Optimize federated language updates to avoid unnecessary db writes (#2786)

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

* fix tests

* fix test, rename functions

---------

Co-authored-by: Dessalines <dessalines@users.noreply.github.com>

Cargo.lock

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

crates/api/src/site/leave_admin.rs

@@ -63,7 +63,7 @@ impl Perform for LeaveAdmin {
     let admins = PersonView::admins(context.pool()).await?;
 
     let all_languages = Language::read_all(context.pool()).await?;
-    let discussion_languages = SiteLanguage::read_local(context.pool()).await?;
+    let discussion_languages = SiteLanguage::read_local_raw(context.pool()).await?;
     let taglines = Tagline::get_all(context.pool(), site_view.local_site.id).await?;
     let custom_emojis = CustomEmojiView::get_all(context.pool(), site_view.local_site.id).await?;
 

crates/api_crud/src/community/create.rs

@@ -135,7 +135,7 @@ impl PerformCrud for CreateCommunity {
     // Update the discussion_languages if that's provided
     let community_id = inserted_community.id;
     if let Some(languages) = data.discussion_languages.clone() {
-      let site_languages = SiteLanguage::read_local(context.pool()).await?;
+      let site_languages = SiteLanguage::read_local_raw(context.pool()).await?;
       // check that community languages are a subset of site languages
       // https://stackoverflow.com/a/64227550
       let is_subset = languages.iter().all(|item| site_languages.contains(item));

crates/api_crud/src/community/update.rs

@@ -53,7 +53,7 @@ impl PerformCrud for EditCommunity {
 
     let community_id = data.community_id;
     if let Some(languages) = data.discussion_languages.clone() {
-      let site_languages = SiteLanguage::read_local(context.pool()).await?;
+      let site_languages = SiteLanguage::read_local_raw(context.pool()).await?;
       // check that community languages are a subset of site languages
       // https://stackoverflow.com/a/64227550
       let is_subset = languages.iter().all(|item| site_languages.contains(item));

crates/api_crud/src/site/read.rs

@@ -87,7 +87,7 @@ impl PerformCrud for GetSite {
       build_federated_instances(&site_view.local_site, context.pool()).await?;
 
     let all_languages = Language::read_all(context.pool()).await?;
-    let discussion_languages = SiteLanguage::read_local(context.pool()).await?;
+    let discussion_languages = SiteLanguage::read_local_raw(context.pool()).await?;
     let taglines = Tagline::get_all(context.pool(), site_view.local_site.id).await?;
     let custom_emojis = CustomEmojiView::get_all(context.pool(), site_view.local_site.id).await?;
 

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

@@ -25,7 +25,11 @@ use diesel::{
   ExpressionMethods,
   QueryDsl,
 };
-use diesel_async::{AsyncPgConnection, RunQueryDsl};
+use diesel_async::{
+  pooled_connection::deadpool::Object as PooledConnection,
+  AsyncPgConnection,
+  RunQueryDsl,
+};
 use lemmy_utils::error::LemmyError;
 use tokio::sync::OnceCell;
 
@@ -68,6 +72,13 @@ 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 +90,6 @@ 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,
@@ -98,7 +108,7 @@ impl LocalUserLanguage {
 }
 
 impl SiteLanguage {
-  pub async fn read_local(pool: &DbPool) -> Result<Vec<LanguageId>, Error> {
+  pub async fn read_local_raw(pool: &DbPool) -> Result<Vec<LanguageId>, Error> {
     let conn = &mut get_conn(pool).await?;
     site::table
       .inner_join(local_site::table)
@@ -109,15 +119,22 @@ impl SiteLanguage {
       .await
   }
 
-  pub async fn read(pool: &DbPool, for_site_id: SiteId) -> Result<Vec<LanguageId>, Error> {
-    let conn = &mut get_conn(pool).await?;
-
-    let langs = site_language::table
+  async fn read_raw(
+    conn: &mut PooledConnection<AsyncPgConnection>,
+    for_site_id: SiteId,
+  ) -> Result<Vec<LanguageId>, Error> {
+    site_language::table
       .filter(site_language::site_id.eq(for_site_id))
       .order(site_language::language_id)
       .select(site_language::language_id)
       .load(conn)
-      .await?;
+      .await
+  }
+
+  pub async fn read(pool: &DbPool, for_site_id: SiteId) -> Result<Vec<LanguageId>, Error> {
+    let conn = &mut get_conn(pool).await?;
+    let langs = Self::read_raw(conn, for_site_id).await?;
+
     convert_read_languages(conn, langs).await
   }
 
@@ -129,6 +146,13 @@ 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 +165,6 @@ 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,
@@ -221,19 +244,25 @@ impl CommunityLanguage {
     Ok(())
   }
 
