models/download: Add a slim Version model to reduce data loading

src/controllers/krate/downloads.rs

@@ -5,7 +5,8 @@
 
 use crate::app::AppState;
 use crate::controllers::krate::CratePath;
-use crate::models::{Version, VersionDownload};
+use crate::models::download::Version;
+use crate::models::VersionDownload;
 use crate::schema::{version_downloads, versions};
 use crate::util::errors::AppResult;
 use crate::views::EncodableVersionDownload;
@@ -42,7 +43,7 @@ pub async fn get_crate_downloads(state: AppState, path: CratePath) -> AppResult<
         .load(&mut conn)
         .await?;
 
-    versions.sort_by_cached_key(|version| cmp::Reverse(semver::Version::parse(&version.num).ok()));
+    versions.sort_unstable_by(|a, b| b.num.cmp(&a.num));
     let (latest_five, rest) = versions.split_at(cmp::min(5, versions.len()));
 
     let downloads = VersionDownload::belonging_to(latest_five)

src/models.rs

@@ -26,7 +26,7 @@ pub mod crate_owner_invitation;
 pub mod default_versions;
 mod deleted_crate;
 pub mod dependency;
-mod download;
+pub mod download;
 mod email;
 mod follow;
 mod keyword;

src/models/download.rs

@@ -1,13 +1,31 @@
-use crate::models::Version;
-use crate::schema::version_downloads;
+use crate::models::Version as FullVersion;
+use crate::schema::{version_downloads, versions};
 use chrono::NaiveDate;
+use crates_io_diesel_helpers::SemverVersion;
 
 #[derive(Queryable, Identifiable, Associations, Debug, Clone, Copy)]
-#[diesel(primary_key(version_id, date), belongs_to(Version))]
+#[diesel(
+    primary_key(version_id, date),
+    belongs_to(FullVersion, foreign_key=version_id),
+    belongs_to(Version),
+)]
 pub struct VersionDownload {
     pub version_id: i32,
     pub downloads: i32,
     pub counted: i32,
     pub date: NaiveDate,
     pub processed: bool,
 }
+
+/// A subset of the columns of the `versions` table.
+///
+/// This struct is used to load all versions of a crate from the database,
+/// without loading the additional data that is unnecessary for download version resolution.
+///
+#[derive(Queryable, Selectable, Identifiable)]
+#[diesel(table_name = versions)]
+pub struct Version {
+    pub id: i32,
+    #[diesel(deserialize_as = SemverVersion)]
+    pub num: semver::Version,
+}