From 552e886b648faa2a2229d86c7fd9abc8bb5ff99c Mon Sep 17 00:00:00 2001 From: Akihiko Odaki Date: Fri, 28 Aug 2020 16:27:33 +0900 Subject: [PATCH] Eagerly load statuses with the main query in Api::V1::FavouritesController (#14673) The old implementation had two queries: 1. The query constructed in Api::V1::FavouritesController#results 2. The query constructed in #cached_favourites, which is merged with 1. Both of them are issued againt PostgreSQL. The combination of the two queries caused the following problems: - The small window between the two queries involves race conditions. - Minor performance inefficiency. Moreover, the construction of query 2, which involves merging with query 1 has a bug. Query 1 is finalized with paginate_by_id, but paginate_by_id returns an array when min_id parameter is specified. The behavior prevents from merging the query, and in the real world, ActiveRecord simply ignores the merge (!), which results in querying the entire scan of statuses and favourites table. This change fixes these issues by simply letting query 1 get all the works done. --- app/controllers/api/v1/favourites_controller.rb | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/app/controllers/api/v1/favourites_controller.rb b/app/controllers/api/v1/favourites_controller.rb index 3e242905da7..71a707d2a50 100644 --- a/app/controllers/api/v1/favourites_controller.rb +++ b/app/controllers/api/v1/favourites_controller.rb @@ -17,14 +17,11 @@ class Api::V1::FavouritesController < Api::BaseController end def cached_favourites - cache_collection( - Status.reorder(nil).joins(:favourites).merge(results), - Status - ) + cache_collection(results.map(&:status), Status) end def results - @_results ||= account_favourites.paginate_by_id( + @_results ||= account_favourites.eager_load(:status).paginate_by_id( limit_param(DEFAULT_STATUSES_LIMIT), params_slice(:max_id, :since_id, :min_id) )