PERF: fixes N+1 for automation plugin (#32810)

- Add a safeguard until we implement pagination for the index, it
ensures we won't try to load more than 500 automations ever.
- Includes the fields of the automation so we don't have an N+1 and also
filter them in ruby land instead of doing two additional queries
- Ensures a field object in the field serializer is capable to find the
loaded automation associated to it instead of trying to reload it
- Includes pending_automations to avoid an N+1

plugins/automation/app/controllers/discourse_automation/admin_automations_controller.rb

@@ -5,7 +5,13 @@ module DiscourseAutomation
     requires_plugin DiscourseAutomation::PLUGIN_NAME
 
     def index
-      automations = DiscourseAutomation::Automation.order(:name).all
+      automations =
+        DiscourseAutomation::Automation
+          .strict_loading
+          .includes(:fields, :pending_automations)
+          .order(:name)
+          .limit(500)
+          .all
       serializer =
         ActiveModel::ArraySerializer.new(
           automations,
@@ -19,7 +25,8 @@ module DiscourseAutomation
     end
 
     def show
-      automation = DiscourseAutomation::Automation.find(params[:id])
+      automation =
+        DiscourseAutomation::Automation.includes(:fields, :pending_automations).find(params[:id])
       render_serialized_automation(automation)
     end
 
@@ -43,7 +50,8 @@ module DiscourseAutomation
     def update
       params.require(:automation)
 
-      automation = DiscourseAutomation::Automation.find(params[:id])
+      automation =
+        DiscourseAutomation::Automation.includes(:fields, :pending_automations).find(params[:id])
       if automation.scriptable.forced_triggerable
         params[:trigger] = automation.scriptable.forced_triggerable[:triggerable].to_s
       end

plugins/automation/app/models/discourse_automation/automation.rb

@@ -7,7 +7,8 @@ module DiscourseAutomation
     has_many :fields,
              class_name: "DiscourseAutomation::Field",
              dependent: :delete_all,
-             foreign_key: "automation_id"
+             foreign_key: "automation_id",
+             inverse_of: :automation
     has_many :pending_automations,
              class_name: "DiscourseAutomation::PendingAutomation",
              dependent: :delete_all,
@@ -28,6 +29,16 @@ module DiscourseAutomation
 
     attr_accessor :running_in_background
 
+    def trigger=(new_trigger)
+      @triggerable = nil
+      super
+    end
+
+    def script=(new_script)
+      @scriptable = nil
+      super
+    end
+
     def running_in_background!
       @running_in_background = true
     end

plugins/automation/app/models/discourse_automation/field.rb

@@ -4,7 +4,10 @@ module DiscourseAutomation
   class Field < ActiveRecord::Base
     self.table_name = "discourse_automation_fields"
 
-    belongs_to :automation, class_name: "DiscourseAutomation::Automation"
+    belongs_to :automation,
+               class_name: "DiscourseAutomation::Automation",
+               foreign_key: :automation_id,
+               inverse_of: :fields
 
     around_save :on_update_callback
 

plugins/automation/app/serializers/discourse_automation/automation_serializer.rb

@@ -61,7 +61,7 @@ module DiscourseAutomation
         not_found: scriptable.not_found,
         templates:
           process_templates(filter_fields_with_priority(scriptable.fields, object.trigger&.to_sym)),
-        fields: process_fields(object.fields.where(target: "script")),
+        fields: process_fields(script_fields),
       }
     end
 
@@ -80,7 +80,7 @@ module DiscourseAutomation
         doc: I18n.exists?(doc_key, :en) ? I18n.t(doc_key) : nil,
         not_found: triggerable&.not_found,
         templates: process_templates(triggerable&.fields || []),
-        fields: process_fields(object.fields.where(target: "trigger")),
+        fields: process_fields(trigger_fields),
         settings: triggerable&.settings,
       }
     end
@@ -141,6 +141,14 @@ module DiscourseAutomation
       ).as_json || []
     end
 
+    def script_fields
+      object.fields.select { |f| f.target == "script" }
+    end
+
+    def trigger_fields
+      object.fields.select { |f| f.target == "trigger" }
+    end
+
     def scriptable
       object.scriptable
     end

plugins/automation/config/locales/server.en.yml

@@ -5,7 +5,7 @@ en:
     models:
       fields:
         required_field: Field `%{name}` must be filled on `%{target}:%{target_name}`.
-        invalid_field: Field’s component `%{component}` is not usable on `%{target}:%{target_name}.`
+        invalid_field: Field’s component `%{component}` is not usable on `%{target}:%{target_name}`.
         invalid_metadata: Data for `%{field}` is invalid or component `%{component}` is unknown.
     triggerables:
       errors: