Question

I have associated models like this:

class Batch
  has_many :logs

class Log
  belongs_to :batch

I’m using includes to load batches with logs:

b = Batch.includes(:logs)

Which runs 2 selects as expected (batches and logs).

Then I do

b.first.logs.first.batch

and this triggers another select on batches, even when they were actually loaded already.
I figured to “fix” it by doing includes(:logs => :batch) but I’m still thinking that something is wrong here because the same batches are loaded twice. What gives?

Answer 1

You can fix this with the :inverse_of setting, which lets ActiveRecord know that the two associations are the inverse of each other.

class Batch
  has_many :logs, :inverse_of => :batch
end

class Log
  belongs_to :batch, :inverse_of => :logs
end