about summary refs log tree commit diff
diff options
context:
space:
mode:
-rw-r--r--app/models/account_domain_block.rb4
-rw-r--r--app/models/block.rb6
-rw-r--r--app/models/conversation_mute.rb4
-rw-r--r--app/models/domain_block.rb2
-rw-r--r--app/models/favourite.rb6
-rw-r--r--app/models/follow.rb6
-rw-r--r--app/models/follow_request.rb6
-rw-r--r--app/models/import.rb4
-rw-r--r--app/models/mention.rb4
-rw-r--r--app/models/mute.rb6
-rw-r--r--app/models/report.rb6
-rw-r--r--app/models/setting.rb4
-rw-r--r--app/models/stream_entry.rb5
-rw-r--r--app/models/subscription.rb4
-rw-r--r--app/models/web/setting.rb4
-rw-r--r--db/migrate/20170918125918_ids_to_bigints.rb232
-rw-r--r--db/schema.rb134
-rw-r--r--lib/mastodon/migration_helpers.rb988
18 files changed, 1202 insertions, 223 deletions
diff --git a/app/models/account_domain_block.rb b/app/models/account_domain_block.rb
index bdd64c01a..fb695e473 100644
--- a/app/models/account_domain_block.rb
+++ b/app/models/account_domain_block.rb
@@ -3,11 +3,11 @@
 #
 # Table name: account_domain_blocks
 #
-#  id         :integer          not null, primary key
-#  account_id :integer
 #  domain     :string
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
+#  account_id :integer
+#  id         :integer          not null, primary key
 #
 
 class AccountDomainBlock < ApplicationRecord
diff --git a/app/models/block.rb b/app/models/block.rb
index edb0d2d11..a913782ed 100644
--- a/app/models/block.rb
+++ b/app/models/block.rb
@@ -3,11 +3,11 @@
 #
 # Table name: blocks
 #
-#  id                :integer          not null, primary key
-#  account_id        :integer          not null
-#  target_account_id :integer          not null
 #  created_at        :datetime         not null
 #  updated_at        :datetime         not null
+#  account_id        :integer          not null
+#  id                :integer          not null, primary key
+#  target_account_id :integer          not null
 #
 
 class Block < ApplicationRecord
diff --git a/app/models/conversation_mute.rb b/app/models/conversation_mute.rb
index 79299b995..8d2399adf 100644
--- a/app/models/conversation_mute.rb
+++ b/app/models/conversation_mute.rb
@@ -3,9 +3,9 @@
 #
 # Table name: conversation_mutes
 #
-#  id              :integer          not null, primary key
-#  account_id      :integer          not null
 #  conversation_id :integer          not null
+#  account_id      :integer          not null
+#  id              :integer          not null, primary key
 #
 
 class ConversationMute < ApplicationRecord
diff --git a/app/models/domain_block.rb b/app/models/domain_block.rb
index aea8919af..1268290bc 100644
--- a/app/models/domain_block.rb
+++ b/app/models/domain_block.rb
@@ -3,12 +3,12 @@
 #
 # Table name: domain_blocks
 #
-#  id           :integer          not null, primary key
 #  domain       :string           default(""), not null
 #  created_at   :datetime         not null
 #  updated_at   :datetime         not null
 #  severity     :integer          default("silence")
 #  reject_media :boolean          default(FALSE), not null
+#  id           :integer          not null, primary key
 #
 
 class DomainBlock < ApplicationRecord
diff --git a/app/models/favourite.rb b/app/models/favourite.rb
index 53c79ccea..d28d5c05b 100644
--- a/app/models/favourite.rb
+++ b/app/models/favourite.rb
@@ -3,11 +3,11 @@
 #
 # Table name: favourites
 #
-#  id         :integer          not null, primary key
-#  account_id :integer          not null
-#  status_id  :integer          not null
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
+#  account_id :integer          not null
+#  id         :integer          not null, primary key
+#  status_id  :integer          not null
 #
 
 class Favourite < ApplicationRecord
diff --git a/app/models/follow.rb b/app/models/follow.rb
index 62f6fb670..667720a88 100644
--- a/app/models/follow.rb
+++ b/app/models/follow.rb
@@ -3,11 +3,11 @@
 #
 # Table name: follows
 #
-#  id                :integer          not null, primary key
-#  account_id        :integer          not null
-#  target_account_id :integer          not null
 #  created_at        :datetime         not null
 #  updated_at        :datetime         not null
+#  account_id        :integer          not null
+#  id                :integer          not null, primary key
+#  target_account_id :integer          not null
 #
 
 class Follow < ApplicationRecord
diff --git a/app/models/follow_request.rb b/app/models/follow_request.rb
index 458c3a2cd..60036d903 100644
--- a/app/models/follow_request.rb
+++ b/app/models/follow_request.rb
@@ -3,11 +3,11 @@
 #
 # Table name: follow_requests
 #
-#  id                :integer          not null, primary key
-#  account_id        :integer          not null
-#  target_account_id :integer          not null
 #  created_at        :datetime         not null
 #  updated_at        :datetime         not null
+#  account_id        :integer          not null
+#  id                :integer          not null, primary key
+#  target_account_id :integer          not null
 #
 
 class FollowRequest < ApplicationRecord
diff --git a/app/models/import.rb b/app/models/import.rb
index 4656c3af6..8ae7e3a46 100644
--- a/app/models/import.rb
+++ b/app/models/import.rb
@@ -3,8 +3,6 @@
 #
 # Table name: imports
 #
-#  id                :integer          not null, primary key
-#  account_id        :integer          not null
 #  type              :integer          not null
 #  approved          :boolean          default(FALSE), not null
 #  created_at        :datetime         not null
@@ -13,6 +11,8 @@
 #  data_content_type :string
 #  data_file_size    :integer
 #  data_updated_at   :datetime
+#  account_id        :integer          not null
+#  id                :integer          not null, primary key
 #
 
 class Import < ApplicationRecord
diff --git a/app/models/mention.rb b/app/models/mention.rb
index 7450b1b85..3700c781c 100644
--- a/app/models/mention.rb
+++ b/app/models/mention.rb
@@ -3,11 +3,11 @@
 #
 # Table name: mentions
 #
-#  id         :integer          not null, primary key
-#  account_id :integer
 #  status_id  :integer
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
+#  account_id :integer
+#  id         :integer          not null, primary key
 #
 
 class Mention < ApplicationRecord
diff --git a/app/models/mute.rb b/app/models/mute.rb
index 00e5661a7..6e64848c7 100644
--- a/app/models/mute.rb
+++ b/app/models/mute.rb
@@ -3,11 +3,11 @@
 #
 # Table name: mutes
 #
-#  id                :integer          not null, primary key
-#  account_id        :integer          not null
-#  target_account_id :integer          not null
 #  created_at        :datetime         not null
 #  updated_at        :datetime         not null
+#  account_id        :integer          not null
+#  id                :integer          not null, primary key
+#  target_account_id :integer          not null
 #
 
 class Mute < ApplicationRecord
diff --git a/app/models/report.rb b/app/models/report.rb
index 479aa17bb..bffb42b48 100644
--- a/app/models/report.rb
+++ b/app/models/report.rb
@@ -3,15 +3,15 @@
 #
 # Table name: reports
 #
-#  id                         :integer          not null, primary key
-#  account_id                 :integer          not null
-#  target_account_id          :integer          not null
 #  status_ids                 :integer          default([]), not null, is an Array
 #  comment                    :text             default(""), not null
 #  action_taken               :boolean          default(FALSE), not null
 #  created_at                 :datetime         not null
 #  updated_at                 :datetime         not null
+#  account_id                 :integer          not null
 #  action_taken_by_account_id :integer
+#  id                         :integer          not null, primary key
+#  target_account_id          :integer          not null
 #
 
 class Report < ApplicationRecord
diff --git a/app/models/setting.rb b/app/models/setting.rb
index 340552581..a14f156a1 100644
--- a/app/models/setting.rb
+++ b/app/models/setting.rb
@@ -3,13 +3,13 @@
 #
 # Table name: settings
 #
-#  id         :integer          not null, primary key
 #  var        :string           not null
 #  value      :text
 #  thing_type :string
-#  thing_id   :integer
 #  created_at :datetime
 #  updated_at :datetime
+#  id         :integer          not null, primary key
+#  thing_id   :integer
 #
 
 class Setting < RailsSettings::Base
diff --git a/app/models/stream_entry.rb b/app/models/stream_entry.rb
index 44aac39b3..b51fe9ad7 100644
--- a/app/models/stream_entry.rb
+++ b/app/models/stream_entry.rb
@@ -1,16 +1,15 @@
 # frozen_string_literal: true
-
 # == Schema Information
 #
 # Table name: stream_entries
 #
-#  id            :integer          not null, primary key
-#  account_id    :integer
 #  activity_id   :integer
 #  activity_type :string
 #  created_at    :datetime         not null
 #  updated_at    :datetime         not null
 #  hidden        :boolean          default(FALSE), not null
+#  account_id    :integer
+#  id            :integer          not null, primary key
 #
 
 class StreamEntry < ApplicationRecord
diff --git a/app/models/subscription.rb b/app/models/subscription.rb
index 14f1a140c..39860196b 100644
--- a/app/models/subscription.rb
+++ b/app/models/subscription.rb
@@ -3,16 +3,16 @@
 #
 # Table name: subscriptions
 #
-#  id                          :integer          not null, primary key
 #  callback_url                :string           default(""), not null
 #  secret                      :string
 #  expires_at                  :datetime
 #  confirmed                   :boolean          default(FALSE), not null
-#  account_id                  :integer          not null
 #  created_at                  :datetime         not null
 #  updated_at                  :datetime         not null
 #  last_successful_delivery_at :datetime
 #  domain                      :string
+#  account_id                  :integer          not null
+#  id                          :integer          not null, primary key
 #
 
 class Subscription < ApplicationRecord
diff --git a/app/models/web/setting.rb b/app/models/web/setting.rb
index 04a049523..1b0bfb2b7 100644
--- a/app/models/web/setting.rb
+++ b/app/models/web/setting.rb
@@ -3,11 +3,11 @@
 #
 # Table name: web_settings
 #
-#  id         :integer          not null, primary key
-#  user_id    :integer
 #  data       :json
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
+#  id         :integer          not null, primary key
+#  user_id    :integer
 #
 
 class Web::Setting < ApplicationRecord
diff --git a/db/migrate/20170918125918_ids_to_bigints.rb b/db/migrate/20170918125918_ids_to_bigints.rb
index 7483dd77a..c6feed8f9 100644
--- a/db/migrate/20170918125918_ids_to_bigints.rb
+++ b/db/migrate/20170918125918_ids_to_bigints.rb
@@ -1,127 +1,119 @@
+require Rails.root.join('lib', 'mastodon', 'migration_helpers')
+
 class IdsToBigints < ActiveRecord::Migration[5.1]
+  include Mastodon::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  INCLUDED_COLUMNS = [
+    [:account_domain_blocks, :account_id],
+    [:account_domain_blocks, :id],
+    [:accounts, :id],
+    [:blocks, :account_id],
+    [:blocks, :id],
+    [:blocks, :target_account_id],
+    [:conversation_mutes, :account_id],
+    [:conversation_mutes, :id],
+    [:domain_blocks, :id],
+    [:favourites, :account_id],
+    [:favourites, :id],
+    [:favourites, :status_id],
+    [:follow_requests, :account_id],
+    [:follow_requests, :id],
+    [:follow_requests, :target_account_id],
+    [:follows, :account_id],
+    [:follows, :id],
+    [:follows, :target_account_id],
+    [:imports, :account_id],
+    [:imports, :id],
+    [:media_attachments, :account_id],
+    [:media_attachments, :id],
+    [:mentions, :account_id],
+    [:mentions, :id],
+    [:mutes, :account_id],
+    [:mutes, :id],
+    [:mutes, :target_account_id],
+    [:notifications, :account_id],
+    [:notifications, :from_account_id],
+    [:notifications, :id],
+    [:oauth_access_grants, :application_id],
+    [:oauth_access_grants, :id],
+    [:oauth_access_grants, :resource_owner_id],
+    [:oauth_access_tokens, :application_id],
+    [:oauth_access_tokens, :id],
+    [:oauth_access_tokens, :resource_owner_id],
+    [:oauth_applications, :id],
+    [:oauth_applications, :owner_id],
+    [:reports, :account_id],
+    [:reports, :action_taken_by_account_id],
+    [:reports, :id],
+    [:reports, :target_account_id],
+    [:session_activations, :access_token_id],
+    [:session_activations, :user_id],
+    [:session_activations, :web_push_subscription_id],
+    [:settings, :id],
+    [:settings, :thing_id],
+    [:statuses, :account_id],
+    [:statuses, :application_id],
+    [:statuses, :in_reply_to_account_id],
+    [:stream_entries, :account_id],
+    [:stream_entries, :id],
+    [:subscriptions, :account_id],
+    [:subscriptions, :id],
+    [:tags, :id],
+    [:users, :account_id],
+    [:users, :id],
+    [:web_settings, :id],
+    [:web_settings, :user_id],
+  ]
+  INCLUDED_COLUMNS << [:deprecated_preview_cards, :id] if table_exists?(:deprecated_preview_cards)
+
+  def migrate_columns(to_type)
+    # Print out a warning that this will probably take a while.
+    say ''
+    say 'WARNING: This migration may take a *long* time for large instances'
+    say 'It will *not* lock tables for any significant time, but it may run'
+    say 'for a very long time. We will pause for 10 seconds to allow you to'
+    say 'interrupt this migration if you are not ready.'
+    say ''
+    say 'This migration has some sections that can be safely interrupted'
+    say 'and restarted later, and will tell you when those are occurring.'
+    say ''
+    say 'For more information, see https://github.com/tootsuite/mastodon/pull/5088'
+
+    10.downto(1) do |i|
+      say "Continuing in #{i} second#{i == 1 ? '' : 's'}...", true
+      sleep 1
+    end
+
+    tables = INCLUDED_COLUMNS.map(&:first).uniq
+    table_sizes = {}
+
+    # Sort tables by their size
+    tables.each do |table|
+      table_sizes[table] = estimate_rows_in_table(table)
+    end
+
+    ordered_columns = INCLUDED_COLUMNS.sort_by do |col_parts|
+      [-table_sizes[col_parts.first], col_parts.last]
+    end
+
+    ordered_columns.each do |column_parts|
+      table, column = column_parts
+
+      # Skip this if we're resuming and already did this one.
+      next if column_for(table, column).sql_type == to_type.to_s
+
+      change_column_type_concurrently table, column, to_type
+      cleanup_concurrent_column_type_change table, column
+    end
+  end
+
   def up
-    change_column :account_domain_blocks, :account_id, :bigint
-    change_column :account_domain_blocks, :id, :bigint
-    change_column :accounts, :id, :bigint
-    change_column :blocks, :account_id, :bigint
-    change_column :blocks, :id, :bigint
-    change_column :blocks, :target_account_id, :bigint
-    change_column :conversation_mutes, :account_id, :bigint
-    change_column :conversation_mutes, :id, :bigint
-    change_column :deprecated_preview_cards, :id, :bigint if table_exists?(:deprecated_preview_cards)
-    change_column :domain_blocks, :id, :bigint
-    change_column :favourites, :account_id, :bigint
-    change_column :favourites, :id, :bigint
-    change_column :favourites, :status_id, :bigint
-    change_column :follow_requests, :account_id, :bigint
-    change_column :follow_requests, :id, :bigint
-    change_column :follow_requests, :target_account_id, :bigint
-    change_column :follows, :account_id, :bigint
-    change_column :follows, :id, :bigint
-    change_column :follows, :target_account_id, :bigint
-    change_column :imports, :account_id, :bigint
-    change_column :imports, :id, :bigint
-    change_column :media_attachments, :account_id, :bigint
-    change_column :media_attachments, :id, :bigint
-    change_column :mentions, :account_id, :bigint
-    change_column :mentions, :id, :bigint
-    change_column :mutes, :account_id, :bigint
-    change_column :mutes, :id, :bigint
-    change_column :mutes, :target_account_id, :bigint
-    change_column :notifications, :account_id, :bigint
-    change_column :notifications, :from_account_id, :bigint
-    change_column :notifications, :id, :bigint
-    change_column :oauth_access_grants, :application_id, :bigint
-    change_column :oauth_access_grants, :id, :bigint
-    change_column :oauth_access_grants, :resource_owner_id, :bigint
-    change_column :oauth_access_tokens, :application_id, :bigint
-    change_column :oauth_access_tokens, :id, :bigint
-    change_column :oauth_access_tokens, :resource_owner_id, :bigint
-    change_column :oauth_applications, :id, :bigint
-    change_column :oauth_applications, :owner_id, :bigint
-    change_column :reports, :account_id, :bigint
-    change_column :reports, :action_taken_by_account_id, :bigint
-    change_column :reports, :id, :bigint
-    change_column :reports, :target_account_id, :bigint
-    change_column :session_activations, :access_token_id, :bigint
-    change_column :session_activations, :user_id, :bigint
-    change_column :session_activations, :web_push_subscription_id, :bigint
-    change_column :settings, :id, :bigint
-    change_column :settings, :thing_id, :bigint
-    change_column :statuses, :account_id, :bigint
-    change_column :statuses, :application_id, :bigint
-    change_column :statuses, :in_reply_to_account_id, :bigint
-    change_column :stream_entries, :account_id, :bigint
-    change_column :stream_entries, :id, :bigint
-    change_column :subscriptions, :account_id, :bigint
-    change_column :subscriptions, :id, :bigint
-    change_column :tags, :id, :bigint
-    change_column :users, :account_id, :bigint
-    change_column :users, :id, :bigint
-    change_column :web_settings, :id, :bigint
-    change_column :web_settings, :user_id, :bigint
+    migrate_columns(:bigint)
   end
 
   def down
-    change_column :account_domain_blocks, :account_id, :integer
-    change_column :account_domain_blocks, :id, :integer
-    change_column :accounts, :id, :integer
-    change_column :blocks, :account_id, :integer
-    change_column :blocks, :id, :integer
-    change_column :blocks, :target_account_id, :integer
-    change_column :conversation_mutes, :account_id, :integer
-    change_column :conversation_mutes, :id, :integer
-    change_column :deprecated_preview_cards, :id, :integer if table_exists?(:deprecated_preview_cards)
-    change_column :domain_blocks, :id, :integer
-    change_column :favourites, :account_id, :integer
-    change_column :favourites, :id, :integer
-    change_column :favourites, :status_id, :integer
-    change_column :follow_requests, :account_id, :integer
-    change_column :follow_requests, :id, :integer
-    change_column :follow_requests, :target_account_id, :integer
-    change_column :follows, :account_id, :integer
-    change_column :follows, :id, :integer
-    change_column :follows, :target_account_id, :integer
-    change_column :imports, :account_id, :integer
-    change_column :imports, :id, :integer
-    change_column :media_attachments, :account_id, :integer
-    change_column :media_attachments, :id, :integer
-    change_column :mentions, :account_id, :integer
-    change_column :mentions, :id, :integer
-    change_column :mutes, :account_id, :integer
-    change_column :mutes, :id, :integer
-    change_column :mutes, :target_account_id, :integer
-    change_column :notifications, :account_id, :integer
-    change_column :notifications, :from_account_id, :integer
-    change_column :notifications, :id, :integer
-    change_column :oauth_access_grants, :application_id, :integer
-    change_column :oauth_access_grants, :id, :integer
-    change_column :oauth_access_grants, :resource_owner_id, :integer
-    change_column :oauth_access_tokens, :application_id, :integer
-    change_column :oauth_access_tokens, :id, :integer
-    change_column :oauth_access_tokens, :resource_owner_id, :integer
-    change_column :oauth_applications, :id, :integer
-    change_column :oauth_applications, :owner_id, :integer
-    change_column :reports, :account_id, :integer
-    change_column :reports, :action_taken_by_account_id, :integer
-    change_column :reports, :id, :integer
-    change_column :reports, :target_account_id, :integer
-    change_column :session_activations, :access_token_id, :integer
-    change_column :session_activations, :user_id, :integer
-    change_column :session_activations, :web_push_subscription_id, :integer
-    change_column :settings, :id, :integer
-    change_column :settings, :thing_id, :integer
-    change_column :statuses, :account_id, :integer
-    change_column :statuses, :application_id, :integer
-    change_column :statuses, :in_reply_to_account_id, :integer
-    change_column :stream_entries, :account_id, :integer
-    change_column :stream_entries, :id, :integer
-    change_column :subscriptions, :account_id, :integer
-    change_column :subscriptions, :id, :integer
-    change_column :tags, :id, :integer
-    change_column :users, :account_id, :integer
-    change_column :users, :id, :integer
-    change_column :web_settings, :id, :integer
-    change_column :web_settings, :user_id, :integer
+    migrate_columns(:integer)
   end
 end
diff --git a/db/schema.rb b/db/schema.rb
index 90f8a5683..2cb105553 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -16,10 +16,10 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   enable_extension "plpgsql"
 
   create_table "account_domain_blocks", force: :cascade do |t|
-    t.bigint "account_id"
     t.string "domain"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id"
     t.index ["account_id", "domain"], name: "index_account_domain_blocks_on_account_id_and_domain", unique: true
   end
 
@@ -69,16 +69,16 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   end
 
   create_table "blocks", force: :cascade do |t|
-    t.bigint "account_id", null: false
-    t.bigint "target_account_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id", null: false
+    t.bigint "target_account_id", null: false
     t.index ["account_id", "target_account_id"], name: "index_blocks_on_account_id_and_target_account_id", unique: true
   end
 
   create_table "conversation_mutes", force: :cascade do |t|
-    t.bigint "account_id", null: false
     t.bigint "conversation_id", null: false
+    t.bigint "account_id", null: false
     t.index ["account_id", "conversation_id"], name: "index_conversation_mutes_on_account_id_and_conversation_id", unique: true
   end
 
@@ -111,33 +111,32 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   end
 
   create_table "favourites", force: :cascade do |t|
-    t.bigint "account_id", null: false
-    t.bigint "status_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id", null: false
+    t.bigint "status_id", null: false
     t.index ["account_id", "id"], name: "index_favourites_on_account_id_and_id"
     t.index ["account_id", "status_id"], name: "index_favourites_on_account_id_and_status_id", unique: true
     t.index ["status_id"], name: "index_favourites_on_status_id"
   end
 
   create_table "follow_requests", force: :cascade do |t|
-    t.bigint "account_id", null: false
-    t.bigint "target_account_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id", null: false
+    t.bigint "target_account_id", null: false
     t.index ["account_id", "target_account_id"], name: "index_follow_requests_on_account_id_and_target_account_id", unique: true
   end
 
   create_table "follows", force: :cascade do |t|
-    t.bigint "account_id", null: false
-    t.bigint "target_account_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id", null: false
+    t.bigint "target_account_id", null: false
     t.index ["account_id", "target_account_id"], name: "index_follows_on_account_id_and_target_account_id", unique: true
   end
 
   create_table "imports", force: :cascade do |t|
-    t.bigint "account_id", null: false
     t.integer "type", null: false
     t.boolean "approved", default: false, null: false
     t.datetime "created_at", null: false
@@ -146,6 +145,7 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.string "data_content_type"
     t.integer "data_file_size"
     t.datetime "data_updated_at"
+    t.bigint "account_id", null: false
   end
 
   create_table "media_attachments", force: :cascade do |t|
@@ -155,12 +155,12 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.integer "file_file_size"
     t.datetime "file_updated_at"
     t.string "remote_url", default: "", null: false
-    t.bigint "account_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.string "shortcode"
     t.integer "type", default: 0, null: false
     t.json "file_meta"
+    t.bigint "account_id"
     t.text "description"
     t.index ["account_id"], name: "index_media_attachments_on_account_id"
     t.index ["shortcode"], name: "index_media_attachments_on_shortcode", unique: true
@@ -168,28 +168,28 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   end
 
   create_table "mentions", force: :cascade do |t|
-    t.bigint "account_id"
     t.bigint "status_id"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id"
     t.index ["account_id", "status_id"], name: "index_mentions_on_account_id_and_status_id", unique: true
     t.index ["status_id"], name: "index_mentions_on_status_id"
   end
 
   create_table "mutes", force: :cascade do |t|
-    t.bigint "account_id", null: false
-    t.bigint "target_account_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id", null: false
+    t.bigint "target_account_id", null: false
     t.index ["account_id", "target_account_id"], name: "index_mutes_on_account_id_and_target_account_id", unique: true
   end
 
   create_table "notifications", force: :cascade do |t|
-    t.bigint "account_id"
     t.bigint "activity_id"
     t.string "activity_type"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id"
     t.bigint "from_account_id"
     t.index ["account_id", "activity_id", "activity_type"], name: "account_activity", unique: true
     t.index ["activity_id", "activity_type"], name: "index_notifications_on_activity_id_and_activity_type"
@@ -197,26 +197,26 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   end
 
   create_table "oauth_access_grants", force: :cascade do |t|
-    t.bigint "resource_owner_id", null: false
-    t.bigint "application_id", null: false
     t.string "token", null: false
     t.integer "expires_in", null: false
     t.text "redirect_uri", null: false
     t.datetime "created_at", null: false
     t.datetime "revoked_at"
     t.string "scopes"
+    t.bigint "application_id", null: false
+    t.bigint "resource_owner_id", null: false
     t.index ["token"], name: "index_oauth_access_grants_on_token", unique: true
   end
 
   create_table "oauth_access_tokens", force: :cascade do |t|
-    t.bigint "resource_owner_id"
-    t.bigint "application_id"
     t.string "token", null: false
     t.string "refresh_token"
     t.integer "expires_in"
     t.datetime "revoked_at"
     t.datetime "created_at", null: false
     t.string "scopes"
+    t.bigint "application_id"
+    t.bigint "resource_owner_id"
     t.index ["refresh_token"], name: "index_oauth_access_tokens_on_refresh_token", unique: true
     t.index ["resource_owner_id"], name: "index_oauth_access_tokens_on_resource_owner_id"
     t.index ["token"], name: "index_oauth_access_tokens_on_token", unique: true
@@ -232,8 +232,8 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.datetime "updated_at"
     t.boolean "superapp", default: false, null: false
     t.string "website"
-    t.bigint "owner_id"
     t.string "owner_type"
+    t.bigint "owner_id"
     t.index ["owner_id", "owner_type"], name: "index_oauth_applications_on_owner_id_and_owner_type"
     t.index ["uid"], name: "index_oauth_applications_on_uid", unique: true
   end
@@ -266,26 +266,26 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   end
 
   create_table "reports", force: :cascade do |t|
-    t.bigint "account_id", null: false
-    t.bigint "target_account_id", null: false
     t.bigint "status_ids", default: [], null: false, array: true
     t.text "comment", default: "", null: false
     t.boolean "action_taken", default: false, null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "account_id", null: false
     t.bigint "action_taken_by_account_id"
+    t.bigint "target_account_id", null: false
     t.index ["account_id"], name: "index_reports_on_account_id"
     t.index ["target_account_id"], name: "index_reports_on_target_account_id"
   end
 
   create_table "session_activations", force: :cascade do |t|
-    t.bigint "user_id", null: false
     t.string "session_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.string "user_agent", default: "", null: false
     t.inet "ip"
     t.bigint "access_token_id"
+    t.bigint "user_id", null: false
     t.bigint "web_push_subscription_id"
     t.index ["session_id"], name: "index_session_activations_on_session_id", unique: true
     t.index ["user_id"], name: "index_session_activations_on_user_id"
@@ -295,9 +295,9 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.string "var", null: false
     t.text "value"
     t.string "thing_type"
-    t.bigint "thing_id"
     t.datetime "created_at"
     t.datetime "updated_at"
+    t.bigint "thing_id"
     t.index ["thing_type", "thing_id", "var"], name: "index_settings_on_thing_type_and_thing_id_and_var", unique: true
   end
 
@@ -323,7 +323,6 @@ ActiveRecord::Schema.define(version: 20170927215609) do
 
   create_table "statuses", force: :cascade do |t|
     t.string "uri"
-    t.bigint "account_id", null: false
     t.text "text", default: "", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
@@ -332,8 +331,6 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.string "url"
     t.boolean "sensitive", default: false, null: false
     t.integer "visibility", default: 0, null: false
-    t.bigint "in_reply_to_account_id"
-    t.bigint "application_id"
     t.text "spoiler_text", default: "", null: false
     t.boolean "reply", default: false, null: false
     t.integer "favourites_count", default: 0, null: false
@@ -341,6 +338,9 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.string "language"
     t.bigint "conversation_id"
     t.boolean "local"
+    t.bigint "account_id", null: false
+    t.bigint "application_id"
+    t.bigint "in_reply_to_account_id"
     t.index ["account_id", "id"], name: "index_statuses_on_account_id_id"
     t.index ["conversation_id"], name: "index_statuses_on_conversation_id"
     t.index ["in_reply_to_id"], name: "index_statuses_on_in_reply_to_id"
@@ -356,12 +356,12 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   end
 
   create_table "stream_entries", force: :cascade do |t|
-    t.bigint "account_id"
     t.bigint "activity_id"
     t.string "activity_type"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.boolean "hidden", default: false, null: false
+    t.bigint "account_id"
     t.index ["account_id"], name: "index_stream_entries_on_account_id"
     t.index ["activity_id", "activity_type"], name: "index_stream_entries_on_activity_id_and_activity_type"
   end
@@ -371,11 +371,11 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.string "secret"
     t.datetime "expires_at"
     t.boolean "confirmed", default: false, null: false
-    t.bigint "account_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.datetime "last_successful_delivery_at"
     t.string "domain"
+    t.bigint "account_id", null: false
     t.index ["account_id", "callback_url"], name: "index_subscriptions_on_account_id_and_callback_url", unique: true
   end
 
