Add index to good_jobs to improve querying candidate jobs

lib/generators/good_job/templates/install/migrations/create_good_jobs.rb.erb

@@ -41,5 +41,7 @@ class CreateGoodJobs < ActiveRecord::Migration<%= migration_version %>
     add_index :good_jobs, [:cron_key, :cron_at], name: :index_good_jobs_on_cron_key_and_cron_at, unique: true
     add_index :good_jobs, [:active_job_id], name: :index_good_jobs_on_active_job_id
     add_index :good_jobs, [:finished_at], where: "retried_good_job_id IS NULL AND finished_at IS NOT NULL", name: :index_good_jobs_jobs_on_finished_at
+    add_index :good_jobs, [:priority, :created_at], order: { priority: "DESC NULLS LAST", created_at: :asc },
+      where: "finished_at IS NULL", name: :index_good_jobs_jobs_on_priority_created_at_when_unfinished
   end
 end

lib/generators/good_job/templates/update/migrations/03_create_index_good_jobs_jobs_on_priority_created_at_when_unfinished.rb.erb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+class CreateIndexGoodJobsJobsOnPriorityCreatedAtWhenUnfinished < ActiveRecord::Migration<%= migration_version %>
+  disable_ddl_transaction!
+
+   def change
+    reversible do |dir|
+      dir.up do
+        # Ensure this incremental update migration is idempotent
+        # with monolithic install migration.
+        return if connection.index_name_exists?(:good_jobs, :index_good_jobs_jobs_on_priority_created_at_when_unfinished)
+      end
+    end
+
+    add_index :good_jobs, [:priority, :created_at], order: { priority: "DESC NULLS LAST", created_at: :asc },
+      where: "finished_at IS NULL", name: :index_good_jobs_jobs_on_priority_created_at_when_unfinished,
+      algorithm: :concurrently
+  end
+end

spec/test_app/db/migrate/20221019021425_create_index_good_jobs_jobs_on_priority_created_at_when_unfinished.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+class CreateIndexGoodJobsJobsOnPriorityCreatedAtWhenUnfinished < ActiveRecord::Migration[6.1]
+  disable_ddl_transaction!
+
+   def change
+    reversible do |dir|
+      dir.up do
+        # Ensure this incremental update migration is idempotent
+        # with monolithic install migration.
+        return if connection.index_name_exists?(:good_jobs, :index_good_jobs_jobs_on_priority_created_at_when_unfinished)
+      end
+    end
+
+    add_index :good_jobs, [:priority, :created_at], order: { priority: "DESC NULLS LAST", created_at: :asc },
+      where: "finished_at IS NULL", name: :index_good_jobs_jobs_on_priority_created_at_when_unfinished,
+      algorithm: :concurrently
+  end
+end

spec/test_app/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: 2022_07_20_154438) do
+ActiveRecord::Schema.define(version: 2022_10_19_021425) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
@@ -51,6 +51,7 @@
     t.index ["cron_key", "created_at"], name: "index_good_jobs_on_cron_key_and_created_at"
     t.index ["cron_key", "cron_at"], name: "index_good_jobs_on_cron_key_and_cron_at", unique: true
     t.index ["finished_at"], name: "index_good_jobs_jobs_on_finished_at", where: "((retried_good_job_id IS NULL) AND (finished_at IS NOT NULL))"
+    t.index ["priority", "created_at"], name: "index_good_jobs_jobs_on_priority_created_at_when_unfinished", order: { priority: "DESC NULLS LAST" }, where: "(finished_at IS NULL)"
     t.index ["queue_name", "scheduled_at"], name: "index_good_jobs_on_queue_name_and_scheduled_at", where: "(finished_at IS NULL)"
     t.index ["scheduled_at"], name: "index_good_jobs_on_scheduled_at", where: "(finished_at IS NULL)"
   end