Filter the people rail in the query, and count the unassigned faces

`faces::people` grouped `face_person` after a LEFT JOIN over every person
and sorted the lot by name; the rail then discarded the empty, unnamed
groups a regrouping pass leaves behind — 17,000 of 19,000 rows on the
reference library. `people_in_use` filters them in the WHERE and joins
`people` to face counts aggregated first (2,000 groups), so the sort sees
only the rows that will be drawn. `count_unassigned` replaces fetching
2,400 ids to take their length. `load_people` 22 ms → 10 ms.

core/dr-catalog/src/faces.rs

@@ -838,6 +838,22 @@ pub fn unassigned(conn: &Connection, model_id: &str) -> Result<Vec<FaceId>, Cata
     rows.collect::<Result<_, _>>().map_err(Into::into)
 }
 
+/// How many faces have no identity yet — [`unassigned`] counted rather than
+/// listed, for a screen that only shows the number.
+pub fn count_unassigned(conn: &Connection, model_id: &str) -> Result<u64, CatalogError> {
+    let n: i64 = conn.query_row(
+        &format!(
+            "SELECT COUNT(*) FROM faces f
+              LEFT JOIN face_person fp ON fp.face_id = f.id
+              WHERE fp.face_id IS NULL AND {} = ?1",
+            embedder_sql("f.model_id")
+        ),
+        [embedder_of(model_id)],
+        |r| r.get(0),
+    )?;
+    Ok(n as u64)
+}
+
 /// One face's stored embedding, as the clustering pass consumes it.
 ///
 /// A struct rather than a tuple because it crosses a crate boundary and "the
@@ -910,17 +926,46 @@ pub fn rename_person(conn: &Connection, person: PersonId, name: &str) -> Result<
 /// Merged-away people are excluded: they exist as redirects so a sync does not
 /// resurrect them, not as entries in a list.
 pub fn people(conn: &Connection) -> Result<Vec<Person>, CatalogError> {
-    let mut q = conn.prepare(
+    people_where(conn, false)
+}
+
+/// Everyone who holds a face, carries a name, or was set aside — the people a
+/// screen has a row for.
+///
+/// The rest are the empty, unnamed groups a regrouping pass leaves behind
+/// (`prune_empty_unnamed`), and on the reference library they were 17,000 of
+/// 19,000 rows: read, counted, sorted by name and then thrown away by the
+/// caller on every redraw. Filtered here, in the query, they are never
+/// sorted. The filter is SQL's `trim`, which strips spaces and not every
+/// whitespace character, so a name that is only a tab is listed rather than
+/// hidden — the safe direction for a row the user typed something into.
+pub fn people_in_use(conn: &Connection) -> Result<Vec<Person>, CatalogError> {
+    people_where(conn, true)
+}
+
+/// [`people`], with face counts aggregated once per person *before* the join
+/// rather than grouped after it: the face table is joined to the 2,000
+/// people it names, not the 19,000 rows of the people table.
+fn people_where(conn: &Connection, in_use: bool) -> Result<Vec<Person>, CatalogError> {
+    let filter = if in_use {
+        "AND (c.person_id IS NOT NULL OR trim(p.name) <> '' OR p.ignored)"
+    } else {
+        ""
+    };
+    let mut q = conn.prepare(&format!(
         "SELECT p.id, p.uuid, p.name,
-                COALESCE(SUM(fp.confirmed = 1), 0),
-                COALESCE(SUM(fp.confirmed = 0), 0),
+                COALESCE(c.confirmed, 0),
+                COALESCE(c.suggested, 0),
                 p.ignored
            FROM people p
-           LEFT JOIN face_person fp ON fp.person_id = p.id
-          WHERE p.merged_into IS NULL
-          GROUP BY p.id
-          ORDER BY 4 DESC, 5 DESC, p.name",
-    )?;
+           LEFT JOIN (SELECT person_id,
+                             SUM(confirmed = 1) AS confirmed,
+                             SUM(confirmed = 0) AS suggested
+                        FROM face_person
+                       GROUP BY person_id) c ON c.person_id = p.id
+          WHERE p.merged_into IS NULL {filter}
+          ORDER BY 4 DESC, 5 DESC, p.name"
+    ))?;
     let rows = q.query_map([], |r| {
         Ok(Person {
             id: PersonId(r.get::<_, i64>(0)? as u64),

ui/dr-ui/src/identity.rs

@@ -216,7 +216,9 @@ pub struct IdentityView {
 /// Filtered rather than deleted, because this is a screen being drawn and not a
 /// catalog being repaired. A row is withheld; nothing is lost, a sync cannot
 /// resurrect what was never removed, and the prune stays the one place that
-/// decides these are disposable.
+/// decides these are disposable. The filter is the catalog's
+/// (`faces::people_in_use`), in the query, so the rows withheld are never
+/// read or sorted either.
 ///
 /// An empty group with a *name* still shows. That one is not debris, it is the
 /// symptom of a real failure — a named person whose faces were regrouped out
@@ -228,11 +230,8 @@ pub fn load_people(
     model_id: &str,
 ) -> Result<IdentityView, dr_catalog::CatalogError> {
     let conn = catalog.connection();
-    let people = faces::people(conn)?
+    let people = faces::people_in_use(conn)?
         .into_iter()
-        .filter(|p| {
-            p.confirmed_faces + p.suggested_faces > 0 || !p.name.trim().is_empty() || p.ignored
-        })
         .map(|p| PersonRow {
             id: p.id,
             name: p.name,
@@ -247,7 +246,7 @@ pub fn load_people(
         people,
         selected: None,
         faces: Vec::new(),
-        unassigned: faces::unassigned(conn, model_id)?.len(),
+        unassigned: faces::count_unassigned(conn, model_id)? as usize,
         calibrated: faces::calibration(conn, model_id)?.is_some_and(|(c, _)| c.valid),
     })
 }