How to tell if already within a database transaction in ruby on rails?

You can use

ActiveRecord::Base.connection.open_transactions

to see if your method is executed in a transaction.

ActiveRecord::Base.connection.open_transactions == 0 implies that your method is not executed in a transaction. Anything greater than 0 would imply that your method is executed in a transaction. For example ActiveRecord::Base.connection.open_transactions > 0

Update:

from rails documentation

all database statements in the nested transaction block become part of the parent transaction

So number of open transaction will be one even if you are in a nested transaction.

This is what i got in my console

ActiveRecord::Base.transaction do   User.first.update_attribute(:first_name, "something")   ActiveRecord::Base.transaction do       User.first.update_attribute(:last_name, "something")       p ActiveRecord::Base.connection.open_transactions   endend  (0.3ms)  BEGIN  User Load (0.8ms)  SELECT "users".* FROM "users" LIMIT 1  (0.8ms)  UPDATE "users" SET "first_name" = 'something', "updated_at" = '2013-11-20 18:33:52.254088' WHERE "users"."id" = 1  User Load (0.5ms)  SELECT "users".* FROM "users" LIMIT 1  (0.4ms)  UPDATE "users" SET "last_name" = 'something', "updated_at" = '2013-11-20 18:33:52.266976' WHERE "users"."id" = 1  1  (14.2ms)  COMMIT  => 1 

In Rails 6.0 you can use:

ActiveRecord::Base.connection.transaction_open?