-  pub async fn read(
-    pool: &DbPool,
+  async fn read_raw(
+    conn: &mut PooledConnection<AsyncPgConnection>,
     for_community_id: CommunityId,
   ) -> Result<Vec<LanguageId>, Error> {
     use crate::schema::community_language::dsl::{community_id, community_language, language_id};
-    let conn = &mut get_conn(pool).await?;
-
-    let langs = community_language
+    community_language
       .filter(community_id.eq(for_community_id))
       .order(language_id)
       .select(language_id)
       .get_results(conn)
-      .await?;
+      .await
+  }
+
+  pub async fn read(
+    pool: &DbPool,
+    for_community_id: CommunityId,
+  ) -> Result<Vec<LanguageId>, Error> {
+    let conn = &mut get_conn(pool).await?;
+    let langs = Self::read_raw(conn, for_community_id).await?;
     convert_read_languages(conn, langs).await
   }
 
@@ -243,9 +272,15 @@ 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?;
+      language_ids = SiteLanguage::read_local_raw(pool).await?;
+    }
+    let lang_ids = convert_update_languages(conn, language_ids).await?;
+
+    // No need to update if languages are unchanged
+    let current = CommunityLanguage::read_raw(conn, for_community_id).await?;
+    if current == lang_ids {
+      return Ok(());
     }
 
     conn
@@ -258,7 +293,7 @@ impl CommunityLanguage {
             .execute(conn)
             .await?;
 
-          for l in language_ids {
+          for l in lang_ids {
             let form = CommunityLanguageForm {
               community_id: for_community_id,
               language_id: l,
@@ -464,7 +499,7 @@ mod tests {
     let pool = &build_db_pool_for_tests().await;
 
     let (site, instance) = create_test_site(pool).await;
-    let site_languages1 = SiteLanguage::read_local(pool).await.unwrap();
+    let site_languages1 = SiteLanguage::read_local_raw(pool).await.unwrap();
     // site is created with all languages
     assert_eq!(184, site_languages1.len());
 
@@ -473,7 +508,7 @@ mod tests {
       .await
       .unwrap();
 
-    let site_languages2 = SiteLanguage::read_local(pool).await.unwrap();
+    let site_languages2 = SiteLanguage::read_local_raw(pool).await.unwrap();
     // after update, site only has new languages
     assert_eq!(test_langs, site_languages2);
 
@@ -539,7 +574,7 @@ mod tests {
     assert_eq!(test_langs, read_site_langs);
 
     // Test the local ones are the same
-    let read_local_site_langs = SiteLanguage::read_local(pool).await.unwrap();
+    let read_local_site_langs = SiteLanguage::read_local_raw(pool).await.unwrap();
     assert_eq!(test_langs, read_local_site_langs);
 
     let community_form = CommunityInsertForm::builder()

crates/db_schema/src/impls/community.rs

@@ -2,7 +2,7 @@ use crate::{
   newtypes::{CommunityId, DbUrl, PersonId},
   schema::community::dsl::{actor_id, community, deleted, local, name, removed},
   source::{
-    actor_language::{CommunityLanguage, SiteLanguage},
+    actor_language::CommunityLanguage,
     community::{
       Community,
       CommunityFollower,
@@ -41,6 +41,12 @@ impl Crud for Community {
 
   async fn create(pool: &DbPool, form: &Self::InsertForm) -> Result<Self, Error> {
     let conn = &mut get_conn(pool).await?;
+    let is_new_community = match &form.actor_id {
+      Some(id) => Community::read_from_apub_id(pool, id).await?.is_none(),
+      None => true,
+    };
+
+    // Can't do separate insert/update commands because InsertForm/UpdateForm aren't convertible
     let community_ = insert_into(community)
       .values(form)
       .on_conflict(actor_id)
@@ -49,12 +55,8 @@ 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)
+    // Initialize languages for new community
+    if is_new_community {
       CommunityLanguage::update(pool, vec![], community_.id).await?;
     }
 

crates/db_schema/src/impls/local_user.rs

@@ -83,7 +83,7 @@ impl Crud for LocalUser {
       .await
       .expect("couldnt create local user");
 
-    let site_languages = SiteLanguage::read_local(pool).await;
+    let site_languages = SiteLanguage::read_local_raw(pool).await;
     if let Ok(langs) = site_languages {
       // if site exists, init user with site languages
       LocalUserLanguage::update(pool, langs, local_user_.id).await?;

crates/db_schema/src/impls/site.rs

@@ -25,6 +25,12 @@ impl Crud for Site {
 
   async fn create(pool: &DbPool, form: &Self::InsertForm) -> Result<Self, Error> {
     let conn = &mut get_conn(pool).await?;
+    let is_new_site = match &form.actor_id {
+      Some(id_) => Site::read_from_apub_id(pool, id_).await?.is_none(),
+      None => true,
+    };
+
+    // 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 +39,11 @@ 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 is_new_site {
+      // initialize with all languages
+      SiteLanguage::update(pool, vec![], &site_).await?;
+    }
     Ok(site_)
   }
 
@@ -57,9 +66,8 @@ 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))