Remove background migrations for old schemas

On the assumption that a background migration whose specs need a schema
older than 2018 is obsoleted by this migration squash, we can remove
both specs and code for those that fail to run in CI as a result of the
schema at that date no longer existing.

This is true for all but the MigrateStageStatus background migration,
which is also used from the MigrateBuildStage background migration.

6 files changed, 0 insertions, 757 deletions

diff --git a/lib/gitlab/background_migration/create_fork_network_memberships_range.rb b/lib/gitlab/background_migration/create_fork_network_memberships_range.rb
deleted file mode 100644
index ccd1f9b4dba..00000000000
--- a/lib/gitlab/background_migration/create_fork_network_memberships_range.rb
+++ /dev/null
@@ -1,85 +0,0 @@
-# frozen_string_literal: true
-# rubocop:disable Style/Documentation
-
-module Gitlab
-  module BackgroundMigration
-    class CreateForkNetworkMembershipsRange
-      RESCHEDULE_DELAY = 15
-
-      class ForkedProjectLink < ActiveRecord::Base
-        self.table_name = 'forked_project_links'
-      end
-
-      def perform(start_id, end_id)
-        log("Creating memberships for forks: #{start_id} - #{end_id}")
-
-        insert_members(start_id, end_id)
-
-        if missing_members?(start_id, end_id)
-          BackgroundMigrationWorker.perform_in(RESCHEDULE_DELAY, "CreateForkNetworkMembershipsRange", [start_id, end_id])
-        end
-      end
-
-      def insert_members(start_id, end_id)
-        ActiveRecord::Base.connection.execute <<~INSERT_MEMBERS
-          INSERT INTO fork_network_members (fork_network_id, project_id, forked_from_project_id)
-
-          SELECT fork_network_members.fork_network_id,
-                 forked_project_links.forked_to_project_id,
-                 forked_project_links.forked_from_project_id
-
-          FROM forked_project_links
-
-          INNER JOIN fork_network_members
-              ON forked_project_links.forked_from_project_id = fork_network_members.project_id
-
-          WHERE forked_project_links.id BETWEEN #{start_id} AND #{end_id}
-          AND NOT EXISTS (
-            SELECT true
-            FROM fork_network_members existing_members
-            WHERE existing_members.project_id = forked_project_links.forked_to_project_id
-          )
-        INSERT_MEMBERS
-      rescue ActiveRecord::RecordNotUnique => e
-        # `fork_network_member` was created concurrently in another migration
-        log(e.message)
-      end
-
-      def missing_members?(start_id, end_id)
-        count_sql = <<~MISSING_MEMBERS
-          SELECT COUNT(*)
-
-          FROM forked_project_links
-
-          WHERE NOT EXISTS (
-            SELECT true
-            FROM fork_network_members
-            WHERE fork_network_members.project_id = forked_project_links.forked_to_project_id
-          )
-          AND EXISTS (
-            SELECT true
-            FROM projects
-            WHERE forked_project_links.forked_from_project_id = projects.id
-          )
-          AND NOT EXISTS (
-            SELECT true
-            FROM forked_project_links AS parent_links
-            WHERE parent_links.forked_to_project_id = forked_project_links.forked_from_project_id
-            AND NOT EXISTS (
-              SELECT true
-              FROM projects
-              WHERE parent_links.forked_from_project_id = projects.id
-            )
-          )
-          AND forked_project_links.id BETWEEN #{start_id} AND #{end_id}
-        MISSING_MEMBERS
-
-        ForkedProjectLink.count_by_sql(count_sql) > 0
-      end
-
-      def log(message)
-        Rails.logger.info("#{self.class.name} - #{message}")
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb b/lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb
deleted file mode 100644
index 21b626dde56..00000000000
--- a/lib/gitlab/background_migration/delete_conflicting_redirect_routes_range.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-# frozen_string_literal: true
-# rubocop:disable Style/Documentation
-
-module Gitlab
-  module BackgroundMigration
-    class DeleteConflictingRedirectRoutesRange
-      def perform(start_id, end_id)
-        # No-op.
