I have a query that returns a 2d array, but would like it to return a 1d array of results. Given:
sql = "SELECT `id` FROM things WHERE other_id = 8" ids = ActiveRecord::Base.connection.execute(sql).to_a
ids is then equal to
[[1],[2],[3],[4],[5],[9]....]
I was using map to create a new array, but it was terribly slow with more than 5000 records. What is the fastest method of obtaining the following format:
[1,2,3,4,5,9...]
You can do as
sql = "SELECT `id` FROM things WHERE other_id = 8"
ids = ActiveRecord::Base.connection.execute(sql).to_a.flatten
More Rails way is to use #pluck as below :-
Thing.where(other_id: 8).pluck(:id)
pluck is the way to go here.
Why do you use the execute statement? Use an ActiveRecord model.
Thing.where(other_id: 8).pluck(:id)
# => [1, 2, 3, 4]
Assuming your models and associations are set up correctly, i.e.
class Thing < ActiveRecord::Base
belongs_to :other
end
class Other < ActiveRecord::Base
has_many :things
end
you can use ids:
Thing.where(other_id: 8).ids #=> [1, 2, 3, 4, 5, 9 ...]
or, coming from Other:
Other.find(8).things.ids #=> [1, 2, 3, 4, 5, 9 ...]
or:
Other.find(8).thing_ids #=> [1, 2, 3, 4, 5, 9 ...]
thing_ids is the cute one.. :D
ids to iterate on, or build a subquery, there are far better ways of doing this. Just trying to help, even if that's a bit beyond the scope of the question.