Active Records support optimistic locking if the field lock_version is present. Each update to the record increments the lock_version column and the locking facilities ensure that records instantiated twice will let the last one saved raise a StaleObjectError if the first was also updated. Example:

  p1 = Person.find(1)
  p2 = Person.find(1)

  p1.first_name = "Michael"

  p2.first_name = "should fail"
  p2.save # Raises a ActiveRecord::StaleObjectError

You’re then responsible for dealing with the conflict by rescuing the exception and either rolling back, merging, or otherwise apply the business logic needed to resolve the conflict.

You must ensure that your database schema defaults the lock_version column to 0.

This behavior can be turned off by setting ActiveRecord::Base.lock_optimistically = false.

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