Remove dependency on IgnorableColumn concern

`IgnorableColumn` module in `app/models/concerns/ignorable_column.rb`
which is used in models to ignore dealing with specified columns.

In Rails 5 with this [pull
request](https://github.com/rails/rails/pull/21720),
`self.ignored_columns` was introduced to do this job.

For example, in app/models/user.rb:

```ruby
ignore_column :external_email
ignore_column :email_provider
```

can be changed to:

```ruby
self.ignored_columns = %i[external_email email_provider]
```

app/models/application_setting.rb

@@ -4,7 +4,6 @@ class ApplicationSetting < ApplicationRecord
   include CacheableAttributes
   include CacheMarkdownField
   include TokenAuthenticatable
-  include IgnorableColumn
   include ChronicDurationAttribute
 
   add_authentication_token_field :runners_registration_token, encrypted: -> { Feature.enabled?(:application_settings_tokens_optional_encryption, default_enabled: true) ? :optional : :required }
@@ -32,12 +31,14 @@ class ApplicationSetting < ApplicationRecord
   serialize :repository_storages # rubocop:disable Cop/ActiveRecordSerialize
   serialize :asset_proxy_whitelist, Array # rubocop:disable Cop/ActiveRecordSerialize
 
-  ignore_column :koding_url
-  ignore_column :koding_enabled
-  ignore_column :sentry_enabled
-  ignore_column :sentry_dsn
-  ignore_column :clientside_sentry_enabled
-  ignore_column :clientside_sentry_dsn
+  self.ignored_columns = %i[
+                         clientside_sentry_dsn
+                         clientside_sentry_enabled
+                         koding_enabled
+                         koding_url
+                         sentry_dsn
+                         sentry_enabled
+                         ]
 
   cache_markdown_field :sign_in_text
   cache_markdown_field :help_page_text

app/models/ci/build.rb

@@ -11,19 +11,20 @@ module Ci
     include ObjectStorage::BackgroundMove
     include Presentable
     include Importable
-    include IgnorableColumn
     include Gitlab::Utils::StrongMemoize
     include Deployable
     include HasRef
 
     BuildArchivedError = Class.new(StandardError)
 
-    ignore_column :commands
-    ignore_column :artifacts_file
-    ignore_column :artifacts_metadata
-    ignore_column :artifacts_file_store
-    ignore_column :artifacts_metadata_store
-    ignore_column :artifacts_size
+    self.ignored_columns = %i[
+                           artifacts_file
+                           artifacts_file_store
+                           artifacts_metadata
+                           artifacts_metadata_store
+                           artifacts_size
+                           commands
+                           ]
 
     belongs_to :project, inverse_of: :builds
     belongs_to :runner

app/models/ci/runner.rb

@@ -4,7 +4,6 @@ module Ci
   class Runner < ApplicationRecord
     extend Gitlab::Ci::Model
     include Gitlab::SQL::Pattern
-    include IgnorableColumn
     include RedisCacheable
     include ChronicDurationAttribute
     include FromUnion
@@ -36,7 +35,7 @@ module Ci
 
     FORM_EDITABLE = %i[description tag_list active run_untagged locked access_level maximum_timeout_human_readable].freeze
 
-    ignore_column :is_shared
+    self.ignored_columns = %i[is_shared]
 
     has_many :builds
     has_many :runner_projects, inverse_of: :runner, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent

app/models/concerns/ignorable_column.rb

-# frozen_string_literal: true
-
-# Module that can be included into a model to make it easier to ignore database
-# columns.
-#
-# Example:
-#
-#     class User < ApplicationRecord
-#       include IgnorableColumn
-#
-#       ignore_column :updated_at
-#     end
-#
-module IgnorableColumn
-  extend ActiveSupport::Concern
-
-  class_methods do
-    def columns
-      super.reject { |column| ignored_columns.include?(column.name) }
-    end
-
-    def ignored_columns
-      @ignored_columns ||= Set.new
-    end
-
-    def ignore_column(*names)
-      ignored_columns.merge(names.map(&:to_s))
-    end
-  end
-end

app/models/deploy_key.rb

 # frozen_string_literal: true
 
 class DeployKey < Key
-  include IgnorableColumn
   include FromUnion
 
   has_many :deploy_keys_projects, inverse_of: :deploy_key, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
@@ -11,7 +10,7 @@ class DeployKey < Key
   scope :are_public,  -> { where(public: true) }
   scope :with_projects, -> { includes(deploy_keys_projects: { project: [:route, :namespace] }) }
 