-        # See https://gitlab.com/gitlab-com/infrastructure/issues/3460#note_53223252
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb b/lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb
deleted file mode 100644
index 42fcaa87e66..00000000000
--- a/lib/gitlab/background_migration/migrate_events_to_push_event_payloads.rb
+++ /dev/null
@@ -1,179 +0,0 @@
-# frozen_string_literal: true
-# rubocop:disable Style/Documentation
-
-module Gitlab
-  module BackgroundMigration
-    # Class that migrates events for the new push event payloads setup. All
-    # events are copied to a shadow table, and push events will also have a row
-    # created in the push_event_payloads table.
-    class MigrateEventsToPushEventPayloads
-      class Event < ActiveRecord::Base
-        self.table_name = 'events'
-
-        serialize :data
-
-        BLANK_REF = ('0' * 40).freeze
-        TAG_REF_PREFIX = 'refs/tags/'.freeze
-        MAX_INDEX = 69
-        PUSHED = 5
-
-        def push_event?
-          action == PUSHED && data.present?
-        end
-
-        def commit_title
-          commit = commits.last
-
-          return unless commit && commit[:message]
-
-          index = commit[:message].index("\n")
-          message = index ? commit[:message][0..index] : commit[:message]
-
-          message.strip.truncate(70)
-        end
-
-        def commit_from_sha
-          if create?
-            nil
-          else
-            data[:before]
-          end
-        end
-
-        def commit_to_sha
-          if remove?
-            nil
-          else
-            data[:after]
-          end
-        end
-
-        def data
-          super || {}
-        end
-
-        def commits
-          data[:commits] || []
-        end
-
-        def commit_count
-          data[:total_commits_count] || 0
-        end
-
-        def ref
-          data[:ref]
-        end
-
-        def trimmed_ref_name
-          if ref_type == :tag
-            ref[10..-1]
-          else
-            ref[11..-1]
-          end
-        end
-
-        def create?
-          data[:before] == BLANK_REF
-        end
-
-        def remove?
-          data[:after] == BLANK_REF
-        end
-
-        def push_action
-          if create?
-            :created
-          elsif remove?
-            :removed
-          else
-            :pushed
-          end
-        end
-
-        def ref_type
-          if ref.start_with?(TAG_REF_PREFIX)
-            :tag
-          else
-            :branch
-          end
-        end
-      end
-
-      class EventForMigration < ActiveRecord::Base
-        self.table_name = 'events_for_migration'
-      end
-
-      class PushEventPayload < ActiveRecord::Base
-        self.table_name = 'push_event_payloads'
-
-        enum action: {
-          created: 0,
-          removed: 1,
-          pushed: 2
-        }
-
-        enum ref_type: {
-          branch: 0,
-          tag: 1
-        }
-      end
-
-      # start_id - The start ID of the range of events to process
-      # end_id - The end ID of the range to process.
-      def perform(start_id, end_id)
-        return unless migrate?
-
-        find_events(start_id, end_id).each { |event| process_event(event) }
-      end
-
-      def process_event(event)
-        ActiveRecord::Base.transaction do
-          replicate_event(event)
-          create_push_event_payload(event) if event.push_event?
-        end
-      rescue ActiveRecord::InvalidForeignKey => e
-        # A foreign key error means the associated event was removed. In this
-        # case we'll just skip migrating the event.
-        Rails.logger.error("Unable to migrate event #{event.id}: #{e}")
-      end
-
-      def replicate_event(event)
-        new_attributes = event.attributes
-          .with_indifferent_access.except(:title, :data)
-
-        EventForMigration.create!(new_attributes)
-      end
-
-      def create_push_event_payload(event)
-        commit_from = pack(event.commit_from_sha)
-        commit_to = pack(event.commit_to_sha)
-
-        PushEventPayload.create!(
-          event_id: event.id,
-          commit_count: event.commit_count,
-          ref_type: event.ref_type,
-          action: event.push_action,
-          commit_from: commit_from,
-          commit_to: commit_to,
-          ref: event.trimmed_ref_name,
-          commit_title: event.commit_title
-        )
-      end
-
-      def find_events(start_id, end_id)
-        Event
-          .where('NOT EXISTS (SELECT true FROM events_for_migration WHERE events_for_migration.id = events.id)')
-          .where(id: start_id..end_id)
-      end
-
-      def migrate?
-        Event.table_exists? && PushEventPayload.table_exists? &&
-          EventForMigration.table_exists?