@@ -389,7 +389,6 @@ ActiveRecord::Schema.define(version: 20170927215609) do
 
   create_table "users", force: :cascade do |t|
     t.string "email", default: "", null: false
-    t.bigint "account_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.string "encrypted_password", default: "", null: false
@@ -415,6 +414,7 @@ ActiveRecord::Schema.define(version: 20170927215609) do
     t.datetime "last_emailed_at"
     t.string "otp_backup_codes", array: true
     t.string "filtered_languages", default: [], null: false, array: true
+    t.bigint "account_id", null: false
     t.index ["account_id"], name: "index_users_on_account_id"
     t.index ["confirmation_token"], name: "index_users_on_confirmation_token", unique: true
     t.index ["email"], name: "index_users_on_email", unique: true
@@ -432,53 +432,53 @@ ActiveRecord::Schema.define(version: 20170927215609) do
   end
 
   create_table "web_settings", force: :cascade do |t|
-    t.bigint "user_id"
     t.json "data"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.bigint "user_id"
     t.index ["user_id"], name: "index_web_settings_on_user_id", unique: true
   end
 
-  add_foreign_key "account_domain_blocks", "accounts", on_delete: :cascade
-  add_foreign_key "blocks", "accounts", column: "target_account_id", on_delete: :cascade
-  add_foreign_key "blocks", "accounts", on_delete: :cascade
-  add_foreign_key "conversation_mutes", "accounts", on_delete: :cascade
+  add_foreign_key "account_domain_blocks", "accounts", name: "fk_206c6029bd", on_delete: :cascade
+  add_foreign_key "blocks", "accounts", column: "target_account_id", name: "fk_9571bfabc1", on_delete: :cascade
+  add_foreign_key "blocks", "accounts", name: "fk_4269e03e65", on_delete: :cascade
+  add_foreign_key "conversation_mutes", "accounts", name: "fk_225b4212bb", on_delete: :cascade
   add_foreign_key "conversation_mutes", "conversations", on_delete: :cascade
-  add_foreign_key "favourites", "accounts", on_delete: :cascade
-  add_foreign_key "favourites", "statuses", on_delete: :cascade
-  add_foreign_key "follow_requests", "accounts", column: "target_account_id", on_delete: :cascade
-  add_foreign_key "follow_requests", "accounts", on_delete: :cascade
-  add_foreign_key "follows", "accounts", column: "target_account_id", on_delete: :cascade
-  add_foreign_key "follows", "accounts", on_delete: :cascade
-  add_foreign_key "imports", "accounts", on_delete: :cascade
-  add_foreign_key "media_attachments", "accounts", on_delete: :nullify
+  add_foreign_key "favourites", "accounts", name: "fk_5eb6c2b873", on_delete: :cascade
+  add_foreign_key "favourites", "statuses", name: "fk_b0e856845e", on_delete: :cascade
+  add_foreign_key "follow_requests", "accounts", column: "target_account_id", name: "fk_9291ec025d", on_delete: :cascade
+  add_foreign_key "follow_requests", "accounts", name: "fk_76d644b0e7", on_delete: :cascade
+  add_foreign_key "follows", "accounts", column: "target_account_id", name: "fk_745ca29eac", on_delete: :cascade
+  add_foreign_key "follows", "accounts", name: "fk_32ed1b5560", on_delete: :cascade
+  add_foreign_key "imports", "accounts", name: "fk_6db1b6e408", on_delete: :cascade
+  add_foreign_key "media_attachments", "accounts", name: "fk_96dd81e81b", on_delete: :nullify
   add_foreign_key "media_attachments", "statuses", on_delete: :nullify
-  add_foreign_key "mentions", "accounts", on_delete: :cascade
+  add_foreign_key "mentions", "accounts", name: "fk_970d43f9d1", on_delete: :cascade
   add_foreign_key "mentions", "statuses", on_delete: :cascade
-  add_foreign_key "mutes", "accounts", column: "target_account_id", on_delete: :cascade
-  add_foreign_key "mutes", "accounts", on_delete: :cascade
-  add_foreign_key "notifications", "accounts", column: "from_account_id", on_delete: :cascade
-  add_foreign_key "notifications", "accounts", on_delete: :cascade
-  add_foreign_key "oauth_access_grants", "oauth_applications", column: "application_id", on_delete: :cascade
-  add_foreign_key "oauth_access_grants", "users", column: "resource_owner_id", on_delete: :cascade
-  add_foreign_key "oauth_access_tokens", "oauth_applications", column: "application_id", on_delete: :cascade
-  add_foreign_key "oauth_access_tokens", "users", column: "resource_owner_id", on_delete: :cascade
-  add_foreign_key "oauth_applications", "users", column: "owner_id", on_delete: :cascade
-  add_foreign_key "reports", "accounts", column: "action_taken_by_account_id", on_delete: :nullify
-  add_foreign_key "reports", "accounts", column: "target_account_id", on_delete: :cascade
-  add_foreign_key "reports", "accounts", on_delete: :cascade
-  add_foreign_key "session_activations", "oauth_access_tokens", column: "access_token_id", on_delete: :cascade
-  add_foreign_key "session_activations", "users", on_delete: :cascade
-  add_foreign_key "status_pins", "accounts", on_delete: :cascade
+  add_foreign_key "mutes", "accounts", column: "target_account_id", name: "fk_eecff219ea", on_delete: :cascade
+  add_foreign_key "mutes", "accounts", name: "fk_b8d8daf315", on_delete: :cascade
+  add_foreign_key "notifications", "accounts", column: "from_account_id", name: "fk_fbd6b0bf9e", on_delete: :cascade
+  add_foreign_key "notifications", "accounts", name: "fk_c141c8ee55", on_delete: :cascade
+  add_foreign_key "oauth_access_grants", "oauth_applications", column: "application_id", name: "fk_34d54b0a33", on_delete: :cascade
+  add_foreign_key "oauth_access_grants", "users", column: "resource_owner_id", name: "fk_63b044929b", on_delete: :cascade
+  add_foreign_key "oauth_access_tokens", "oauth_applications", column: "application_id", name: "fk_f5fc4c1ee3", on_delete: :cascade
+  add_foreign_key "oauth_access_tokens", "users", column: "resource_owner_id", name: "fk_e84df68546", on_delete: :cascade
+  add_foreign_key "oauth_applications", "users", column: "owner_id", name: "fk_b0988c7c0a", on_delete: :cascade
+  add_foreign_key "reports", "accounts", column: "action_taken_by_account_id", name: "fk_bca45b75fd", on_delete: :nullify
+  add_foreign_key "reports", "accounts", column: "target_account_id", name: "fk_eb37af34f0", on_delete: :cascade
+  add_foreign_key "reports", "accounts", name: "fk_4b81f7522c", on_delete: :cascade
+  add_foreign_key "session_activations", "oauth_access_tokens", column: "access_token_id", name: "fk_957e5bda89", on_delete: :cascade
+  add_foreign_key "session_activations", "users", name: "fk_e5fda67334", on_delete: :cascade
+  add_foreign_key "status_pins", "accounts", name: "fk_d4cb435b62", on_delete: :cascade
   add_foreign_key "status_pins", "statuses", on_delete: :cascade
-  add_foreign_key "statuses", "accounts", column: "in_reply_to_account_id", on_delete: :nullify
-  add_foreign_key "statuses", "accounts", on_delete: :cascade
+  add_foreign_key "statuses", "accounts", column: "in_reply_to_account_id", name: "fk_c7fa917661", on_delete: :nullify
+  add_foreign_key "statuses", "accounts", name: "fk_9bda1543f7", on_delete: :cascade
   add_foreign_key "statuses", "statuses", column: "in_reply_to_id", on_delete: :nullify
   add_foreign_key "statuses", "statuses", column: "reblog_of_id", on_delete: :cascade
   add_foreign_key "statuses_tags", "statuses", on_delete: :cascade
-  add_foreign_key "statuses_tags", "tags", on_delete: :cascade
-  add_foreign_key "stream_entries", "accounts", on_delete: :cascade
-  add_foreign_key "subscriptions", "accounts", on_delete: :cascade
-  add_foreign_key "users", "accounts", on_delete: :cascade
-  add_foreign_key "web_settings", "users", on_delete: :cascade
+  add_foreign_key "statuses_tags", "tags", name: "fk_3081861e21", on_delete: :cascade
