Class: Delayed::Backend::ActiveRecord::Job

Inherits:
AbstractJob show all
Includes:
Base
Defined in:
lib/delayed/backend/active_record.rb

Overview

A job object that is persisted to the database. Contains the work object as a YAML field.

Direct Known Subclasses

Failed

Defined Under Namespace

Classes: Failed

Constant Summary

Constants included from Base

Base::ON_HOLD_BLOCKER, Base::ON_HOLD_COUNT, Base::ON_HOLD_LOCKED_BY

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Base

#batch?, #expired?, #failed?, #full_name, #hold!, included, #inferred_max_attempts, #initialize_defaults, #invoke_job, #locked?, #name, #on_hold?, #payload_object, #payload_object=, #permanent_failure, #reschedule, #reschedule_at, #unhold!, #unlock

Methods inherited from ActiveRecord::Base

#encode_with, load_for_delayed_job

Instance Attribute Details

#enqueue_result ⇒ Object

Returns the value of attribute enqueue_result.



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# File 'lib/delayed/backend/active_record.rb', line 28

def enqueue_result
  @enqueue_result
end

Class Method Details

.advisory_lock(lock_name) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 54

def advisory_lock(lock_name)
  fn_name = connection.quote_table_name("half_md5_as_bigint")
  lock_name = connection.quote_string(lock_name)
  connection.execute("SELECT pg_advisory_xact_lock(#{fn_name}('#{lock_name}'));")
end

.all_available(queue = Delayed::Settings.queue, min_priority = nil, max_priority = nil, forced_latency: nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 492

def self.all_available(queue = Delayed::Settings.queue,
                       min_priority = nil,
                       max_priority = nil,
                       forced_latency: nil)
  min_priority ||= Delayed::MIN_PRIORITY
  max_priority ||= Delayed::MAX_PRIORITY

  check_queue(queue)
  check_priorities(min_priority, max_priority)

  ready_to_run(forced_latency: forced_latency)
    .where(priority: min_priority..max_priority, queue: queue)
    .by_priority
end

.apply_temp_strand!(job_scope, max_concurrent: 1) ⇒ Object

given a scope of non-stranded queued jobs, apply a temporary strand to throttle their execution returns [job_count, new_strand] (this is designed for use in a Rails console or the Canvas Jobs interface)



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# File 'lib/delayed/backend/active_record.rb', line 341

def self.apply_temp_strand!(job_scope, max_concurrent: 1)
  if job_scope.where("strand IS NOT NULL OR singleton IS NOT NULL").exists?
    raise ArgumentError, "can't apply strand to already stranded jobs"
  end

  job_count = 0
  new_strand = "tmp_strand_#{SecureRandom.alphanumeric(16)}"
  ::Delayed::Job.transaction do
    job_count = job_scope.update_all(strand: new_strand, max_concurrent: max_concurrent, next_in_strand: false)
    ::Delayed::Job.where(strand: new_strand).order(:id).limit(max_concurrent).update_all(next_in_strand: true)
  end

  [job_count, new_strand]
end

.attempt_advisory_lock(lock_name) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 48

def attempt_advisory_lock(lock_name)
  fn_name = connection.quote_table_name("half_md5_as_bigint")
  lock_name = connection.quote_string(lock_name)
  connection.select_value("SELECT pg_try_advisory_xact_lock(#{fn_name}('#{lock_name}'));")
end

.bulk_update(action, opts) ⇒ Object

perform a bulk update of a set of jobs action is :hold, :unhold, or :destroy to specify the jobs to act on, either pass opts = [list of job ids] or opts = <some flavor> to perform on all jobs of that flavor



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# File 'lib/delayed/backend/active_record.rb', line 287

def self.bulk_update(action, opts)
  raise("Can't #{action} failed jobs") if opts[:flavor].to_s == "failed" && action.to_s != "destroy"

  scope = if opts[:ids]
            if opts[:flavor] == "failed"
              Delayed::Job::Failed.where(id: opts[:ids])
            else
              where(id: opts[:ids])
            end
          elsif opts[:flavor]

            scope_for_flavor(opts[:flavor], opts[:query])
          end

  return 0 unless scope

  case action.to_s
  when "hold"
    scope = scope.where(locked_by: nil)
    scope.update_all(locked_by: ON_HOLD_LOCKED_BY, locked_at: db_time_now, attempts: ON_HOLD_COUNT)
  when "unhold"
    now = db_time_now
    scope = scope.where(locked_by: ON_HOLD_LOCKED_BY)
    scope.update_all([<<~SQL.squish, now, now])
      locked_by=NULL, locked_at=NULL, attempts=0, run_at=(CASE WHEN run_at > ? THEN run_at ELSE ? END), failed_at=NULL
    SQL
  when "destroy"
    scope = scope.where("locked_by IS NULL OR locked_by=?", ON_HOLD_LOCKED_BY) unless opts[:flavor] == "failed"
    scope.delete_all
  end
end

.by_priority ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 218

def self.by_priority
  order(:priority, :run_at, :id)
end

.clear_locks!(worker_name) ⇒ Object

When a worker is exiting, make sure we don’t have any locked jobs.