-      end
-
-      def pack(value)
-        value ? [value].pack('H*') : nil
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb b/lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb
deleted file mode 100644
index 48aa369705f..00000000000
--- a/lib/gitlab/background_migration/normalize_ldap_extern_uids_range.rb
+++ /dev/null
@@ -1,319 +0,0 @@
-# frozen_string_literal: true
-# rubocop:disable Metrics/MethodLength
-# rubocop:disable Metrics/ClassLength
-# rubocop:disable Metrics/BlockLength
-# rubocop:disable Style/Documentation
-
-module Gitlab
-  module BackgroundMigration
-    class NormalizeLdapExternUidsRange
-      class Identity < ActiveRecord::Base
-        self.table_name = 'identities'
-      end
-
-      # Copied this class to make this migration resilient to future code changes.
-      # And if the normalize behavior is changed in the future, it must be
-      # accompanied by another migration.
-      module Gitlab
-        module Auth
-          module LDAP
-            class DN
-              FormatError = Class.new(StandardError)
-              MalformedError = Class.new(FormatError)
-              UnsupportedError = Class.new(FormatError)
-
-              def self.normalize_value(given_value)
-                dummy_dn = "placeholder=#{given_value}"
-                normalized_dn = new(*dummy_dn).to_normalized_s
-                normalized_dn.sub(/\Aplaceholder=/, '')
-              end
-
-              ##
-              # Initialize a DN, escaping as required. Pass in attributes in name/value
-              # pairs. If there is a left over argument, it will be appended to the dn
-              # without escaping (useful for a base string).
-              #
-              # Most uses of this class will be to escape a DN, rather than to parse it,
-              # so storing the dn as an escaped String and parsing parts as required
-              # with a state machine seems sensible.
-              def initialize(*args)
-                if args.length > 1
-                  initialize_array(args)
-                else
-                  initialize_string(args[0])
-                end
-              end
-
-              ##
-              # Parse a DN into key value pairs using ASN from
-              # http://tools.ietf.org/html/rfc2253 section 3.
-              # rubocop:disable Metrics/AbcSize
-              # rubocop:disable Metrics/CyclomaticComplexity
-              # rubocop:disable Metrics/PerceivedComplexity
-              def each_pair
-                state = :key
-                key = StringIO.new
-                value = StringIO.new
-                hex_buffer = ""
-
-                @dn.each_char.with_index do |char, dn_index|
-                  case state
-                  when :key then
-                    case char
-                    when 'a'..'z', 'A'..'Z' then
-                      state = :key_normal
-                      key << char
-                    when '0'..'9' then
-                      state = :key_oid
-                      key << char
-                    when ' ' then state = :key
-                    else raise(MalformedError, "Unrecognized first character of an RDN attribute type name \"#{char}\"")
-                    end
-                  when :key_normal then
-                    case char
-                    when '=' then state = :value
-                    when 'a'..'z', 'A'..'Z', '0'..'9', '-', ' ' then key << char
-                    else raise(MalformedError, "Unrecognized RDN attribute type name character \"#{char}\"")
-                    end
-                  when :key_oid then
-                    case char
-                    when '=' then state = :value
-                    when '0'..'9', '.', ' ' then key << char
-                    else raise(MalformedError, "Unrecognized RDN OID attribute type name character \"#{char}\"")
-                    end
-                  when :value then
-                    case char
-                    when '\\' then state = :value_normal_escape
-                    when '"' then state = :value_quoted
-                    when ' ' then state = :value
-                    when '#' then
-                      state = :value_hexstring
-                      value << char
-                    when ',' then
-                      state = :key
-                      yield key.string.strip, rstrip_except_escaped(value.string, dn_index)
-                      key = StringIO.new
-                      value = StringIO.new
-                    else
-                      state = :value_normal
-                      value << char
-                    end
-                  when :value_normal then
-                    case char
-                    when '\\' then state = :value_normal_escape
-                    when ',' then
-                      state = :key
-                      yield key.string.strip, rstrip_except_escaped(value.string, dn_index)
-                      key = StringIO.new
-                      value = StringIO.new
-                    when '+' then raise(UnsupportedError, "Multivalued RDNs are not supported")
-                    else value << char
-                    end
-                  when :value_normal_escape then
-                    case char
-                    when '0'..'9', 'a'..'f', 'A'..'F' then
-                      state = :value_normal_escape_hex
-                      hex_buffer = char
-                    else
-                      state = :value_normal
-                      value << char
-                    end
