Pessimistic locking fails

Question

I have the following code in my controller:

Item.transaction do
  item = JobDistribution.lock(true).find(params[:id])
  item.update_attributes(status: JobDistribution.statuses[:processing])
  respond_to do |format|
    format.json { render :json => "object processing", status: :success }
  end
end

but when I run the code I'm getting the error:

Attempted to update a stale object: Item

I don't understand why, I followed the rails documentation.

From which documentation do you have this? You are trying to override new data with old, while the new is locked. — Robin, Nov 04 '15 at 12:07
@Robin http://api.rubyonrails.org/classes/ActiveRecord/Locking/Pessimistic.html — bl0b, Nov 04 '15 at 12:41
Do you have a `lock_version` column? Is it the latest number, when you try to run your transaction? — Robin, Nov 04 '15 at 12:56
@Robin I do have a lock version column and here is the failing sql query: `UPDATE "items" SET "status" = 1, "updated_at" = '2015-11-04 11:54:36.422768', "lock_version" = 1 WHERE ("items"."id" = 35 AND "items"."lock_version" = 0)` — bl0b, Nov 04 '15 at 13:03

score 3 · Accepted Answer · answered Nov 04 '15 at 16:14

3

lock_version is for optimistic locking, you're also using pessimistic locking with chaining your find from the lock. Rails is getting confused between the two - pick one or the other.

answered Nov 04 '15 at 16:14

smathy

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Pessimistic locking fails

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