Fix PostgreSQL load when linking in announcements (#13250)

* Fix PostgreSQL load when linking in announcements

Fixes #13245 by caching status lookups

Since statuses are supposed to be known already and we only
need their URLs and a few other things, caching them should
be fine.

Since it's only used by announcements so far, there won't
be much statuses to cache.

* Perform status lookup when saving announcements, not when rendering them

* Change EntityCache#status to fetch URLs instead of looking into the database

* Move announcement link lookup to publishing worker

* Address issues pointed out during review

6 files changed, 32 insertions, 5 deletions

diff --git a/app/lib/entity_cache.rb b/app/lib/entity_cache.rb
index 35a3773d2..afdbd70f2 100644
--- a/app/lib/entity_cache.rb
+++ b/app/lib/entity_cache.rb
@@ -7,6 +7,10 @@ class EntityCache
 
   MAX_EXPIRATION = 7.days.freeze
 
+  def status(url)
+    Rails.cache.fetch(to_key(:status, url), expires_in: MAX_EXPIRATION) { FetchRemoteStatusService.new.call(url) }
+  end
+
   def mention(username, domain)
     Rails.cache.fetch(to_key(:mention, username, domain), expires_in: MAX_EXPIRATION) { Account.select(:id, :username, :domain, :url).find_remote(username, domain) }
   end
diff --git a/app/models/announcement.rb b/app/models/announcement.rb
index f8ac4e09d..a4e427b49 100644
--- a/app/models/announcement.rb
+++ b/app/models/announcement.rb
@@ -14,6 +14,7 @@
 #  created_at   :datetime         not null
 #  updated_at   :datetime         not null
 #  published_at :datetime
+#  status_ids   :bigint           is an Array
 #
 
 class Announcement < ApplicationRecord
@@ -49,7 +50,13 @@ class Announcement < ApplicationRecord
   end
 
   def statuses
-    @statuses ||= Status.from_text(text)
+    @statuses ||= begin
+      if status_ids.nil?
+        []
+      else
+        Status.where(id: status_ids, visibility: [:public, :unlisted])
+      end
+    end
   end
 
   def tags
diff --git a/app/models/status.rb b/app/models/status.rb
index ff653100a..fef4e2596 100644
--- a/app/models/status.rb
+++ b/app/models/status.rb
@@ -379,7 +379,7 @@ class Status < ApplicationRecord
           if TagManager.instance.local_url?(url)
             ActivityPub::TagManager.instance.uri_to_resource(url, Status)
           else
-            Status.find_by(uri: url) || Status.find_by(url: url)
+            EntityCache.instance.status(url)
           end
         end
         status&.distributable? ? status : nil
diff --git a/app/workers/publish_scheduled_announcement_worker.rb b/app/workers/publish_scheduled_announcement_worker.rb
index efca39d3d..1392efed0 100644
--- a/app/workers/publish_scheduled_announcement_worker.rb
+++ b/app/workers/publish_scheduled_announcement_worker.rb
@@ -5,15 +5,24 @@ class PublishScheduledAnnouncementWorker
   include Redisable
 
   def perform(announcement_id)
-    announcement = Announcement.find(announcement_id)
+    @announcement = Announcement.find(announcement_id)
 
-    announcement.publish! unless announcement.published?
+    refresh_status_ids!
 
-    payload = InlineRenderer.render(announcement, nil, :announcement)
+    @announcement.publish! unless @announcement.published?
+
+    payload = InlineRenderer.render(@announcement, nil, :announcement)
     payload = Oj.dump(event: :announcement, payload: payload)
 
     FeedManager.instance.with_active_accounts do |account|
       redis.publish("timeline:#{account.id}", payload) if redis.exists("subscribed:timeline:#{account.id}")
     end
   end
+
+  private
+
+  def refresh_status_ids!
+    @announcement.status_ids = Status.from_text(@announcement.text).map(&:id)
+    @announcement.save
+  end
 end
diff --git a/db/migrate/20200312162302_add_status_ids_to_announcements.rb b/db/migrate/20200312162302_add_status_ids_to_announcements.rb
new file mode 100644
index 000000000..42aa6513d
--- /dev/null
+++ b/db/migrate/20200312162302_add_status_ids_to_announcements.rb
@@ -0,0 +1,6 @@
+class AddStatusIdsToAnnouncements < ActiveRecord::Migration[5.2]
+  def change
+    add_column :announcements, :status_ids, :bigint, array: true
+  end
+end
+
diff --git a/db/schema.rb b/db/schema.rb
index 7f28f2ec4..021ddac89 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -231,6 +231,7 @@ ActiveRecord::Schema.define(version: 2020_03_12_185443) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.datetime "published_at"
+    t.bigint "status_ids", array: true
   end
 
   create_table "backups", force: :cascade do |t|