-  ignore_column :can_push
+  self.ignored_columns = %i[can_push]
 
   accepts_nested_attributes_for :deploy_keys_projects
 

app/models/event.rb

@@ -2,7 +2,6 @@
 
 class Event < ApplicationRecord
   include Sortable
-  include IgnorableColumn
   include FromUnion
   default_scope { reorder(nil) }
 

app/models/merge_request_diff.rb

@@ -4,7 +4,6 @@ class MergeRequestDiff < ApplicationRecord
   include Sortable
   include Importable
   include ManualInverseAssociation
-  include IgnorableColumn
   include EachBatch
   include Gitlab::Utils::StrongMemoize
   include ObjectStorage::BackgroundMove

app/models/note.rb

@@ -14,7 +14,6 @@ class Note < ApplicationRecord
   include CacheMarkdownField
   include AfterCommitQueue
   include ResolvableNote
-  include IgnorableColumn
   include Editable
   include Gitlab::SQL::Pattern
   include ThrottledTouch
@@ -34,7 +33,7 @@ class Note < ApplicationRecord
     end
   end
 
-  ignore_column :original_discussion_id
+  self.ignored_columns = %i[original_discussion_id]
 
   cache_markdown_field :note, pipeline: :note, issuable_state_filter_enabled: true
 

app/models/notification_setting.rb

 # frozen_string_literal: true
 
 class NotificationSetting < ApplicationRecord
-  include IgnorableColumn
-
-  ignore_column :events
+  self.ignored_columns = %i[events]
 
   enum level: { global: 3, watch: 2, participating: 1, mention: 4, disabled: 0, custom: 5 }
 

app/models/user.rb

@@ -13,7 +13,6 @@ class User < ApplicationRecord
   include Sortable
   include CaseSensitivity
   include TokenAuthenticatable
-  include IgnorableColumn
   include FeatureGate
   include CreatedAtFilterable
   include BulkMemberAccessLoad
@@ -24,9 +23,11 @@ class User < ApplicationRecord
 
   DEFAULT_NOTIFICATION_LEVEL = :participating
 
-  ignore_column :external_email
-  ignore_column :email_provider
-  ignore_column :authentication_token
+  self.ignored_columns = %i[
+                         authentication_token
+                         email_provider
+                         external_email
+                         ]
 
   add_authentication_token_field :incoming_email_token, token_generator: -> { SecureRandom.hex.to_i(16).to_s(36) }
   add_authentication_token_field :feed_token

doc/development/what_requires_downtime.md

@@ -45,15 +45,12 @@ rule.
 
 The first step is to ignore the column in the application code. This is
 necessary because Rails caches the columns and re-uses this cache in various
-places. This can be done by including the `IgnorableColumn` module into the
-model, followed by defining the columns to ignore. For example, to ignore
+places. This can be done by defining the columns to ignore. For example, to ignore
 `updated_at` in the User model you'd use the following:
 
 ```ruby
-class User < ActiveRecord::Base
-  include IgnorableColumn
-
-  ignore_column :updated_at
+class User < ApplicationRecord
+  self.ignored_columns = %i[updated_at]
 end
 ```
 
@@ -64,8 +61,7 @@ column. Both these changes should be submitted in the same merge request.
 
 Once the changes from step 1 have been released & deployed you can set up a
 separate merge request that removes the ignore rule. This merge request can
-simply remove the `ignore_column` line, and the `include IgnorableColumn` line
-if no other `ignore_column` calls remain.
+simply remove the `self.ignored_columns` line.
 
