[index] Add index on polls id and lock_version

db/migrate/20210117210100_add_index_on_polls.rb

@@ -0,0 +1,7 @@
+class AddIndexOnPolls < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_index :polls, [:id, :lock_version], 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.define(version: 2021_01_17_120100) do
+ActiveRecord::Schema.define(version: 2021_01_17_210100) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"
@@ -571,6 +571,7 @@ ActiveRecord::Schema.define(version: 2021_01_17_120100) do
     t.datetime "updated_at", null: false
     t.integer "lock_version", default: 0, null: false
     t.index ["account_id"], name: "index_polls_on_account_id"
+    t.index ["id", "lock_version"], name: "index_polls_on_id_and_lock_version"
     t.index ["status_id"], name: "index_polls_on_status_id"
   end