From cdcd437e738eba0770778e6e5387269c6d946647 Mon Sep 17 00:00:00 2001
From: Michael Fowler <mkrfowler@gmail.com>
Date: Thu, 5 Jan 2023 14:58:06 +1300
Subject: [PATCH] Avoid including unnecessary pg_locks references when counting
 jobs

Previously, the executed query for in particular the `succeeded` scope included
a join against `pg_locks`.  This is not particularly useful, and unfortunately
triggers evaluation of that join criterion, with noticable expense as job volume
grows.

This change modifies the jobs filter logic to only include those joins in the
necessary locations (`running`) and when loading records for practical
enumeration.
---
 app/filters/good_job/base_filter.rb | 6 +++++-
 app/filters/good_job/jobs_filter.rb | 8 ++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/app/filters/good_job/base_filter.rb b/app/filters/good_job/base_filter.rb
index 84d4bc0b7..090d4d7dd 100644
--- a/app/filters/good_job/base_filter.rb
+++ b/app/filters/good_job/base_filter.rb
@@ -14,7 +14,7 @@ def initialize(params, base_query = nil)
     def records
       after_scheduled_at = params[:after_scheduled_at].present? ? Time.zone.parse(params[:after_scheduled_at]) : nil
 
-      filtered_query.display_all(
+      query_for_records.display_all(
         after_scheduled_at: after_scheduled_at,
         after_id: params[:after_id]
       ).limit(params.fetch(:limit, DEFAULT_LIMIT))
@@ -62,6 +62,10 @@ def filtered_count
 
     private
 
+    def query_for_records
+      raise NotImplementedError
+    end
+
     def default_base_query
       raise NotImplementedError
     end
diff --git a/app/filters/good_job/jobs_filter.rb b/app/filters/good_job/jobs_filter.rb
index c84472302..d8985943a 100644
--- a/app/filters/good_job/jobs_filter.rb
+++ b/app/filters/good_job/jobs_filter.rb
@@ -2,7 +2,7 @@
 module GoodJob
   class JobsFilter < BaseFilter
     def states
-      query = filtered_query(params.except(:state)).unscope(:select)
+      query = filtered_query(params.except(:state))
       {
         'scheduled' =>  query.scheduled.count,
         'retried' => query.retried.count,
@@ -14,7 +14,7 @@ def states
     end
 
     def filtered_query(filter_params = params)
-      query = base_query.includes(:executions).includes_advisory_locks
+      query = base_query
 
       query = query.job_class(filter_params[:job_class]) if filter_params[:job_class].present?
       query = query.where(queue_name: filter_params[:queue_name]) if filter_params[:queue_name].present?
@@ -47,6 +47,10 @@ def filtered_count
 
     private
 
+    def query_for_records
+      filtered_query.includes(:executions).includes_advisory_locks
+    end
+
     def default_base_query
       GoodJob::Job.all
     end