Optimize federated language updates to avoid unnecessary db writes (fixes #2772)

Cargo.lock

@@ -2517,6 +2517,7 @@ dependencies = [
  "diesel-derive-newtype",
  "diesel_ltree",
  "diesel_migrations",
+ "futures",
  "lemmy_utils",
  "once_cell",
  "regex",

crates/apub/src/api/read_community.rs

@@ -80,7 +80,7 @@ impl PerformApub for GetCommunity {
 
     let site_id =
       Site::instance_actor_id_from_url(community_view.community.actor_id.clone().into());
-    let mut site = Site::read_from_apub_id(context.pool(), site_id).await?;
+    let mut site = Site::read_from_apub_id(context.pool(), &site_id.into()).await?;
     // no need to include metadata for local site (its already available through other endpoints).
     // this also prevents us from leaking the federation private key.
     if let Some(s) = &site {

crates/apub/src/objects/instance.rs

@@ -71,7 +71,7 @@ impl Object for ApubSite {
     data: &Data<Self::DataType>,
   ) -> Result<Option<Self>, LemmyError> {
     Ok(
-      Site::read_from_apub_id(data.pool(), object_id)
+      Site::read_from_apub_id(data.pool(), &object_id.into())
         .await?
         .map(Into::into),
     )

crates/db_schema/Cargo.toml

@@ -41,6 +41,7 @@ async-trait = { workspace = true }
 tokio = { workspace = true }
 tracing = { workspace = true }
 tracing-error = { workspace = true }
+futures = { workspace = true }
 deadpool = { version = "0.9.5", features = ["rt_tokio_1"], optional = true }
 
 [dev-dependencies]

crates/db_schema/src/impls/actor_language.rs

@@ -68,6 +68,13 @@ impl LocalUserLanguage {
     for_local_user_id: LocalUserId,
   ) -> Result<(), Error> {
     let conn = &mut get_conn(pool).await?;
+    let lang_ids = convert_update_languages(conn, language_ids).await?;
+
+    // No need to update if languages are unchanged
+    let current = LocalUserLanguage::read(pool, for_local_user_id).await?;
+    if current == lang_ids {
+      return Ok(());
+    }
 
     conn
       .build_transaction()
@@ -79,7 +86,6 @@ impl LocalUserLanguage {
             .execute(conn)
             .await?;
 
-          let lang_ids = convert_update_languages(conn, language_ids).await?;
           for l in lang_ids {
             let form = LocalUserLanguageForm {
               local_user_id: for_local_user_id,
@@ -129,6 +135,13 @@ impl SiteLanguage {
     let conn = &mut get_conn(pool).await?;
     let for_site_id = site.id;
     let instance_id = site.instance_id;
+    let lang_ids = convert_update_languages(conn, language_ids).await?;
+
+    // No need to update if languages are unchanged
+    let current = SiteLanguage::read(pool, site.id).await?;
+    if current == lang_ids {
+      return Ok(());
+    }
 
     conn
       .build_transaction()
@@ -141,7 +154,6 @@ impl SiteLanguage {
             .execute(conn)
             .await?;
 
-          let lang_ids = convert_update_languages(conn, language_ids).await?;
           for l in lang_ids {
             let form = SiteLanguageForm {
               site_id: for_site_id,
@@ -243,11 +255,16 @@ impl CommunityLanguage {
     for_community_id: CommunityId,
   ) -> Result<(), Error> {
     let conn = &mut get_conn(pool).await?;
-
     if language_ids.is_empty() {
       language_ids = SiteLanguage::read_local(pool).await?;
     }
 
+    // No need to update if languages are unchanged
+    let current = CommunityLanguage::read(pool, for_community_id).await?;
+    if current == language_ids {
+      return Ok(());
+    }
+
     conn
       .build_transaction()
       .run(|conn| {

crates/db_schema/src/impls/community.rs

@@ -21,6 +21,7 @@ use crate::{
 };
 use diesel::{dsl::insert_into, result::Error, ExpressionMethods, QueryDsl, TextExpressionMethods};
 use diesel_async::RunQueryDsl;
+use futures::future::OptionFuture;
 
 #[async_trait]
 impl Crud for Community {
@@ -41,6 +42,14 @@ impl Crud for Community {
 
   async fn create(pool: &DbPool, form: &Self::InsertForm) -> Result<Self, Error> {
     let conn = &mut get_conn(pool).await?;
+    let existing = OptionFuture::from(
+      form
+        .actor_id
+        .as_ref()
+        .map(|id| Community::read_from_apub_id(pool, id)),
+    )
+    .await;
+    // Can't do separate insert/update commands because InsertForm/UpdateForm aren't convertible
     let community_ = insert_into(community)
       .values(form)
       .on_conflict(actor_id)
@@ -49,13 +58,16 @@ impl Crud for Community {
       .get_result::<Self>(conn)
       .await?;
 
-    let site_languages = SiteLanguage::read_local(pool).await;
-    if let Ok(langs) = site_languages {
-      // if site exists, init user with site languages
-      CommunityLanguage::update(pool, langs, community_.id).await?;
-    } else {
-      // otherwise, init with all languages (this only happens during tests)
-      CommunityLanguage::update(pool, vec![], community_.id).await?;
+    // Initialize languages for new community
+    if existing.is_none() {
+      let site_languages = SiteLanguage::read_local(pool).await;
+      if let Ok(langs) = site_languages {
+        // if site exists, init community with site languages
+        CommunityLanguage::update(pool, langs, community_.id).await?;
+      } else {
+        // otherwise, init with all languages (this only happens during tests)
+        CommunityLanguage::update(pool, vec![], community_.id).await?;
+      }
     }
 
     Ok(community_)

crates/db_schema/src/impls/site.rs

@@ -10,6 +10,7 @@ use crate::{
 };
 use diesel::{dsl::insert_into, result::Error, ExpressionMethods, QueryDsl};
 use diesel_async::RunQueryDsl;
+use futures::future::OptionFuture;
 use url::Url;
 
 #[async_trait]
@@ -25,6 +26,14 @@ impl Crud for Site {
 
   async fn create(pool: &DbPool, form: &Self::InsertForm) -> Result<Self, Error> {
     let conn = &mut get_conn(pool).await?;
+    let existing = OptionFuture::from(
+      form
+        .actor_id
+        .as_ref()
+        .map(|id_| Site::read_from_apub_id(pool, id_)),
+    )
+    .await;
+    // Can't do separate insert/update commands because InsertForm/UpdateForm aren't convertible
     let site_ = insert_into(site)
       .values(form)
       .on_conflict(actor_id)
@@ -33,8 +42,11 @@ impl Crud for Site {
       .get_result::<Self>(conn)
       .await?;
 
-    // initialize with all languages
-    SiteLanguage::update(pool, vec![], &site_).await?;
+    // initialize languages if site is newly created
+    if existing.is_none() {
+      // initialize with all languages
+      SiteLanguage::update(pool, vec![], &site_).await?;
+    }
     Ok(site_)
   }
 
@@ -57,9 +69,8 @@ impl Crud for Site {
 }
 
 impl Site {
-  pub async fn read_from_apub_id(pool: &DbPool, object_id: Url) -> Result<Option<Self>, Error> {
+  pub async fn read_from_apub_id(pool: &DbPool, object_id: &DbUrl) -> Result<Option<Self>, Error> {
     let conn = &mut get_conn(pool).await?;
-    let object_id: DbUrl = object_id.into();
     Ok(
       site
         .filter(actor_id.eq(object_id))