module Sequel::Plugins::MssqlOptimisticLocking

This plugin implements optimistic locking mechanism on Microsoft SQL Server using a timestamp/rowversion column to ensure that concurrent updates are detected and previous changes are not automatically overridden. This is best implemented by a code example:

class Person < Sequel::Model
  plugin :mssql_optimistic_locking
end
p1 = Person[1]
p2 = Person[1]
p1.update(name: 'Jim') # works
p2.update(name: 'Bob') # raises Sequel::NoExistingObject

In order for this plugin to work, you need to make sure that the database table has a column of timestamp or rowversion. The plugin uses a default name of timestamp for this columns, but you can override that using the :lock_column option:

plugin :mssql_optimistic_locking, lock_column: :column_name

By default, the plugin allows using the lock column setter method to either increase or decrease the lock column value. To prevent increases, which could potentially be used to skip an update when it update should be made, you can use the :prevent_increase plugin option:

plugin :mssql_optimistic_locking, prevent_increase: true

This plugin relies on the instance_filters plugin.

Public Class Methods

apply (model, opts=OPTS)

Source

   # File lib/sequel/plugins/mssql_optimistic_locking.rb
35 def self.apply(model, opts=OPTS)
36   model.plugin(:optimistic_locking_base)
37 end

Load the instance_filters plugin into the model.

configure (model, opts=OPTS)

Source

   # File lib/sequel/plugins/mssql_optimistic_locking.rb
40 def self.configure(model, opts=OPTS)
41   model.lock_column = opts[:lock_column] || model.lock_column || :timestamp
42   # SEQUEL6: Make prevent_increase true by default
43   model.send(:prevent_lock_column_increase!) if opts[:prevent_increase]
44 end

Set the lock column