Improve performance of follow recommendation scheduler (#16159)

Express follow_recommendations in terms of account_summaries rather than
accounts, integrate filters that are unconditionally used, and materialize
the resulting view.

This should result in the bulk of the computation being performed only once
instead of **once per recommendation language**.

1 files changed, 3 insertions, 2 deletions

diff --git a/app/workers/scheduler/follow_recommendations_scheduler.rb b/app/workers/scheduler/follow_recommendations_scheduler.rb
index 0a0286496..cb1e15961 100644
--- a/app/workers/scheduler/follow_recommendations_scheduler.rb
+++ b/app/workers/scheduler/follow_recommendations_scheduler.rb
@@ -14,13 +14,14 @@ class Scheduler::FollowRecommendationsScheduler
   def perform
     # Maintaining a materialized view speeds-up subsequent queries significantly
     AccountSummary.refresh
+    FollowRecommendation.refresh
 
-    fallback_recommendations = FollowRecommendation.safe.filtered.limit(SET_SIZE).index_by(&:account_id)
+    fallback_recommendations = FollowRecommendation.limit(SET_SIZE).index_by(&:account_id)
 
     I18n.available_locales.each do |locale|
       recommendations = begin
         if AccountSummary.safe.filtered.localized(locale).exists? # We can skip the work if no accounts with that language exist
-          FollowRecommendation.safe.filtered.localized(locale).limit(SET_SIZE).index_by(&:account_id)
+          FollowRecommendation.localized(locale).limit(SET_SIZE).index_by(&:account_id)
         else
           {}
         end