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# File 'lib/delayed/backend/active_record.rb', line 223

def self.clear_locks!(worker_name)
  where(locked_by: worker_name).update_all(locked_by: nil, locked_at: nil)
end

.create(attributes, &block) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 41

def create(attributes, &block)
  on_conflict = attributes.delete(:on_conflict)
  # modified from ActiveRecord::Persistence.create and ActiveRecord::Persistence#_insert_record
  job = new(attributes, &block)
  job.single_step_create(on_conflict: on_conflict)
end

.create_singleton(options) ⇒ Object

Create the job on the specified strand, but only if there aren’t any other non-running jobs on that strand. (in other words, the job will still be created if there’s another job on the strand but it’s already running)



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# File 'lib/delayed/backend/active_record.rb', line 511

def self.create_singleton(options)
  strand = options[:singleton]
  on_conflict = options.delete(:on_conflict) || :use_earliest

  transaction_for_singleton(singleton, on_conflict) do
    job = where(strand: strand, locked_at: nil).next_in_strand_order.first
    new_job = new(options)
    if job
      new_job.initialize_defaults
      job.run_at =
        case on_conflict
        when :use_earliest, :patient
          [job.run_at, new_job.run_at].min
        when :overwrite
          new_job.run_at
        when :loose
          job.run_at
        end
      job.handler = new_job.handler if on_conflict == :overwrite
      job.save! if job.changed?
    else
      new_job.save!
    end
    job || new_job
  end
end

.current ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 189

def self.current
  where("run_at<=?", db_time_now)
end

.failed ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 197

def self.failed
  where.not(failed_at: nil)
end

.find_available(limit, queue = Delayed::Settings.queue, min_priority = nil, max_priority = nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 485

def self.find_available(limit,
                        queue = Delayed::Settings.queue,
                        min_priority = nil,
                        max_priority = nil)
  all_available(queue, min_priority, max_priority).limit(limit).to_a
end

.future ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 193

def self.future
  where("run_at>?", db_time_now)
end

.get_and_lock_next_available(worker_names, queue = Delayed::Settings.queue, min_priority = nil, max_priority = nil, prefetch: 0, prefetch_owner: nil, forced_latency: nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 364

def self.get_and_lock_next_available(worker_names,
                                     queue = Delayed::Settings.queue,
                                     min_priority = nil,
                                     max_priority = nil,
                                     prefetch: 0,
                                     prefetch_owner: nil,
                                     forced_latency: nil)

  check_queue(queue)
  check_priorities(min_priority, max_priority)

  loop do
    jobs = maybe_silence_periodic_log do
      if connection.adapter_name == "PostgreSQL" && !Settings.select_random_from_batch
        # In Postgres, we can lock a job and return which row was locked in a single
        # query by using RETURNING. Combine that with the ROW_NUMBER() window function
        # to assign a distinct locked_at value to each job locked, when doing multiple
        # jobs in a single query.
        effective_worker_names = Array(worker_names)

        lock = nil
        lock = "FOR UPDATE SKIP LOCKED" if connection.postgresql_version >= 90_500
        target_jobs = all_available(queue,
                                    min_priority,
                                    max_priority,
                                    forced_latency: forced_latency)
                      .limit(effective_worker_names.length + prefetch)
                      .lock(lock)
        jobs_with_row_number = all.from(target_jobs)
                                  .select("id, ROW_NUMBER() OVER () AS row_number")
        updates = +"locked_by = CASE row_number "
        effective_worker_names.each_with_index do |worker, i|
          updates << "WHEN #{i + 1} THEN #{connection.quote(worker)} "
        end
        updates << "ELSE #{connection.quote(prefetch_owner)} " if prefetch_owner
        updates << "END, locked_at = #{connection.quote(db_time_now)}"

