total}"
+            )));
+        };
+        match face_shard::export_to_shards_reporting(
+            catalog.connection(),
+            &mut store,
+            model,
+            &mut say,
+        ) {
             Ok(0) => {}
             Ok(n) => log::info!("face sync: {n} newly indexed image(s) ready to upload"),
             Err(e) => log::warn!("face sync: exporting to shards: {e}"),
@@ -377,12 +392,21 @@ async fn sync_face_shards(
 
     // ---- upload ----------------------------------------------------------
     let local = store.shards().map_err(|e| e.to_string())?;
-    for shard in &local {
+    for (n, shard) in local.iter().enumerate() {
         let path = store.shard_path(shard.id);
         let Ok(bytes) = std::fs::read(&path) else {
             continue;
         };
         let name = shard_name(&client, shard.id);
+        // Face shards carry crops and run to tens of megabytes each, so a
+        // single one is a visible wait on any connection. Announced before the
+        // put rather than after, because the wait is the upload.
+        let _ = tx.send(SyncMessage::Status(format!(
+            "sending faces: shard {}/{} ({} MB)",
+            n + 1,
+            local.len(),
+            bytes.len() / 1_048_576
+        )));
 
         // Sealed and present means byte-identical, and the client is in the
         // name so nobody else could have written it. The open shard goes up
@@ -411,6 +435,12 @@ async fn sync_face_shards(
         if owner == client || store.has_adopted(name, *size) {
             continue;
         }
+        // Taking in a peer's shard means a download and then a row-by-row
+        // merge, both of which take a while on a shard carrying crops.
+        let _ = tx.send(SyncMessage::Status(format!(
+            "taking in faces from another device ({} MB)",
+            size / 1_048_576
+        )));
 
         let source = RemotePath::new(format!("{}/{name}", face_base.as_str()));
         let bytes = match backend.get(&RemoteId::Path(source), None).await {