+  add_foreign_key "stream_entries", "accounts", name: "fk_5659b17554", on_delete: :cascade
+  add_foreign_key "subscriptions", "accounts", name: "fk_9847d1cbb5", on_delete: :cascade
+  add_foreign_key "users", "accounts", name: "fk_50500f500d", on_delete: :cascade
+  add_foreign_key "web_settings", "users", name: "fk_11910667b2", on_delete: :cascade
 end
diff --git a/lib/mastodon/migration_helpers.rb b/lib/mastodon/migration_helpers.rb
new file mode 100644
index 000000000..ed716501e
--- /dev/null
+++ b/lib/mastodon/migration_helpers.rb
@@ -0,0 +1,988 @@
+# frozen_string_literal: true
+
+# This file is copied almost entirely from GitLab, which has done a large
+# amount of work to ensure that migrations can happen with minimal downtime.
+# Many thanks to those engineers.
+
+# Changes have been made to remove dependencies on other GitLab files and to
+# shorten temporary column names.
+
+# Documentation on using these functions (and why one might do so):
+# https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/what_requires_downtime.md
+
+# The file itself:
+# https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/gitlab/database/migration_helpers.rb
+
+# It is licensed as follows:
+
+# Copyright (c) 2011-2017 GitLab B.V.
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+# This is bad form, but there are enough differences that it's impractical to do
+# otherwise:
+# rubocop:disable all
+
+module Mastodon
+  module MigrationHelpers
+    # Stub for Database.postgresql? from GitLab
+    def self.postgresql?
+      ActiveRecord::Base.configurations[Rails.env]['adapter'].casecmp('postgresql').zero?
+    end
+
+    # Stub for Database.mysql? from GitLab
+    def self.mysql?
+      ActiveRecord::Base.configurations[Rails.env]['adapter'].casecmp('mysql2').zero?
+    end
+
+    # Model that can be used for querying permissions of a SQL user.
+    class Grant < ActiveRecord::Base
+      self.table_name =
+        if Mastodon::MigrationHelpers.postgresql?
+          'information_schema.role_table_grants'
+        else
+          'mysql.user'
+        end
+
+      def self.scope_to_current_user
+        if Mastodon::MigrationHelpers.postgresql?
+          where('grantee = user')
+        else
+          where("CONCAT(User, '@', Host) = current_user()")
+        end
+      end
+
+      # Returns true if the current user can create and execute triggers on the
+      # given table.
+      def self.create_and_execute_trigger?(table)
+        priv =
+          if Mastodon::MigrationHelpers.postgresql?
+            where(privilege_type: 'TRIGGER', table_name: table)
+          else
+            where(Trigger_priv: 'Y')
+          end
+
+        priv.scope_to_current_user.any?
+      end
+    end
+
+    BACKGROUND_MIGRATION_BATCH_SIZE = 1000 # Number of rows to process per job
+    BACKGROUND_MIGRATION_JOB_BUFFER_SIZE = 1000 # Number of jobs to bulk queue at a time
+    
+    # Gets an estimated number of rows for a table
+    def estimate_rows_in_table(table_name)
+      exec_query('SELECT reltuples FROM pg_class WHERE relname = ' +
+        "'#{table_name}'").to_a.first['reltuples']
+    end
+
+    # Adds `created_at` and `updated_at` columns with timezone information.
+    #
+    # This method is an improved version of Rails' built-in method `add_timestamps`.
+    #
+    # Available options are:
+    # default - The default value for the column.
+    # null - When set to `true` the column will allow NULL values.
+    #        The default is to not allow NULL values.
+    def add_timestamps_with_timezone(table_name, options = {})
+      options[:null] = false if options[:null].nil?
+
+      [:created_at, :updated_at].each do |column_name|
+        if options[:default] && transaction_open?
+          raise '`add_timestamps_with_timezone` with default value cannot be run inside a transaction. ' \
+            'You can disable transactions by calling `disable_ddl_transaction!` ' \
+            'in the body of your migration class'
+        end
+
+        # If default value is presented, use `add_column_with_default` method instead.
+        if options[:default]
+          add_column_with_default(
+            table_name,
+            column_name,
+            :datetime_with_timezone,
+            default: options[:default],
+            allow_null: options[:null]
+          )
+        else
+          add_column(table_name, column_name, :datetime_with_timezone, options)
+        end
+      end
+    end
+
+    # Creates a new index, concurrently when supported
+    #
+    # On PostgreSQL this method creates an index concurrently, on MySQL this
+    # creates a regular index.
+    #
+    # Example:
+    #
+    #     add_concurrent_index :users, :some_column
+    #
+    # See Rails' `add_index` for more info on the available arguments.
+    def add_concurrent_index(table_name, column_name, options = {})
+      if transaction_open?
+        raise 'add_concurrent_index can not be run inside a transaction, ' \
+          'you can disable transactions by calling disable_ddl_transaction! ' \
+          'in the body of your migration class'
+      end
+
+      if MigrationHelpers.postgresql?
+        options = options.merge({ algorithm: :concurrently })
+        disable_statement_timeout
+      end
+
+      add_index(table_name, column_name, options)
+    end
+
+    # Removes an existed index, concurrently when supported
+    #
+    # On PostgreSQL this method removes an index concurrently.
+    #
+    # Example:
+    #
+    #     remove_concurrent_index :users, :some_column
+    #
+    # See Rails' `remove_index` for more info on the available arguments.
+    def remove_concurrent_index(table_name, column_name, options = {})
+      if transaction_open?
+        raise 'remove_concurrent_index can not be run inside a transaction, ' \
+          'you can disable transactions by calling disable_ddl_transaction! ' \
+          'in the body of your migration class'
+      end
+
+      if supports_drop_index_concurrently?
+        options = options.merge({ algorithm: :concurrently })
+        disable_statement_timeout
+      end
+
+      remove_index(table_name, options.merge({ column: column_name }))
+    end
+
+    # Removes an existing index, concurrently when supported
+    #
+    # On PostgreSQL this method removes an index concurrently.
+    #
+    # Example:
+    #
+    #     remove_concurrent_index :users, "index_X_by_Y"
+    #
+    # See Rails' `remove_index` for more info on the available arguments.
+    def remove_concurrent_index_by_name(table_name, index_name, options = {})
+      if transaction_open?
+        raise 'remove_concurrent_index_by_name can not be run inside a transaction, ' \
+          'you can disable transactions by calling disable_ddl_transaction! ' \
+          'in the body of your migration class'
+      end
+
+      if supports_drop_index_concurrently?
+        options = options.merge({ algorithm: :concurrently })
+        disable_statement_timeout
+      end
+
+      remove_index(table_name, options.merge({ name: index_name }))
+    end
+
+    # Only available on Postgresql >= 9.2
+    def supports_drop_index_concurrently?
+      return false unless MigrationHelpers.postgresql?
+
+      version = select_one("SELECT current_setting('server_version_num') AS v")['v'].to_i
+
+      version >= 90200
+    end
+
+    # Adds a foreign key with only minimal locking on the tables involved.
+    #
+    # This method only requires minimal locking when using PostgreSQL. When
+    # using MySQL this method will use Rails' default `add_foreign_key`.