        # Originally this was done with a subquery, but this allows the query planner to
        # side-step the LIMIT. We use a CTE here to force the subquery to be materialized
        # before running the UPDATE.
        #
        # For more details, see:
        #  * https://dba.stackexchange.com/a/69497/55285
        #  * https://github.com/feikesteenbergen/demos/blob/b7ecee8b2a79bf04cbcd74972e6bfb81903aee5d/bugs/update_limit_bug.txt
        query = <<~SQL.squish
          WITH limited_jobs AS (#{jobs_with_row_number.to_sql})
          UPDATE #{quoted_table_name} SET #{updates} FROM limited_jobs WHERE limited_jobs.id=#{quoted_table_name}.id
          RETURNING #{quoted_table_name}.*
        SQL

        begin
          jobs = find_by_sql(query)
        rescue ::ActiveRecord::RecordNotUnique => e
          # if we got a unique violation on a singleton, it's because next_in_strand
          # somehow got set to true on the non-running job when there is a running
          # job. AFAICT this is not possible from inst-jobs itself, but has happened
          # in production - either due to manual manipulation of jobs, or possibly
          # a process in something like switchman-inst-jobs
          raise unless e.message.include?('"index_delayed_jobs_on_singleton_running"')

          # just repair the "strand"
          singleton = e.message.match(/Key \(singleton\)=\((.+)\) already exists.$/)[1]
          raise unless singleton

          transaction do
            # very conservatively lock the locked job, so that it won't unlock from underneath us and
            # leave an orphaned strand
            advisory_lock("singleton:#{singleton}")
            locked_jobs = where(singleton: singleton).where.not(locked_by: nil).lock.pluck(:id)
            # if it's already gone, then we're good and should be able to just retry
            if locked_jobs.length == 1
              updated = where(singleton: singleton, next_in_strand: true)
                        .where(locked_by: nil)
                        .update_all(next_in_strand: false)
              raise if updated.zero?
            end
          end

          retry
        end
        # because this is an atomic query, we don't have to return more jobs than we needed
        # to try and lock them, nor is there a possibility we need to try again because
        # all of the jobs we tried to lock had already been locked by someone else
        return jobs.first unless worker_names.is_a?(Array)

        result = jobs.index_by(&:locked_by)
        # all of the prefetched jobs can come back as an array
        result[prefetch_owner] = jobs.select { |j| j.locked_by == prefetch_owner } if prefetch_owner
        return result
      else
        batch_size = Settings.fetch_batch_size
        batch_size *= worker_names.length if worker_names.is_a?(Array)
        find_available(batch_size, queue, min_priority, max_priority)
      end
    end
    if jobs.empty?
      return worker_names.is_a?(Array) ? {} : nil
    end

    jobs = jobs.sort_by { rand } if Settings.select_random_from_batch
    if worker_names.is_a?(Array)
      result = {}
      jobs.each do |job|
        break if worker_names.empty?

        worker_name = worker_names.first
        if job.send(:lock_exclusively!, worker_name)
          result[worker_name] = job
          worker_names.shift
        end
      end
      return result
    else
      locked_job = jobs.detect do |job|
        job.send(:lock_exclusively!, worker_names)
      end
      return locked_job if locked_job
    end
  end
end

.jobs_count(flavor, query = nil) ⇒ Object

get the total job count for the given flavor see list_jobs for documentation on arguments



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# File 'lib/delayed/backend/active_record.rb', line 277

def self.jobs_count(flavor,
                    query = nil)
  scope = scope_for_flavor(flavor, query)
  scope.count
end

.list_jobs(flavor, limit, offset = 0, query = nil) ⇒ Object

get a list of jobs of the given flavor in the given queue flavor is :current, :future, :failed, :strand or :tag depending on the flavor, query has a different meaning: for :current and :future, it’s the queue name (defaults to Delayed::Settings.queue) for :strand it’s the strand name for :tag it’s the tag name for :failed it’s ignored



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# File 'lib/delayed/backend/active_record.rb', line 266

def self.list_jobs(flavor,
                   limit,
                   offset = 0,
                   query = nil)
  scope = scope_for_flavor(flavor, query)
  order = (flavor.to_s == "future") ? "run_at" : "id desc"
  scope.order(order).limit(limit).offset(offset).to_a
end

.maybe_silence_periodic_log(&block) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 356

def self.maybe_silence_periodic_log(&block)
  if Settings.silence_periodic_log
    ::ActiveRecord::Base.logger.silence(&block)
  else
    yield
  end
end

.n_strand_options(strand_name, num_strands) ⇒ Object

This overwrites the previous behavior so rather than changing the strand and balancing at queue time, this keeps the strand intact and uses triggers to limit the number running



