fix: correct keyset pagination cursor and stable totalCount

The cursor condition used only `id > after_id` but ORDER BY was
`(full_name, id)` / `(name, id)`, causing duplicates and skipped items
across pages when row IDs didn't match alphabetical sort order.

Additionally, COUNT(*) OVER() included the cursor condition, making
totalCount shrink on page 2+.

Fix: use a proper composite keyset condition
`(sort_col > $val OR (sort_col = $val AND id > $id))` and wrap the
base query in a MATERIALIZED CTE when a cursor is present so the
window-function count reflects all filtered rows.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: graylikeme

crates/api/src/db/equipment.rs

@@ -35,7 +35,7 @@ pub async fn search(
     pool: &PgPool,
     filter: EquipmentFilter<'_>,
     first: i64,
-    after_id: Option<i32>,
+    after_cursor: Option<(&str, i32)>,
 ) -> Result<(Vec<DbEquipment>, i64, bool), AppError> {
     // Pre-resolve ammo_for_slug to ID
     let resolved_ammo_for_id = if let Some(slug) = filter.ammo_for_slug {
@@ -47,7 +47,15 @@ pub async fn search(
         None
     };
 
-    let mut builder = sqlx::QueryBuilder::<sqlx::Postgres>::new(
+    let has_cursor = after_cursor.is_some();
+
+    let mut builder = sqlx::QueryBuilder::<sqlx::Postgres>::new("");
+
+    if has_cursor {
+        builder.push("WITH filtered AS MATERIALIZED (");
+    }
+
+    builder.push(
         r#"SELECT id, slug, name, category::text AS category, tech_base::text AS tech_base,
                   rules_level::text AS rules_level, tonnage, crits, damage, heat,
                   range_min, range_short, range_medium, range_long, bv, intro_year,
@@ -91,9 +99,15 @@ pub async fn search(
         builder.push(" AND ammo_for_id = ");
         builder.push_bind(weapon_id);
     }
-    if let Some(aid) = after_id {
+
+    if let Some((sort_val, after_id)) = after_cursor {
+        builder.push(") SELECT * FROM filtered WHERE (name > ");
+        builder.push_bind(sort_val);
+        builder.push(" OR (name = ");
+        builder.push_bind(sort_val);
         builder.push(" AND id > ");
-        builder.push_bind(aid);
+        builder.push_bind(after_id);
+        builder.push("))");
     }
 
     builder.push(" ORDER BY name, id LIMIT ");

crates/api/src/db/units.rs

@@ -59,14 +59,24 @@ pub async fn search(
     pool: &PgPool,
     filter: UnitFilter<'_>,
     first: i64,
-    after_id: Option<i32>,
+    after_cursor: Option<(&str, i32)>,
 ) -> Result<(Vec<DbUnit>, i64, bool), AppError> {
     let has_mech_filter = filter.is_omnimech.is_some()
         || filter.config.is_some()
         || filter.engine_type.is_some()
         || filter.has_jump.is_some();
+    let has_cursor = after_cursor.is_some();
 
-    let mut builder = sqlx::QueryBuilder::<sqlx::Postgres>::new(
+    let mut builder = sqlx::QueryBuilder::<sqlx::Postgres>::new("");
+
+    // When paginating with a cursor, wrap the base query in a MATERIALIZED CTE
+    // so that COUNT(*) OVER() reflects the total filtered rows (not just rows
+    // after the cursor position).
+    if has_cursor {
+        builder.push("WITH filtered AS MATERIALIZED (");
+    }
+
+    builder.push(
         r#"SELECT u.id, u.slug, u.chassis_id, u.variant, u.full_name,
                   u.tech_base::text AS tech_base, u.rules_level::text AS rules_level,
                   u.tonnage, u.bv, u.cost, u.intro_year, u.extinction_year,
@@ -144,12 +154,20 @@ pub async fn search(
         builder.push(" AND u.role = ");
         builder.push_bind(role);
     }
-    if let Some(aid) = after_id {
-        builder.push(" AND u.id > ");
-        builder.push_bind(aid);
+
+    // Close CTE and apply keyset cursor condition in the outer query.
+    // The cursor uses (full_name, id) to match the ORDER BY columns.
+    if let Some((sort_val, after_id)) = after_cursor {
+        builder.push(") SELECT * FROM filtered WHERE (full_name > ");
+        builder.push_bind(sort_val);
+        builder.push(" OR (full_name = ");
+        builder.push_bind(sort_val);
+        builder.push(" AND id > ");
+        builder.push_bind(after_id);
+        builder.push("))");
     }
 
-    builder.push(" ORDER BY u.full_name, u.id LIMIT ");
+    builder.push(" ORDER BY full_name, id LIMIT ");
     builder.push_bind(first + 1);
 
     let mut rows = builder

crates/api/src/graphql/query.rs

@@ -154,10 +154,7 @@ impl QueryRoot {
     ) -> Result<UnitConnection, AppError> {
         let state = ctx.data::<AppState>().unwrap();
         let first = first.unwrap_or(20).clamp(1, 100) as i64;
-        let after_id = after
-            .as_deref()
-            .and_then(decode_cursor)
-            .map(|(_, id)| id);
+        let after_cursor = after.as_deref().and_then(decode_cursor);
 
         let filter = units::UnitFilter {
             name_search: name_search.as_deref(),
@@ -174,8 +171,13 @@ impl QueryRoot {
             role: role.as_deref(),
         };
 
-        let (rows, total_count, has_next) =
-            units::search(&state.pool, filter, first, after_id).await?;
+        let (rows, total_count, has_next) = units::search(
+            &state.pool,
+            filter,
+            first,
+            after_cursor.as_ref().map(|(s, id)| (s.as_str(), *id)),
+        )
+        .await?;
 
         let edges: Vec<UnitEdge> = rows
             .into_iter()
@@ -195,7 +197,7 @@ impl QueryRoot {
             edges,
             page_info: PageInfo {
                 has_next_page: has_next,
-                has_previous_page: after_id.is_some(),
+                has_previous_page: after_cursor.is_some(),
                 start_cursor,
                 end_cursor,
                 total_count,
@@ -259,10 +261,7 @@ impl QueryRoot {
     ) -> Result<EquipmentConnection, AppError> {
         let state = ctx.data::<AppState>().unwrap();
         let first = first.unwrap_or(20).clamp(1, 100) as i64;
-        let after_id = after
-            .as_deref()
-            .and_then(decode_cursor)
-            .map(|(_, id)| id);
+        let after_cursor = after.as_deref().and_then(decode_cursor);
 
         let filter = equipment::EquipmentFilter {
             name_search: name_search.as_deref(),
@@ -279,7 +278,7 @@ impl QueryRoot {
             &state.pool,
             filter,
             first,
-            after_id,
+            after_cursor.as_ref().map(|(s, id)| (s.as_str(), *id)),
         )
         .await?;
 
@@ -301,7 +300,7 @@ impl QueryRoot {
             edges,
             page_info: PageInfo {
                 has_next_page: has_next,
-                has_previous_page: after_id.is_some(),
+                has_previous_page: after_cursor.is_some(),
                 start_cursor,
                 end_cursor,
                 total_count,