controllers/category: Pipeline SQL queries

crates/crates_io_database/src/models/category.rs

@@ -5,6 +5,8 @@ use diesel::dsl;
 use diesel::prelude::*;
 use diesel_async::scoped_futures::ScopedFutureExt;
 use diesel_async::{AsyncConnection, AsyncPgConnection, RunQueryDsl};
+use futures_util::future::BoxFuture;
+use futures_util::FutureExt;
 use std::future::Future;
 
 #[derive(Clone, Identifiable, Queryable, QueryableByName, Debug, Selectable)]
@@ -116,13 +118,16 @@ impl Category {
             .load(conn)
     }
 
-    pub async fn subcategories(&self, conn: &mut AsyncPgConnection) -> QueryResult<Vec<Category>> {
+    pub fn subcategories(
+        &self,
+        conn: &mut AsyncPgConnection,
+    ) -> BoxFuture<'_, QueryResult<Vec<Category>>> {
         use diesel::sql_types::Text;
 
         diesel::sql_query(include_str!("subcategories.sql"))
             .bind::<Text, _>(&self.category)
             .load(conn)
-            .await
+            .boxed()
     }
 
     /// Gathers the parent categories from the top-level Category to the direct parent of this Category.

src/controllers/category.rs

@@ -8,6 +8,7 @@ use axum::Json;
 use axum::extract::{FromRequestParts, Path, Query};
 use diesel::QueryDsl;
 use diesel_async::RunQueryDsl;
+use futures_util::FutureExt;
 use http::request::Parts;
 
 #[derive(Debug, Deserialize, FromRequestParts, utoipa::IntoParams)]
@@ -62,11 +63,13 @@ pub async fn list_categories(
 
     let offset = options.offset().unwrap_or_default();
 
-    let categories = Category::toplevel(&mut conn, sort, options.per_page, offset).await?;
-    let categories = categories.into_iter().map(Category::into).collect();
+    let (categories, total) = tokio::try_join!(
+        Category::toplevel(&mut conn, sort, options.per_page, offset).boxed(),
+        // Query for the total count of categories
+        Category::count_toplevel(&mut conn).boxed(),
+    )?;
 
-    // Query for the total count of categories
-    let total = Category::count_toplevel(&mut conn).await?;
+    let categories = categories.into_iter().map(Category::into).collect();
 
     let meta = ListMeta { total };
     Ok(Json(ListResponse { categories, meta }))
@@ -94,18 +97,13 @@ pub async fn find_category(
     let mut conn = state.db_read().await?;
 
     let cat: Category = Category::by_slug(&slug).first(&mut conn).await?;
-    let subcats = cat
-        .subcategories(&mut conn)
-        .await?
-        .into_iter()
-        .map(Category::into)
-        .collect();
-    let parents = cat
-        .parent_categories(&mut conn)
-        .await?
-        .into_iter()
-        .map(Category::into)
-        .collect();
+    let (subcats, parents) = tokio::try_join!(
+        cat.subcategories(&mut conn),
+        cat.parent_categories(&mut conn).boxed(),
+    )?;
+
+    let subcats = subcats.into_iter().map(Category::into).collect();
+    let parents = parents.into_iter().map(Category::into).collect();
 
     let mut category = EncodableCategory::from(cat);
     category.subcategories = Some(subcats);