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# File 'lib/delayed/backend/active_record.rb', line 185

def self.n_strand_options(strand_name, num_strands)
  { strand: strand_name, max_concurrent: num_strands }
end

.prefetch_jobs_lock_name ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 543

def self.prefetch_jobs_lock_name
  "Delayed::Job.unlock_orphaned_prefetched_jobs"
end

.processes_locked_locally(name: nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 538

def self.processes_locked_locally(name: nil)
  name ||= Socket.gethostname rescue x
  where("locked_by LIKE ?", "#{name}:%").pluck(:locked_by).map { |locked_by| locked_by.split(":").last.to_i }
end

.ready_to_run(forced_latency: nil) ⇒ Object

a nice stress test: 10_000.times do |i|

Kernel.delay(strand: 's1', run_at: (24.hours.ago + (rand(24.hours.to_i))).system("echo #{i} >> test1.txt")

end 500.times { |i| “ohai”.delay(run_at: (12.hours.ago + (rand(24.hours.to_i))).reverse } then fire up your workers you can check out strand correctness: diff test1.txt <(sort -n test1.txt)



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# File 'lib/delayed/backend/active_record.rb', line 212

def self.ready_to_run(forced_latency: nil)
  now = db_time_now
  now -= forced_latency if forced_latency
  where("run_at<=? AND locked_at IS NULL AND next_in_strand=?", now, true)
end

.reconnect! ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 32

def self.reconnect!
  if Rails.version < "6.1"
    ::ActiveRecord::Base.connection_handler.clear_all_connections!
  else
    ::ActiveRecord::Base.connection_handler.clear_all_connections!(nil)
  end
end

.running ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 201

def self.running
  where("locked_at IS NOT NULL AND locked_by<>'on hold'")
end

.running_jobs ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 231

def self.running_jobs
  running.order(:locked_at)
end

.scope_for_flavor(flavor, query) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 235

def self.scope_for_flavor(flavor, query)
  scope = case flavor.to_s
          when "current"
            current
          when "future"
            future
          when "failed"
            Delayed::Job::Failed
          when "strand"
            where(strand: query)
          when "tag"
            where(tag: query)
          else
            raise ArgumentError, "invalid flavor: #{flavor.inspect}"
          end

  if %w[current future].include?(flavor.to_s)
    queue = query.presence || Delayed::Settings.queue
    scope = scope.where(queue: queue)
  end

  scope
end

.strand_size(strand) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 227

def self.strand_size(strand)
  where(strand: strand).count
end

.tag_counts(flavor, limit, offset = 0) ⇒ Object

returns a list of hashes { :tag => tag_name, :count => current_count } in descending count order flavor is :current or :all

Raises:

  • (ArgumentError) 


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# File 'lib/delayed/backend/active_record.rb', line 322

def self.tag_counts(flavor,
                    limit,
                    offset = 0)
  raise(ArgumentError, "invalid flavor: #{flavor}") unless %w[current all].include?(flavor.to_s)

  scope = case flavor.to_s
          when "current"
            current
          when "all"
            self
          end

  scope = scope.group(:tag).offset(offset).limit(limit)
  scope.order(Arel.sql("COUNT(tag) DESC")).count.map { |t, c| { tag: t, count: c } }
end

.unlock(jobs) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 558

def self.unlock(jobs)
  unlocked = where(id: jobs).update_all(locked_at: nil, locked_by: nil)
  jobs.each(&:unlock)
  unlocked
end

.unlock_orphaned_prefetched_jobs ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 547

def self.unlock_orphaned_prefetched_jobs
  transaction do
    # for db performance reasons, we only need one process doing this at a time
    # so if we can't get an advisory lock, just abort. we'll try again soon
    next unless attempt_advisory_lock(prefetch_jobs_lock_name)

    horizon = db_time_now - (Settings.parent_process[:prefetched_jobs_timeout] * 4)
    where("locked_by LIKE 'prefetch:%' AND locked_at<?", horizon).update_all(locked_at: nil, locked_by: nil)
  end
end

Instance Method Details

#create_and_lock!(worker) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 610

def create_and_lock!(worker)
  raise "job already exists" unless new_record?

