From 7052280d1c9d625ff83d86e68b665e934a537ef1 Mon Sep 17 00:00:00 2001
From: Martin Meyerhoff <mamhoff@gmail.com>
Date: Wed, 19 Jul 2023 17:28:56 +0200
Subject: [PATCH] Define #preload_relations on Ingredients

In order to be able to preload ingredients' related object graphs, we
need to be able to tell the rails preloader how those graphs look.

This adds a method that can be used on for example an element like this:

```
def preload_ingredient_relations(element)
  element.ingredients.group_by(&:preload_relations).each do |preload_relations, ingredients|
    preload(records: ingredients.map(&:related_object).compact, associations: preload_relations)
  end
  element
end

def preload(records:, associations:)
  if Rails::VERSION::MAJOR >= 7
    ActiveRecord::Associations::Preloader.new(records: records, associations: associations).call
  else
    ActiveRecord::Associations::Preloader.new.preload(records, associations)
  end
end
```

Most notorious for n+1 problems is the picture ingredient that tends to
have a lot of thumbs that we actually need.
---
 app/models/alchemy/ingredient.rb                | 6 ++++++
 app/models/alchemy/ingredients/picture.rb       | 4 ++++
 spec/models/alchemy/ingredient_spec.rb          | 8 ++++++++
 spec/models/alchemy/ingredients/picture_spec.rb | 8 ++++++++
 4 files changed, 26 insertions(+)

diff --git a/app/models/alchemy/ingredient.rb b/app/models/alchemy/ingredient.rb
index 7228abe8e0..6ef01ae1bf 100644
--- a/app/models/alchemy/ingredient.rb
+++ b/app/models/alchemy/ingredient.rb
@@ -90,6 +90,12 @@ def allowed_settings
       end
     end
 
+    # This method can be overwritten in individual ingredients to fetch objects that belong to the related object in some form.
+    # This takes an Array of things that can be passed to the Rails preloader.
+    def preload_relations
+      []
+    end
+
     # The value or the related object if present
     def value
       related_object || self[:value]
diff --git a/app/models/alchemy/ingredients/picture.rb b/app/models/alchemy/ingredients/picture.rb
index 378dd694f5..9bbdbd7773 100644
--- a/app/models/alchemy/ingredients/picture.rb
+++ b/app/models/alchemy/ingredients/picture.rb
@@ -38,6 +38,10 @@ class Picture < Alchemy::Ingredient
         upsample
       ]
 
+      def preload_relations
+        [:thumbs]
+      end
+
       # The first 30 characters of the pictures name
       #
       # Used by the Element#preview_text method.
diff --git a/spec/models/alchemy/ingredient_spec.rb b/spec/models/alchemy/ingredient_spec.rb
index 364b04a1ad..5b883fe370 100644
--- a/spec/models/alchemy/ingredient_spec.rb
+++ b/spec/models/alchemy/ingredient_spec.rb
@@ -213,4 +213,12 @@
       )
     end
   end
+
+  describe "#preload_relations" do
+    let(:ingredient) { Alchemy::Ingredients::Text.new(role: "intro", element: element) }
+
+    subject { ingredient.preload_relations }
+
+    it { is_expected.to eq([]) }
+  end
 end
diff --git a/spec/models/alchemy/ingredients/picture_spec.rb b/spec/models/alchemy/ingredients/picture_spec.rb
index da1b4182b0..98b63bb318 100644
--- a/spec/models/alchemy/ingredients/picture_spec.rb
+++ b/spec/models/alchemy/ingredients/picture_spec.rb
@@ -125,4 +125,12 @@
       )
     end
   end
+
+  describe "#preload_relations" do
+    let(:ingredient) { described_class.new }
+
+    subject { ingredient.preload_relations }
+
+    it { is_expected.to eq([:thumbs]) }
+  end
 end