-                  when :value_normal_escape_hex then
-                    case char
-                    when '0'..'9', 'a'..'f', 'A'..'F' then
-                      state = :value_normal
-                      value << "#{hex_buffer}#{char}".to_i(16).chr
-                    else raise(MalformedError, "Invalid escaped hex code \"\\#{hex_buffer}#{char}\"")
-                    end
-                  when :value_quoted then
-                    case char
-                    when '\\' then state = :value_quoted_escape
-                    when '"' then state = :value_end
-                    else value << char
-                    end
-                  when :value_quoted_escape then
-                    case char
-                    when '0'..'9', 'a'..'f', 'A'..'F' then
-                      state = :value_quoted_escape_hex
-                      hex_buffer = char
-                    else
-                      state = :value_quoted
-                      value << char
-                    end
-                  when :value_quoted_escape_hex then
-                    case char
-                    when '0'..'9', 'a'..'f', 'A'..'F' then
-                      state = :value_quoted
-                      value << "#{hex_buffer}#{char}".to_i(16).chr
-                    else raise(MalformedError, "Expected the second character of a hex pair inside a double quoted value, but got \"#{char}\"")
-                    end
-                  when :value_hexstring then
-                    case char
-                    when '0'..'9', 'a'..'f', 'A'..'F' then
-                      state = :value_hexstring_hex
-                      value << char
-                    when ' ' then state = :value_end
-                    when ',' then
-                      state = :key
-                      yield key.string.strip, rstrip_except_escaped(value.string, dn_index)
-                      key = StringIO.new
-                      value = StringIO.new
-                    else raise(MalformedError, "Expected the first character of a hex pair, but got \"#{char}\"")
-                    end
-                  when :value_hexstring_hex then
-                    case char
-                    when '0'..'9', 'a'..'f', 'A'..'F' then
-                      state = :value_hexstring
-                      value << char
-                    else raise(MalformedError, "Expected the second character of a hex pair, but got \"#{char}\"")
-                    end
-                  when :value_end then
-                    case char
-                    when ' ' then state = :value_end
-                    when ',' then
-                      state = :key
-                      yield key.string.strip, rstrip_except_escaped(value.string, dn_index)
-                      key = StringIO.new
-                      value = StringIO.new
-                    else raise(MalformedError, "Expected the end of an attribute value, but got \"#{char}\"")
-                    end
-                  else raise "Fell out of state machine"
-                  end
-                end
-
-                # Last pair
-                raise(MalformedError, 'DN string ended unexpectedly') unless
-                  [:value, :value_normal, :value_hexstring, :value_end].include? state
-
-                yield key.string.strip, rstrip_except_escaped(value.string, @dn.length)
-              end
-
-              def rstrip_except_escaped(str, dn_index)
-                str_ends_with_whitespace = str.match(/\s\z/)
-
-                if str_ends_with_whitespace
-                  dn_part_ends_with_escaped_whitespace = @dn[0, dn_index].match(/\\(\s+)\z/)
-
-                  if dn_part_ends_with_escaped_whitespace
-                    dn_part_rwhitespace = dn_part_ends_with_escaped_whitespace[1]
-                    num_chars_to_remove = dn_part_rwhitespace.length - 1
-                    str = str[0, str.length - num_chars_to_remove]
-                  else
-                    str.rstrip!
-                  end
-                end
-
-                str
-              end
-
-              ##
-              # Returns the DN as an array in the form expected by the constructor.
-              def to_a
-                a = []
-                self.each_pair { |key, value| a << key << value } unless @dn.empty?
-                a
-              end
-
-              ##
-              # Return the DN as an escaped string.
-              def to_s
-                @dn
-              end
-
-              ##
-              # Return the DN as an escaped and normalized string.
-              def to_normalized_s
-                self.class.new(*to_a).to_s.downcase
-              end
-
-              # https://tools.ietf.org/html/rfc4514 section 2.4 lists these exceptions
-              # for DN values. All of the following must be escaped in any normal string
-              # using a single backslash ('\') as escape. The space character is left
-              # out here because in a "normalized" string, spaces should only be escaped
-              # if necessary (i.e. leading or trailing space).
-              NORMAL_ESCAPES = [',', '+', '"', '\\', '<', '>', ';', '='].freeze
-
-              # The following must be represented as escaped hex
-              HEX_ESCAPES = {
-                "\n" => '\0a',
-                "\r" => '\0d'
-              }.freeze
-
-              # Compiled character class regexp using the keys from the above hash, and
-              # checking for a space or # at the start, or space at the end, of the
-              # string.