 ## Renaming Columns
 

ee/app/models/ee/application_setting.rb

@@ -9,14 +9,12 @@ module EE
     extend ActiveSupport::Concern
 
     prepended do
-      include IgnorableColumn
-
       EMAIL_ADDITIONAL_TEXT_CHARACTER_LIMIT = 10_000
       INSTANCE_REVIEW_MIN_USERS = 100
 
       belongs_to :file_template_project, class_name: "Project"
 
-      ignore_column :minimum_mirror_sync_time
+      self.ignored_columns = %i[minimum_mirror_sync_time]
 
       validates :shared_runners_minutes,
                 numericality: { greater_than_or_equal_to: 0 }

ee/app/models/ee/project.rb

@@ -19,12 +19,13 @@ module EE
       include EE::DeploymentPlatform # rubocop: disable Cop/InjectEnterpriseEditionModule
       include EachBatch
       include InsightsFeature
-      include IgnorableColumn
       include Vulnerable
 
-      ignore_column :mirror_last_update_at,
-        :mirror_last_successful_update_at,
-        :next_execution_timestamp
+      self.ignored_columns = %i[
+        mirror_last_update_at
+        mirror_last_successful_update_at
+        next_execution_timestamp
+      ]
 
       before_save :set_override_pull_mirror_available, unless: -> { ::Gitlab::CurrentSettings.mirror_available }
       before_save :set_next_execution_timestamp_to_now, if: ->(project) { project.mirror? && project.mirror_changed? && project.import_state }

ee/app/models/ee/project_import_state.rb

@@ -6,8 +6,7 @@ module EE
     extend ::Gitlab::Utils::Override
 
     prepended do
-      include IgnorableColumn
-      ignore_column :created_at, :updated_at
+      self.ignored_columns = %i[created_at updated_at]
 
       BACKOFF_PERIOD = 24.seconds
       JITTER = 6.seconds

ee/app/models/ee/user.rb

@@ -18,7 +18,7 @@ module EE
     prepended do
       EMAIL_OPT_IN_SOURCE_ID_GITLAB_COM = 1
 
-      ignore_column :support_bot
+      self.ignored_columns = %i[support_bot]
 
       # We aren't using the `auditor?` method for the `if` condition here
       # because `auditor?` returns `false` when the `auditor` column is `true`

ee/app/models/project_repository_state.rb

 # frozen_string_literal: true
 
 class ProjectRepositoryState < ApplicationRecord
-  include IgnorableColumn
   include ShaAttribute
 
-  ignore_column :last_repository_verification_failed
-  ignore_column :last_wiki_verification_failed
+  self.ignored_columns = %i[last_repository_verification_failed last_wiki_verification_failed]
 
   sha_attribute :repository_verification_checksum
   sha_attribute :wiki_verification_checksum

spec/models/concerns/ignorable_column_spec.rb

-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe IgnorableColumn do
-  let :base_class do
-    Class.new do
-      def self.columns
-        # This method does not have access to "double"
-        [
-          Struct.new(:name).new('id'),
-          Struct.new(:name).new('title'),
-          Struct.new(:name).new('date')
-        ]
-      end
-    end
-  end
-
-  let :model do
-    Class.new(base_class) do
-      include IgnorableColumn
-    end
-  end
-
-  describe '.columns' do
-    it 'returns the columns, excluding the ignored ones' do
-      model.ignore_column(:title, :date)
-
-      expect(model.columns.map(&:name)).to eq(%w(id))
-    end
-  end
-
-  describe '.ignored_columns' do
-    it 'returns a Set' do
-      expect(model.ignored_columns).to be_an_instance_of(Set)
-    end
-
-    it 'returns the names of the ignored columns' do
-      model.ignore_column(:title, :date)
-
-      expect(model.ignored_columns).to eq(Set.new(%w(title date)))
-    end
-  end
-end