Apply rails/rails#18846 for Delayed Job workers

initializer.rb

Delayed::Worker.lifecycle.before :execute do
  require 'active_record/relation/warn_on_result_set_size'
  ActiveRecord::Base.warn_on_result_set_size = 1001
  ActiveRecord::Base.logger = Rails.logger
  ActiveRecord::Base.logger.level = Logger::WARN
end

warn_on_result_set_size.rb

module ActiveRecord
  class Relation
    module WarnOnResultSetSize
      # When this module is prepended to `ActiveRecord::Relation` and
      # `config.active_record.warn_on_result_set_size` is set to an
      # integer, if the number of records a query returns is greater
      # than the value of `warn_on_result_set_size`, a warning is
      # logged. This allows for the dection of queries that return a
      # large number of records, which could cause memory bloat.
      def exec_queries
        super.tap do
          if logger && warn_on_result_set_size
            if @records.length >= warn_on_result_set_size
              logger.warn "Result set size exceeded #{warn_on_result_set_size} (model: #{@klass}, records: #{@records.size})"
            end
          end
        end
      end
    end
  end

  class Base
    mattr_accessor :warn_on_result_set_size, instance_writer: false
    self.warn_on_result_set_size = nil
  end

  Relation.prepend Relation::WarnOnResultSetSize
end