Improve FDW performance with a workaround

ee/app/controllers/admin/geo_projects_controller.rb

@@ -11,7 +11,11 @@ class Admin::GeoProjectsController < Admin::ApplicationController
 
     case params[:sync_status]
     when 'never'
-      @projects = finder.never_synced_projects.page(params[:page])
+      # This method uses FDW heavily and due to optimizations we need to inject the pagination
+      # earlier as well, so we need the block to do that
+      @projects = finder.never_synced_projects do |fdw_relation|
+        fdw_relation.page(params[:page])
+      end.page(params[:page])
     when 'failed'
       @registries = finder.failed_projects.page(params[:page])
     when 'pending'

ee/app/finders/geo/project_registry_status_finder.rb

@@ -63,16 +63,23 @@ module Geo
     # We include here both projects without a corresponding ProjectRegistry
     # or projects that have never successfully synced.
     #
+    # @yield [ActiveRecord::Relation]
     # @return [Geo::Fdw::Project] Projects that has never been fully synced
     def never_synced_projects
       no_project_registry = project_registry[:project_id].eq(nil)
       no_repository_synced = project_registry[:last_repository_successful_sync_at].eq(nil)
 
-      Geo::Fdw::Project.joins("LEFT OUTER JOIN project_registry ON (project_registry.project_id = #{Geo::Fdw::Project.table_name}.id)")
+      project_ids = Geo::Fdw::Project.select(:id).joins("LEFT OUTER JOIN project_registry ON (project_registry.project_id = #{Geo::Fdw::Project.table_name}.id)")
         .where(
           no_project_registry
-            .or(no_repository_synced)
-        ).includes(:project_registry)
+            .or(no_repository_synced))
+
+      # This allows us to inject pagination
+      if block_given?
+        project_ids = yield(project_ids)
+      end
+
+      Project.where(id: project_ids.to_a).includes(:project_registry)
     end
 
     private

ee/spec/finders/geo/project_registry_status_finder_spec.rb

@@ -62,16 +62,12 @@ describe Geo::ProjectRegistryStatusFinder, :geo do
 
   describe '#never_synced_projects' do
     it 'returns only FDW projects without registry or with never synced registries' do
-      fdw_project_with_never_synced_registry_with_failure = Geo::Fdw::Project.find(never_synced_registry_with_failure.project.id)
-      fdw_project_with_never_synced_registry = Geo::Fdw::Project.find(project_with_never_synced_registry.id)
-      fdw_project_without_registry = Geo::Fdw::Project.find(project_without_registry.id)
-
       result = subject.never_synced_projects
 
       expect(result).to contain_exactly(
-        fdw_project_without_registry,
-        fdw_project_with_never_synced_registry,
-        fdw_project_with_never_synced_registry_with_failure
+        project_without_registry,
+        project_with_never_synced_registry,
+        never_synced_registry_with_failure.project
       )
     end
   end