-              ESCAPE_RE = Regexp.new("(^ |^#| $|[" +
-                                    NORMAL_ESCAPES.map { |e| Regexp.escape(e) }.join +
-                                    "])")
-
-              HEX_ESCAPE_RE = Regexp.new("([" +
-                                    HEX_ESCAPES.keys.map { |e| Regexp.escape(e) }.join +
-                                    "])")
-
-              ##
-              # Escape a string for use in a DN value
-              def self.escape(string)
-                escaped = string.gsub(ESCAPE_RE) { |char| "\\" + char }
-                escaped.gsub(HEX_ESCAPE_RE) { |char| HEX_ESCAPES[char] }
-              end
-
-              private
-
-              def initialize_array(args)
-                buffer = StringIO.new
-
-                args.each_with_index do |arg, index|
-                  if index.even? # key
-                    buffer << "," if index > 0
-                    buffer << arg
-                  else # value
-                    buffer << "="
-                    buffer << self.class.escape(arg)
-                  end
-                end
-
-                @dn = buffer.string
-              end
-
-              def initialize_string(arg)
-                @dn = arg.to_s
-              end
-
-              ##
-              # Proxy all other requests to the string object, because a DN is mainly
-              # used within the library as a string
-              # rubocop:disable GitlabSecurity/PublicSend
-              def method_missing(method, *args, &block)
-                @dn.send(method, *args, &block)
-              end
-
-              ##
-              # Redefined to be consistent with redefined `method_missing` behavior
-              def respond_to?(sym, include_private = false)
-                @dn.respond_to?(sym, include_private)
-              end
-            end
-          end
-        end
-      end
-
-      def perform(start_id, end_id)
-        return unless migrate?
-
-        ldap_identities = Identity.where("provider like 'ldap%'").where(id: start_id..end_id)
-        ldap_identities.each do |identity|
-          identity.extern_uid = Gitlab::Auth::LDAP::DN.new(identity.extern_uid).to_normalized_s
-          unless identity.save
-            Rails.logger.info "Unable to normalize \"#{identity.extern_uid}\". Skipping."
-          end
-        rescue Gitlab::Auth::LDAP::DN::FormatError => e
-          Rails.logger.info "Unable to normalize \"#{identity.extern_uid}\" due to \"#{e.message}\". Skipping."
-        end
-      end
-
-      def migrate?
-        Identity.table_exists?
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/background_migration/populate_fork_networks_range.rb b/lib/gitlab/background_migration/populate_fork_networks_range.rb
deleted file mode 100644
index aa4f130538c..00000000000
--- a/lib/gitlab/background_migration/populate_fork_networks_range.rb
+++ /dev/null
@@ -1,128 +0,0 @@
-# frozen_string_literal: true
-
-module Gitlab
-  module BackgroundMigration
-    # This background migration is going to create all `fork_networks` and
-    # the `fork_network_members` for the roots of fork networks based on the
-    # existing `forked_project_links`.
-    #
-    # When the source of a fork is deleted, we will create the fork with the
-    # target project as the root. This way, when there are forks of the target
-    # project, they will be joined into the same fork network.
-    #
-    # When the `fork_networks` and memberships for the root projects are created
-    # the `CreateForkNetworkMembershipsRange` migration is scheduled. This
-    # migration will create the memberships for all remaining forks-of-forks
-    class PopulateForkNetworksRange
-      def perform(start_id, end_id)
-        create_fork_networks_for_existing_projects(start_id, end_id)
-        create_fork_networks_for_missing_projects(start_id, end_id)
-        create_fork_networks_memberships_for_root_projects(start_id, end_id)
-
-        delay = BackgroundMigration::CreateForkNetworkMembershipsRange::RESCHEDULE_DELAY
-        BackgroundMigrationWorker.perform_in(
-          delay, "CreateForkNetworkMembershipsRange", [start_id, end_id]
-        )
-      end
-
-      def create_fork_networks_for_existing_projects(start_id, end_id)
-        log("Creating fork networks: #{start_id} - #{end_id}")
-        ActiveRecord::Base.connection.execute <<~INSERT_NETWORKS
-        INSERT INTO fork_networks (root_project_id)
-          SELECT DISTINCT forked_project_links.forked_from_project_id
-
-          FROM forked_project_links
-
-          -- Exclude the forks that are not the first level fork of a project
-          WHERE NOT EXISTS (
-            SELECT true
-            FROM forked_project_links inner_links
-            WHERE inner_links.forked_to_project_id = forked_project_links.forked_from_project_id
-          )
-
-          /* Exclude the ones that are already created, in case the fork network
-             was already created for another fork of the project.
