Count a Signal's items and unread in one pass (#348)

signal_rows ran the same correlated subquery over signal_verdicts,
entries, subscriptions and entry_state twice a Signal, once for items
and once for unread. One grouped subquery now gives both: count(*) and
a sum of the unread, joined to the person's Signals. Same results on
SQLite and Postgres (the existing counts test runs on both).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ipx/CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Traces show more of where a request's time goes: a page of items' query and its files apart, artwork's cache, check and fetch, the status counts, and each part of changing or leaving a feed (#350).
 - A page of items finds its files by feed as well as item: it read every file's row in the database, about a quarter of a second a page (#344).
 - A page of items asks for its count beside the items, and the feed list asks its five questions at once, where each waited for the one before (#346).
+- A Signal's count of items and of unread ones are worked out in one pass, not two (#348).
 
 ### Fixed
 

crates/ipx/src/db.rs

@@ -2804,23 +2804,25 @@ impl Db {
         let mut a = Args::default();
         let user = a.p(user_id);
         let one = id.map(|i| format!("AND g.id = {}", a.p(i))).unwrap_or_default();
-        // The items it shows, and of those the unread: what its list counts, by the same rules.
+        // The items it shows, and of those the unread: what its list counts, by the same rules. One
-        let hits = |unread: &str| {
+        // pass for both; they were two copies of the same subquery (#348).
-            format!(
+        let sql = format!(
-                "(SELECT count(*) FROM signal_verdicts v
+            "SELECT g.id, g.name, g.keywords, g.description, g.icon,
+                    coalesce(c.items, 0) AS items, coalesce(c.unread, 0) AS unread
+               FROM signals g
+               LEFT JOIN (SELECT v.signal_id, count(*) AS items,
+                                 sum(CASE WHEN NOT coalesce(st.read, false) THEN 1 ELSE 0 END) AS unread
+                            FROM signal_verdicts v
+                            JOIN signals vg ON vg.id = v.signal_id
                             JOIN entries e ON e.feed_id = v.feed_id AND e.guid = v.guid
-                   JOIN subscriptions s ON s.user_id = g.user_id AND s.feed_id = v.feed_id
+                            JOIN subscriptions s ON s.user_id = vg.user_id AND s.feed_id = v.feed_id
-                   LEFT JOIN entry_state st ON st.user_id = g.user_id AND st.feed_id = v.feed_id AND st.guid = v.guid
+                            LEFT JOIN entry_state st
-                  WHERE v.signal_id = g.id AND v.hit AND {unread} AND {} AND {})",
+                                   ON st.user_id = vg.user_id AND st.feed_id = v.feed_id AND st.guid = v.guid
+                           WHERE vg.user_id = {user} AND v.hit AND {} AND {}
+                           GROUP BY v.signal_id) c ON c.signal_id = g.id
+              WHERE g.user_id = {user} {one} ORDER BY lower(g.name), g.id",
             not_hidden(&user),
             shown_in("hide_from_signals", "s")
-            )
-        };
-        let sql = format!(
-            "SELECT g.id, g.name, g.keywords, g.description, g.icon, {} AS items, {} AS unread
-               FROM signals g WHERE g.user_id = {user} {one} ORDER BY lower(g.name), g.id",
-            hits("true"),
-            hits("NOT coalesce(st.read, false)")
         );
         self.rows(&sql, a.0)
             .await?