Benito Serna Tips and tools for Ruby on Rails developers

Code to run the examples for preload, includes or eager_load

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:

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

Do you feel bad for asking for help to fix an n+1 queries problem?

Making things work isn't enough for you any more? Now you need to consider performance and scalability?

... But you normally have troubles fixing n+1 queries and trying to find why active record is ignoring your "includes"?

Are you are worried because you feel unqualified to tackle tasks with complex data models?

Sign up to learn how to fix n+1 queries on Rails