Arel ActiveRecord extensions

arel_activerecord_extensions.rb

module DatabaseOperations
  module Function
    module_function
    def coalesce(*args)
      Arel::Nodes::NamedFunction.new('COALESCE', args)
    end
  end

  module Atomic
    def atomic_increment(name, count = 1)
      col = self.class.arel_table[name]
      increment_col = Arel::Nodes::Grouping.new(
        Arel::Nodes::Addition.new(Function.coalesce(col, 0), count)
      )
      colname = self.class.connection.quote_column_name(name)
      updates = self.class.sanitize_sql_for_assignment("#{colname} = #{increment_col.to_sql}")
      write_attribute(name, self[name] + count) # the ol' college try
      self.clear_attribute_changes([name])
      update_self(updates)
    end
    private

    def update_self(*args)
      primary_key = self.class.primary_key
      self.class.unscoped.where(primary_key => self[primary_key]).update_all(args)
    end
  end

  ActiveSupport.on_load(:active_record) do
    include Atomic
  end
end