  # we don't want to process unique constraint violations of
  # running singleton jobs; always do it as two steps
  if singleton
    single_step_create
    lock_exclusively!(worker)
    return
  end

  self.locked_at = Delayed::Job.db_time_now
  self.locked_by = worker
  single_step_create
end

#destroy ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 153

def destroy
  # skip transaction and callbacks
  destroy_row
end

#fail! ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 626

def fail!
  attrs = attributes
  attrs["original_job_id"] = attrs.delete("id") if Failed.columns_hash.key?("original_job_id")
  attrs["failed_at"] ||= self.class.db_time_now
  attrs.delete("next_in_strand")
  attrs.delete("max_concurrent")
  self.class.transaction do
    failed_job = Failed.create(attrs)
    destroy
    failed_job
  end
rescue
  # we got an error while failing the job -- we need to at least get
  # the job out of the queue
  destroy
  # re-raise so the worker logs the error, at least
  raise
end

#lock_strand_on_create ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 174

def lock_strand_on_create
  return unless strand.present? && instance_of?(Job)

  fn_name = self.class.connection.quote_table_name("half_md5_as_bigint")
  quoted_strand_name = self.class.connection.quote(strand)
  self.class.connection.execute("SELECT pg_advisory_xact_lock(#{fn_name}(#{quoted_strand_name}))")
end

#single_step_create(on_conflict: nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 61

def single_step_create(on_conflict: nil)
  connection = self.class.connection

  # a before_save callback that we're skipping
  initialize_defaults

  current_time = current_time_from_proper_timezone

  all_timestamp_attributes_in_model.each do |column|
    _write_attribute(column, current_time) unless attribute_present?(column)
  end

  attribute_names = if Rails.version < "7.0"
                      attribute_names_for_partial_writes
                    else
                      attribute_names_for_partial_inserts
                    end
  attribute_names = attributes_for_create(attribute_names)
  values = attributes_with_values(attribute_names)

  im = if Rails.version < "7.0"
         self.class.arel_table.compile_insert(self.class.send(:_substitute_values, values))
       else
         im = Arel::InsertManager.new(self.class.arel_table)
         im.insert(values.transform_keys { |name| self.class.arel_table[name] })
         im
       end

  lock_and_insert = values["strand"] && instance_of?(Job)
  # can't use prepared statements if we're combining multiple statemenets
  sql, binds = if lock_and_insert
                 connection.unprepared_statement do
                   connection.send(:to_sql_and_binds, im)
                 end
               else
                 connection.send(:to_sql_and_binds, im)
               end
  sql = +sql

  if singleton && instance_of?(Job)
    sql << " ON CONFLICT (singleton) WHERE singleton IS NOT NULL AND locked_by IS NULL DO "
    sql << case on_conflict
           when :patient, :loose
             "NOTHING"
           when :overwrite
             "UPDATE SET run_at=EXCLUDED.run_at, handler=EXCLUDED.handler"
           else # :use_earliest
             "UPDATE SET run_at=EXCLUDED.run_at WHERE EXCLUDED.run_at<delayed_jobs.run_at"
           end
  end

  # https://www.postgresql.org/docs/9.5/libpq-exec.html
  # https://stackoverflow.com/questions/39058213/differentiate-inserted-and-updated-rows-in-upsert-using-system-columns
  sql << " RETURNING id, (xmax = 0) AS inserted"

  if lock_and_insert
    # > Multiple queries sent in a single PQexec call are processed in a single transaction,
    # unless there are explicit BEGIN/COMMIT commands included in the query string to divide
    # it into multiple transactions.
    # but we don't need to lock when inserting into Delayed::Failed
    if values["strand"] && instance_of?(Job)
      fn_name = connection.quote_table_name("half_md5_as_bigint")
      quoted_strand = connection.quote((Rails.version < "7.0") ? values["strand"] : values["strand"].value)
      sql = "SELECT pg_advisory_xact_lock(#{fn_name}(#{quoted_strand})); #{sql}"
    end
    result = connection.execute(sql, "#{self.class} Create")
    self.id = result.values.first&.first
    inserted = result.values.first&.second
    result.clear
  else
    result = connection.exec_query(sql, "#{self.class} Create", binds)
    self.id = connection.send(:last_inserted_id, result)
    inserted = result.rows.first&.second
  end

  self.enqueue_result = if id.present? && inserted
                          :inserted
                        elsif id.present? && !inserted
                          :updated
                        else
                          :dropped
                        end

  # it might not get set if there was an existing record, and we didn't update it
  if id
    @new_record = false
    changes_applied
  end

  self
end

#transfer_lock!(from:, to:) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 584

def transfer_lock!(from:, to:)
  now = self.class.db_time_now
  # We don't own this job so we will update the locked_by name and the locked_at
  affected_rows = self.class.where(id: self, locked_by: from).update_all(locked_at: now, locked_by: to)
  if affected_rows == 1
    mark_as_locked!(now, to)
    true
  else
    false
  end
end