Module: ActiveRecord::Locking::Optimistic
- Extended by:
- ActiveSupport::Concern
- Included in:
- Base
- Defined in:
- lib/rubypitaya/app-template/vendor/bundle/ruby/3.1.0/gems/activerecord-7.0.4/lib/active_record/locking/optimistic.rb
Overview
What is Optimistic Locking
Optimistic locking allows multiple users to access the same record for edits, and assumes a minimum of conflicts with the data. It does this by checking whether another process has made changes to a record since it was opened, an ActiveRecord::StaleObjectError
exception is thrown if that has occurred and the update is ignored.
Check out ActiveRecord::Locking::Pessimistic
for an alternative.
Usage
Active Record supports optimistic locking if the lock_version
field 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"
p1.save
p2.first_name = "should fail"
p2.save # Raises an ActiveRecord::StaleObjectError
Optimistic locking will also check for stale data when objects are destroyed. Example:
p1 = Person.find(1)
p2 = Person.find(1)
p1.first_name = "Michael"
p1.save
p2.destroy # Raises an 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.
This locking mechanism will function inside a single Ruby process. To make it work across all web requests, the recommended approach is to add lock_version
as a hidden field to your form.
This behavior can be turned off by setting ActiveRecord::Base.lock_optimistically = false
. To override the name of the lock_version
column, set the locking_column
class attribute:
class Person < ActiveRecord::Base
self.locking_column = :lock_person
end
Defined Under Namespace
Modules: ClassMethods
Instance Method Summary collapse
-
#increment! ⇒ Object
:nodoc:.
-
#locking_enabled? ⇒ Boolean
:nodoc:.
Methods included from ActiveSupport::Concern
append_features, class_methods, extended, included, prepend_features, prepended
Instance Method Details
#increment! ⇒ Object
:nodoc:
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# File 'lib/rubypitaya/app-template/vendor/bundle/ruby/3.1.0/gems/activerecord-7.0.4/lib/active_record/locking/optimistic.rb', line 63 def increment!(*, **) # :nodoc: super.tap do if locking_enabled? self[self.class.locking_column] += 1 clear_attribute_change(self.class.locking_column) end end end |
#locking_enabled? ⇒ Boolean
:nodoc:
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# File 'lib/rubypitaya/app-template/vendor/bundle/ruby/3.1.0/gems/activerecord-7.0.4/lib/active_record/locking/optimistic.rb', line 59 def locking_enabled? # :nodoc: self.class.locking_enabled? end |