+    #
+    # source - The source table containing the foreign key.
+    # target - The target table the key points to.
+    # column - The name of the column to create the foreign key on.
+    # on_delete - The action to perform when associated data is removed,
+    #             defaults to "CASCADE".
+    def add_concurrent_foreign_key(source, target, column:, on_delete: :cascade, target_col: 'id')
+      # Transactions would result in ALTER TABLE locks being held for the
+      # duration of the transaction, defeating the purpose of this method.
+      if transaction_open?
+        raise 'add_concurrent_foreign_key can not be run inside a transaction'
+      end
+
+      # While MySQL does allow disabling of foreign keys it has no equivalent
+      # of PostgreSQL's "VALIDATE CONSTRAINT". As a result we'll just fall
+      # back to the normal foreign key procedure.
+      if MigrationHelpers.mysql?
+        return add_foreign_key(source, target,
+                               column: column,
+                               on_delete: on_delete)
+      else
+        on_delete = 'SET NULL' if on_delete == :nullify
+      end
+
+      disable_statement_timeout
+
+      key_name = concurrent_foreign_key_name(source, column, target_col)
+
+      # Using NOT VALID allows us to create a key without immediately
+      # validating it. This means we keep the ALTER TABLE lock only for a
+      # short period of time. The key _is_ enforced for any newly created
+      # data.
+      execute <<-EOF.strip_heredoc
+      ALTER TABLE #{source}
+      ADD CONSTRAINT #{key_name}
+      FOREIGN KEY (#{column})
+      REFERENCES #{target} (#{target_col})
+      #{on_delete ? "ON DELETE #{on_delete.upcase}" : ''}
+      NOT VALID;
+      EOF
+
+      # Validate the existing constraint. This can potentially take a very
+      # long time to complete, but fortunately does not lock the source table
+      # while running.
+      execute("ALTER TABLE #{source} VALIDATE CONSTRAINT #{key_name};")
+    end
+
+    # Returns the name for a concurrent foreign key.
+    #
+    # PostgreSQL constraint names have a limit of 63 bytes. The logic used
+    # here is based on Rails' foreign_key_name() method, which unfortunately
+    # is private so we can't rely on it directly.
+    def concurrent_foreign_key_name(table, column, target_col)
+      "fk_#{Digest::SHA256.hexdigest("#{table}_#{column}_#{target_col}_fk").first(10)}"
+    end
+
+    # Long-running migrations may take more than the timeout allowed by
+    # the database. Disable the session's statement timeout to ensure
+    # migrations don't get killed prematurely. (PostgreSQL only)
+    def disable_statement_timeout
+      execute('SET statement_timeout TO 0') if MigrationHelpers.postgresql?
+    end
+
+    # Updates the value of a column in batches.
+    #
+    # This method updates the table in batches of 5% of the total row count.
+    # This method will continue updating rows until no rows remain.
+    #
+    # When given a block this method will yield two values to the block:
+    #
+    # 1. An instance of `Arel::Table` for the table that is being updated.
+    # 2. The query to run as an Arel object.
+    #
+    # By supplying a block one can add extra conditions to the queries being
+    # executed. Note that the same block is used for _all_ queries.
+    #
+    # Example:
+    #
+    #     update_column_in_batches(:projects, :foo, 10) do |table, query|
+    #       query.where(table[:some_column].eq('hello'))
+    #     end
+    #
+    # This would result in this method updating only rows where
+    # `projects.some_column` equals "hello".
+    #
+    # table - The name of the table.
+    # column - The name of the column to update.
+    # value - The value for the column.
+    #
+    # Rubocop's Metrics/AbcSize metric is disabled for this method as Rubocop
+    # determines this method to be too complex while there's no way to make it
+    # less "complex" without introducing extra methods (which actually will
+    # make things _more_ complex).
+    #
+    # rubocop: disable Metrics/AbcSize
+    def update_column_in_batches(table_name, column, value)
+      if transaction_open?
+        raise 'update_column_in_batches can not be run inside a transaction, ' \
+          'you can disable transactions by calling disable_ddl_transaction! ' \
+          'in the body of your migration class'
+      end
+
+      table = Arel::Table.new(table_name)
+      
+      total = estimate_rows_in_table(table_name).to_i
+      if total == 0
+        count_arel = table.project(Arel.star.count.as('count'))
+        count_arel = yield table, count_arel if block_given?
+        
+        total = exec_query(count_arel.to_sql).to_hash.first['count'].to_i
+        
+        return if total == 0
+      end
+
+      # Update in batches of 5% until we run out of any rows to update.
+      batch_size = ((total / 100.0) * 5.0).ceil
+      max_size = 1000
+
+      # The upper limit is 1000 to ensure we don't lock too many rows. For
+      # example, for "merge_requests" even 1% of the table is around 35 000
+      # rows for GitLab.com.
+      batch_size = max_size if batch_size > max_size
+
+      start_arel = table.project(table[:id]).order(table[:id].asc).take(1)
+      start_arel = yield table, start_arel if block_given?
+      start_id = exec_query(start_arel.to_sql).to_hash.first['id'].to_i
+      
+      say "Migrating #{table_name}.#{column} (~#{total.to_i} rows)"
+
+      started_time = Time.now
+      last_time = Time.now
+      migrated = 0
+      loop do
+        stop_row = nil
+        
+        suppress_messages do
+          stop_arel = table.project(table[:id])
+            .where(table[:id].gteq(start_id))
+            .order(table[:id].asc)
+            .take(1)
+            .skip(batch_size)
+
+          stop_arel = yield table, stop_arel if block_given?
+          stop_row = exec_query(stop_arel.to_sql).to_hash.first
+
+          update_arel = Arel::UpdateManager.new
+            .table(table)
+            .set([[table[column], value]])
+            .where(table[:id].gteq(start_id))
+
+          if stop_row
+            stop_id = stop_row['id'].to_i
+            start_id = stop_id
+            update_arel = update_arel.where(table[:id].lt(stop_id))
+          end
+
+          update_arel = yield table, update_arel if block_given?
+
+          execute(update_arel.to_sql)
+        end
+        
+        migrated += batch_size
+        if Time.now - last_time > 1
+          status = "Migrated #{migrated} rows"
+          
+          percentage = 100.0 * migrated / total
+          status += " (~#{sprintf('%.2f', percentage)}%, "
+          
+          remaining_time = (100.0 - percentage) * (Time.now - started_time) / percentage
+          
+          status += "#{(remaining_time / 60).to_i}:"
+          status += sprintf('%02d', remaining_time.to_i % 60)
+          status += ' remaining, '
+          
+          # Tell users not to interrupt if we're almost done.
+          if remaining_time > 10
+            status += 'safe to interrupt'
+          else
+            status += 'DO NOT interrupt'
+          end
+          
+          status += ')'
+          
+          say status, true
+          last_time = Time.now
+        end
+
+        # There are no more rows left to update.
+        break unless stop_row
+      end
+    end
+
+    # Adds a column with a default value without locking an entire table.
+    #
+    # This method runs the following steps:
+    #
+    # 1. Add the column with a default value of NULL.
