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John
John

Reputation: 6612

uniq returns other result than uniq_by

Until now I used uniq_by to count unique projectusers. But this method has been deprecated and the suggestion is to use uniq instead. But uniq_by returns 2 (correct!) and uniq returns 3 (not correct). The projectuser table is filled like this:

id,user_id
1,1
2,1
3,2

And here are the statements:

Projectuser.uniq_by {|p| p.user_id}.count --> 2
Projectuser.uniq {|p| p.user_id}.count --> 3

What do I need to change?

Upvotes: 1

Views: 205

Answers (3)

John
John

Reputation: 6612

I have it solved by using:

Projectuser.uniq.pluck(:user_id)

Upvotes: 0

Paulo Fidalgo
Paulo Fidalgo

Reputation: 22296

The result is rigth, since uniq is from Array. To match the uniqueness in SQL idiom you need to use distinct.

From the example from the documentation:

person.pets.select(:name).distinct
# => [#<Pet name: "Fancy-Fancy">]

Try:

Projectuser.select(:id, :user_id).distinct

Upvotes: 0

Meier
Meier

Reputation: 3880

The ActiveReord-Version of uniq seem to ignore the given block, and just check that the objects are uniq. If you look at the source you see that is just sets a flag.

See http://apidock.com/rails/ActiveRecord/QueryMethods/uniq

You can think of it as a modifier for the generated sql-statement.

Upvotes: 1

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