Change follow recommendation materialized view to be faster in most cases (#26545)

Co-authored-by: Renaud Chaput <renchap@gmail.com>

app/models/follow_recommendation.rb

@@ -2,7 +2,7 @@
 
 # == Schema Information
 #
-# Table name: follow_recommendations
+# Table name: global_follow_recommendations
 #
 #  account_id :bigint(8)        primary key
 #  rank       :decimal(, )
@@ -11,6 +11,7 @@
 
 class FollowRecommendation < ApplicationRecord
   self.primary_key = :account_id
+  self.table_name = :global_follow_recommendations
 
   belongs_to :account_summary, foreign_key: :account_id, inverse_of: false
   belongs_to :account

db/migrate/20230818141056_create_global_follow_recommendations.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class CreateGlobalFollowRecommendations < ActiveRecord::Migration[7.0]
+  def change
+    create_view :global_follow_recommendations, materialized: { no_data: true }
+    safety_assured { add_index :global_follow_recommendations, :account_id, unique: true }
+  end
+end

db/post_migrate/20230818142253_drop_follow_recommendations.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class DropFollowRecommendations < ActiveRecord::Migration[7.0]
+  def up
+    drop_view :follow_recommendations, materialized: true
+  end
+
+  def down
+    create_view :follow_recommendations, version: 2, materialized: { no_data: true }
+    safety_assured { add_index :follow_recommendations, :account_id, unique: true }
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_08_14_223300) do
+ActiveRecord::Schema[7.0].define(version: 2023_08_18_142253) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -1331,34 +1331,36 @@ ActiveRecord::Schema[7.0].define(version: 2023_08_14_223300) do
   SQL
   add_index "account_summaries", ["account_id"], name: "index_account_summaries_on_account_id", unique: true
 
-  create_view "follow_recommendations", materialized: true, sql_definition: <<-SQL
+  create_view "global_follow_recommendations", materialized: true, sql_definition: <<-SQL
       SELECT t0.account_id,
       sum(t0.rank) AS rank,
       array_agg(t0.reason) AS reason
      FROM ( SELECT account_summaries.account_id,
               ((count(follows.id))::numeric / (1.0 + (count(follows.id))::numeric)) AS rank,
               'most_followed'::text AS reason
-             FROM (((follows
+             FROM ((follows
                JOIN account_summaries ON ((account_summaries.account_id = follows.target_account_id)))
                JOIN users ON ((users.account_id = follows.account_id)))
-               LEFT JOIN follow_recommendation_suppressions ON ((follow_recommendation_suppressions.account_id = follows.target_account_id)))
-            WHERE ((users.current_sign_in_at >= (now() - 'P30D'::interval)) AND (account_summaries.sensitive = false) AND (follow_recommendation_suppressions.id IS NULL))
+            WHERE ((users.current_sign_in_at >= (now() - 'P30D'::interval)) AND (account_summaries.sensitive = false) AND (NOT (EXISTS ( SELECT 1
+                     FROM follow_recommendation_suppressions
+                    WHERE (follow_recommendation_suppressions.account_id = follows.target_account_id)))))
             GROUP BY account_summaries.account_id
            HAVING (count(follows.id) >= 5)
           UNION ALL
            SELECT account_summaries.account_id,
               (sum((status_stats.reblogs_count + status_stats.favourites_count)) / (1.0 + sum((status_stats.reblogs_count + status_stats.favourites_count)))) AS rank,
               'most_interactions'::text AS reason
-             FROM (((status_stats
+             FROM ((status_stats
                JOIN statuses ON ((statuses.id = status_stats.status_id)))
                JOIN account_summaries ON ((account_summaries.account_id = statuses.account_id)))
-               LEFT JOIN follow_recommendation_suppressions ON ((follow_recommendation_suppressions.account_id = statuses.account_id)))
-            WHERE ((statuses.id >= (((date_part('epoch'::text, (now() - 'P30D'::interval)) * (1000)::double precision))::bigint << 16)) AND (account_summaries.sensitive = false) AND (follow_recommendation_suppressions.id IS NULL))
+            WHERE ((statuses.id >= (((date_part('epoch'::text, (now() - 'P30D'::interval)) * (1000)::double precision))::bigint << 16)) AND (account_summaries.sensitive = false) AND (NOT (EXISTS ( SELECT 1
+                     FROM follow_recommendation_suppressions
+                    WHERE (follow_recommendation_suppressions.account_id = statuses.account_id)))))
             GROUP BY account_summaries.account_id
            HAVING (sum((status_stats.reblogs_count + status_stats.favourites_count)) >= (5)::numeric)) t0
     GROUP BY t0.account_id
     ORDER BY (sum(t0.rank)) DESC;
   SQL
-  add_index "follow_recommendations", ["account_id"], name: "index_follow_recommendations_on_account_id", unique: true
+  add_index "global_follow_recommendations", ["account_id"], name: "index_global_follow_recommendations_on_account_id", unique: true
 
 end

db/views/global_follow_recommendations_v01.sql

@@ -0,0 +1,32 @@
+SELECT
+  account_id,
+  sum(rank) AS rank,
+  array_agg(reason) AS reason
+FROM (
+  SELECT
+    account_summaries.account_id AS account_id,
+    count(follows.id) / (1.0 + count(follows.id)) AS rank,
+    'most_followed' AS reason
+  FROM follows
+  INNER JOIN account_summaries ON account_summaries.account_id = follows.target_account_id
+  INNER JOIN users ON users.account_id = follows.account_id
+  WHERE users.current_sign_in_at >= (now() - interval '30 days')
+    AND account_summaries.sensitive = 'f'
+    AND NOT EXISTS (SELECT 1 FROM follow_recommendation_suppressions WHERE follow_recommendation_suppressions.account_id = follows.target_account_id)
+  GROUP BY account_summaries.account_id
+  HAVING count(follows.id) >= 5
+  UNION ALL
+  SELECT account_summaries.account_id AS account_id,
+         sum(status_stats.reblogs_count + status_stats.favourites_count) / (1.0 + sum(status_stats.reblogs_count + status_stats.favourites_count)) AS rank,
+         'most_interactions' AS reason
+  FROM status_stats
+  INNER JOIN statuses ON statuses.id = status_stats.status_id
+  INNER JOIN account_summaries ON account_summaries.account_id = statuses.account_id
+  WHERE statuses.id >= ((date_part('epoch', now() - interval '30 days') * 1000)::bigint << 16)
+    AND account_summaries.sensitive = 'f'
+    AND NOT EXISTS (SELECT 1 FROM follow_recommendation_suppressions WHERE follow_recommendation_suppressions.account_id = statuses.account_id)
+  GROUP BY account_summaries.account_id
+  HAVING sum(status_stats.reblogs_count + status_stats.favourites_count) >= 5
+) t0
+GROUP BY account_id
+ORDER BY rank DESC