-          */
-          AND NOT EXISTS (
-            SELECT true
-            FROM fork_networks
-            WHERE forked_project_links.forked_from_project_id = fork_networks.root_project_id
-          )
-
-          -- Only create a fork network for a root project that still exists
-          AND EXISTS (
-            SELECT true
-            FROM projects
-            WHERE projects.id = forked_project_links.forked_from_project_id
-          )
-          AND forked_project_links.id BETWEEN #{start_id} AND #{end_id}
-        INSERT_NETWORKS
-      end
-
-      def create_fork_networks_for_missing_projects(start_id, end_id)
-        log("Creating fork networks with missing root: #{start_id} - #{end_id}")
-        ActiveRecord::Base.connection.execute <<~INSERT_NETWORKS
-        INSERT INTO fork_networks (root_project_id)
-          SELECT DISTINCT forked_project_links.forked_to_project_id
-
-          FROM forked_project_links
-
-          -- Exclude forks that are not the root forks
-          WHERE NOT EXISTS (
-            SELECT true
-            FROM forked_project_links inner_links
-            WHERE inner_links.forked_to_project_id = forked_project_links.forked_from_project_id
-          )
-
-          /* Exclude the ones that are already created, in case this migration is
-             re-run
-          */
-          AND NOT EXISTS (
-            SELECT true
-            FROM fork_networks
-            WHERE forked_project_links.forked_to_project_id = fork_networks.root_project_id
-          )
-
-          /* Exclude projects for which the project still exists, those are
-             Processed in the previous step of this migration
-          */
-          AND NOT EXISTS (
-            SELECT true
-            FROM projects
-            WHERE projects.id = forked_project_links.forked_from_project_id
-          )
-          AND forked_project_links.id BETWEEN #{start_id} AND #{end_id}
-        INSERT_NETWORKS
-      end
-
-      def create_fork_networks_memberships_for_root_projects(start_id, end_id)
-        log("Creating memberships for root projects: #{start_id} - #{end_id}")
-
-        ActiveRecord::Base.connection.execute <<~INSERT_ROOT
-          INSERT INTO fork_network_members (fork_network_id, project_id)
-          SELECT DISTINCT fork_networks.id, fork_networks.root_project_id
-
-          FROM fork_networks
-
-          /* Joining both on forked_from- and forked_to- so we could create the
-             memberships for forks for which the source was deleted
-          */
-          INNER JOIN forked_project_links
-              ON forked_project_links.forked_from_project_id = fork_networks.root_project_id
-              OR forked_project_links.forked_to_project_id = fork_networks.root_project_id
-
-          WHERE NOT EXISTS (
-            SELECT true
-            FROM fork_network_members
-            WHERE fork_network_members.project_id = fork_networks.root_project_id
-          )
-          AND forked_project_links.id BETWEEN #{start_id} AND #{end_id}
-        INSERT_ROOT
-      end
-
-      def log(message)
-        Rails.logger.info("#{self.class.name} - #{message}")
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb b/lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb
deleted file mode 100644
index dcac355e1b0..00000000000
--- a/lib/gitlab/background_migration/populate_merge_requests_latest_merge_request_diff_id.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-# frozen_string_literal: true
-# rubocop:disable Style/Documentation
-
-module Gitlab
-  module BackgroundMigration
-    class PopulateMergeRequestsLatestMergeRequestDiffId
-      BATCH_SIZE = 1_000
-
-      class MergeRequest < ActiveRecord::Base
-        self.table_name = 'merge_requests'
-
-        include ::EachBatch
-      end
-
-      def perform(start_id, stop_id)
-        update = '
-          latest_merge_request_diff_id = (
-            SELECT MAX(id)
-            FROM merge_request_diffs
-            WHERE merge_requests.id = merge_request_diffs.merge_request_id
-          )'.squish
-
-        MergeRequest
-          .where(id: start_id..stop_id)
-          .where(latest_merge_request_diff_id: nil)
-          .each_batch(of: BATCH_SIZE) do |relation|
-
-          relation.update_all(update)
-        end
-      end
-    end
-  end
-end