Batch Active Record Operations with `find_each`

Iterating over a collection of ActiveRecord models can incur a performance hit to your application, especially when the result set is large.

A basic query like all or where could return tens of thousand of records. When that query returns, it will instantiate your records all at once, loading them into memory, and potentially leading to instability. Luckily if we need to operate on a large result set, we can use the find_each method to work in batches on our query.

find_each works by using the find_in_batches method under the hood, with a default batch size of 1000.

# This is bad ❌
Customer.where(active: true).each do |customer|
  # ....
end

# This is good ☑️
Customer.where(active: true).find_each do |customer|
  # ....
end

If you need to, you can also adjust the batch size by passing the batch_size kwarg to find_each

Customer.where(active: true).find_each(batch_size: 2000) do |customer|
  # ...
end

https://devdocs.io/rails~6.1/activerecord/batches#method-i-find_each

H/T https://rails.rubystyle.guide/