Is there a way to use group to select the id's of the grouped records in Rails?

Question

Purchase.all.group( :user_id ).sum( :price )

This returns

[{ 1 : 234 }, { 2 : 345 }, ...

Is it possible to pull the Purchase ids?

For example, suppose the first group returned:

{ user_id : 1, price : 234, ids : [3,6,9] }

Answer 1

Using postgresql, you can use array_agg:

Purchase.select('user_id, sum(price) as price, array_agg(id) as ids').group('user_id')