Do you know “in theory” the difference between “includes”, “preload”, “eager_load” and “joins”, but you still think that you need more examples to really understand how to use them?

Here you will find a set of examples to help you understand how you can use this 4 methods.

You can find the code on bhserna/preloading_examples

This is the code that I used for the post: Examples to learn the difference between preload, includes or eager_load.

On lib/examples.rb you will find a list of examples with:

• The description of a task
• The query written with ActiveRecord
• A function to write the results

You can use this code to play a little more and try different things.

How to run the examples

1. Create a postgres database with createdb preloading_examples. As you can see the in db/config.rb the name of the database is hardcoded, so you will need to create a database with that name.

2. Install the dependencies with bundle install.

3. Run the seeds with ruby db/seeds.rb. You can also update the data that you want to use, there.

4. Run the examples with ruby lib/examples.rb.

Related articles

• What to do when you need a button_to within a form in Rails
• Active Record Playground Runner Introduction
• Tool to run the examples for the 5 ways to fetch the latest-n-of-each record
• When is better to use preload or eager_load vs includes?