How to get last N records with activerecord?

Question

With :limit in query, I will get first N records. What is the easiest way to get last N records?

Answer 1

In my rails (rails 4.2) project, I use

Model.last(10) # get the last 10 record order by id

and it works.

Answer 2

For Rails 5 (and likely Rails 4)

Bad:

Something.last(5)

because:

Something.last(5).class
=> Array

so:

Something.last(50000).count

will likely blow up your memory or take forever.

Good approach:

Something.limit(5).order('id desc')

because:

Something.limit(5).order('id desc').class
=> Image::ActiveRecord_Relation

Something.limit(5).order('id desc').to_sql
=> "SELECT  \"somethings\".* FROM \"somethings\" ORDER BY id desc LIMIT 5"

The latter is an unevaluated scope. You can chain it, or convert it to an array via .to_a. So:

Something.limit(50000).order('id desc').count

... takes a second.

Answer 3

Add an :order parameter to the query

Answer 4

If you have a default scope in your model that specifies an ascending order in Rails 3 you'll need to use reorder rather than order as specified by Arthur Neves above:

Something.limit(5).reorder('id desc')

or

Something.reorder('id desc').limit(5)

Answer 5

This is the Rails 3 way

SomeModel.last(5) # last 5 records in ascending order

SomeModel.last(5).reverse # last 5 records in descending order

Answer 6

For Rails 4 and above version:

You can try something like this If you want first oldest entry

YourModel.order(id: :asc).limit(5).each do |d|

---

You can try something like this if you want last latest entries..

YourModel.order(id: :desc).limit(5).each do |d|