perf(diary): sticker_service 批量 GROUP BY 替代 N+1 贴纸计数 — 8a-C04

- list_sticker_packs: 单次 SQL GROUP BY pack_id 获取所有计数
- 2 次查询（packs + counts）替代 N+1 次
- 使用 PostgreSQL ANY() 传递 UUID 数组
- 测试 80/80 通过

crates/erp-diary/src/service/sticker_service.rs

@@ -1,8 +1,8 @@
 // 贴纸服务 — 贴纸包与贴纸管理
 
 use sea_orm::{
-    ActiveModelTrait, ColumnTrait, DatabaseConnection, EntityTrait, PaginatorTrait,
-    QueryFilter, QueryOrder, Set,
+    ActiveModelTrait, ColumnTrait, ConnectionTrait, DatabaseConnection, EntityTrait,
+    PaginatorTrait, QueryFilter, QueryOrder, Set,
 };
 use uuid::Uuid;
 
@@ -16,7 +16,8 @@ pub struct StickerService;
 impl StickerService {
     /// 获取贴纸包列表
     ///
-    /// 返回所有可用的贴纸包，按分类和名称排序。
+    /// 使用 SQL GROUP BY 批量获取贴纸计数，替代逐包 COUNT 查询。
+    /// 性能: 2 次查询（packs + counts）替代 N+1 次。
     pub async fn list_sticker_packs(
         tenant_id: Uuid,
         category: Option<String>,
@@ -36,24 +37,47 @@ impl StickerService {
             .all(db)
             .await?;
 
-        let mut result = Vec::with_capacity(packs.len());
-        for pack in packs {
-            let sticker_count = sticker::Entity::find()
-                .filter(sticker::Column::PackId.eq(pack.id))
-                .filter(sticker::Column::DeletedAt.is_null())
-                .count(db)
-                .await? as i32;
+        // 批量获取所有贴纸包的贴纸计数 — 单次 SQL GROUP BY（替代 N+1 查询）
+        let pack_ids: Vec<Uuid> = packs.iter().map(|p| p.id).collect();
+        let count_map: std::collections::HashMap<Uuid, i64> = if !pack_ids.is_empty() {
+            let sql = r#"
+                SELECT pack_id, COUNT(*) AS count
+                FROM stickers
+                WHERE pack_id = ANY($1)
+                  AND deleted_at IS NULL
+                GROUP BY pack_id
+            "#;
 
-            result.push(StickerPackResp {
+            let stmt = sea_orm::Statement::from_sql_and_values(
+                sea_orm::DatabaseBackend::Postgres,
+                sql,
+                [pack_ids.into()],
+            );
+
+            let rows = db.query_all(stmt).await?;
+            rows.into_iter()
+                .filter_map(|row| {
+                    let pack_id: Uuid = row.try_get_by_index::<Uuid>(0).ok()?;
+                    let count: i64 = row.try_get_by_index::<i64>(1).ok()?;
+                    Some((pack_id, count))
+                })
+                .collect()
+        } else {
+            std::collections::HashMap::new()
+        };
+
+        let result: Vec<StickerPackResp> = packs
+            .into_iter()
+            .map(|pack| StickerPackResp {
                 id: pack.id,
                 name: pack.name,
                 description: pack.description,
                 cover_image_url: pack.thumbnail_url,
-                sticker_count,
+                sticker_count: *count_map.get(&pack.id).unwrap_or(&0) as i32,
                 is_free: pack.is_free,
                 category: pack.category,
-            });
-        }
+            })
+            .collect();
 
         Ok(result)
     }