Change index on follows table to improve performance of some queries (#36374)

db/migrate/20251007100627_add_index_follows_on_target_account_id_and_account_id.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddIndexFollowsOnTargetAccountIdAndAccountId < ActiveRecord::Migration[8.0]
+  disable_ddl_transaction!
+
+  def change
+    add_index :follows, [:target_account_id, :account_id], algorithm: :concurrently
+  end
+end

db/migrate/20251007100813_remove_index_follows_on_target_account_id.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class RemoveIndexFollowsOnTargetAccountId < ActiveRecord::Migration[8.0]
+  disable_ddl_transaction!
+
+  def change
+    remove_index :follows, [:target_account_id], algorithm: :concurrently
+  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[8.0].define(version: 2025_10_02_140103) do
+ActiveRecord::Schema[8.0].define(version: 2025_10_07_100813) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_catalog.plpgsql"
 
@@ -571,7 +571,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_10_02_140103) do
     t.boolean "notify", default: false, null: false
     t.string "languages", array: true
     t.index ["account_id", "target_account_id"], name: "index_follows_on_account_id_and_target_account_id", unique: true
-    t.index ["target_account_id"], name: "index_follows_on_target_account_id"
+    t.index ["target_account_id", "account_id"], name: "index_follows_on_target_account_id_and_account_id"
   end
 
   create_table "generated_annual_reports", force: :cascade do |t|