+    # 2. Change the default value of the column to the specified value.
+    # 3. Update all existing rows in batches.
+    # 4. Set a `NOT NULL` constraint on the column if desired (the default).
+    #
+    # These steps ensure a column can be added to a large and commonly used
+    # table without locking the entire table for the duration of the table
+    # modification.
+    #
+    # table - The name of the table to update.
+    # column - The name of the column to add.
+    # type - The column type (e.g. `:integer`).
+    # default - The default value for the column.
+    # limit - Sets a column limit. For example, for :integer, the default is
+    #         4-bytes. Set `limit: 8` to allow 8-byte integers.
+    # allow_null - When set to `true` the column will allow NULL values, the
+    #              default is to not allow NULL values.
+    #
+    # This method can also take a block which is passed directly to the
+    # `update_column_in_batches` method.
+    def add_column_with_default(table, column, type, default:, limit: nil, allow_null: false, &block)
+      if transaction_open?
+        raise 'add_column_with_default can not be run inside a transaction, ' \
+          'you can disable transactions by calling disable_ddl_transaction! ' \
+          'in the body of your migration class'
+      end
+
+      disable_statement_timeout
+
+      transaction do
+        if limit
+          add_column(table, column, type, default: nil, limit: limit)
+        else
+          add_column(table, column, type, default: nil)
+        end
+
+        # Changing the default before the update ensures any newly inserted
+        # rows already use the proper default value.
+        change_column_default(table, column, default)
+      end
+
+      begin
+        update_column_in_batches(table, column, default, &block)
+
+        change_column_null(table, column, false) unless allow_null
+      # We want to rescue _all_ exceptions here, even those that don't inherit
+      # from StandardError.
+      rescue Exception => error # rubocop: disable all
+        remove_column(table, column)
+
+        raise error
+      end
+    end
+
+    # Renames a column without requiring downtime.
+    #
+    # Concurrent renames work by using database triggers to ensure both the
+    # old and new column are in sync. However, this method will _not_ remove
+    # the triggers or the old column automatically; this needs to be done
+    # manually in a post-deployment migration. This can be done using the
+    # method `cleanup_concurrent_column_rename`.
+    #
+    # table - The name of the database table containing the column.
+    # old - The old column name.
+    # new - The new column name.
+    # type - The type of the new column. If no type is given the old column's
+    #        type is used.
+    def rename_column_concurrently(table, old, new, type: nil)
+      if transaction_open?
+        raise 'rename_column_concurrently can not be run inside a transaction'
+      end
+
+      check_trigger_permissions!(table)
+      trigger_name = rename_trigger_name(table, old, new)
+      
+      # If we were in the middle of update_column_in_batches, we should remove
+      # the old column and start over, as we have no idea where we were.
+      if column_for(table, new)
+        if MigrationHelpers.postgresql?
+          remove_rename_triggers_for_postgresql(table, trigger_name)
+        else
+          remove_rename_triggers_for_mysql(trigger_name)
+        end
+        
+        remove_column(table, new)
+      end
+
+      old_col = column_for(table, old)
+      new_type = type || old_col.type
+
+      col_opts = {
+        precision: old_col.precision,
+        scale: old_col.scale,
+      }
+
+      # We may be trying to reset the limit on an integer column type, so let
+      # Rails handle that.
+      unless [:bigint, :integer].include?(new_type)
+        col_opts[:limit] = old_col.limit
+      end
+
+      add_column(table, new, new_type, col_opts)
+
+      # We set the default value _after_ adding the column so we don't end up
+      # updating any existing data with the default value. This isn't
+      # necessary since we copy over old values further down.
+      change_column_default(table, new, old_col.default) if old_col.default
+
+      quoted_table = quote_table_name(table)
+      quoted_old = quote_column_name(old)
+      quoted_new = quote_column_name(new)
+
+      if MigrationHelpers.postgresql?
+        install_rename_triggers_for_postgresql(trigger_name, quoted_table,
+                                               quoted_old, quoted_new)
+      else
+        install_rename_triggers_for_mysql(trigger_name, quoted_table,
+                                          quoted_old, quoted_new)
+      end
+
+      update_column_in_batches(table, new, Arel::Table.new(table)[old])
+
+      change_column_null(table, new, false) unless old_col.null
+
+      copy_indexes(table, old, new)
+      copy_foreign_keys(table, old, new)
+    end
+
+    # Changes the type of a column concurrently.
+    #
+    # table - The table containing the column.
+    # column - The name of the column to change.
+    # new_type - The new column type.
+    def change_column_type_concurrently(table, column, new_type)
+      temp_column = rename_column_name(column)
+
+      rename_column_concurrently(table, column, temp_column, type: new_type)
+      
+      # Primary keys don't necessarily have an associated index.
+      if ActiveRecord::Base.get_primary_key(table) == column.to_s
+        old_pk_index_name = "index_#{table}_on_#{column}"
+        new_pk_index_name = "index_#{table}_on_#{column}_cm"
+        
+        unless indexes_for(table, column).find{|i| i.name == old_pk_index_name}
+          add_concurrent_index(table, [temp_column], {
+            unique: true,
+            name: new_pk_index_name
+          })
+        end
+      end
+    end
+
+    # Performs cleanup of a concurrent type change.
+    #
+    # table - The table containing the column.
+    # column - The name of the column to change.
+    # new_type - The new column type.
+    def cleanup_concurrent_column_type_change(table, column)
+      temp_column = rename_column_name(column)
+
+      # Wait for the indices to be built
+      indexes_for(table, column).each do |index|
+        expected_name = index.name + '_cm'
+        
+        puts "Waiting for index #{expected_name}"
+        sleep 1 until indexes_for(table, temp_column).find {|i| i.name == expected_name }
+      end
+      
+      was_primary = (ActiveRecord::Base.get_primary_key(table) == column.to_s)
+      old_default_fn = column_for(table, column).default_function
+      
+      old_fks = []
+      if was_primary
+        # Get any foreign keys pointing at this column we need to recreate, and
+        # remove the old ones.
+        # Based on code from:
+        # http://errorbank.blogspot.com/2011/03/list-all-foreign-keys-references-for.html
+        old_fks_res = execute <<-EOF.strip_heredoc
+          select m.relname as src_table,
+            (select a.attname
+              from pg_attribute a
+              where a.attrelid = m.oid
+                and a.attnum = o.conkey[1]
+                and a.attisdropped = false) as src_col,
+            o.conname as name,
+            o.confdeltype as on_delete
+          from pg_constraint o
+          left join pg_class f on f.oid = o.confrelid 
+          left join pg_class c on c.oid = o.conrelid
+          left join pg_class m on m.oid = o.conrelid
+          where o.contype = 'f'
+            and o.conrelid in (
+              select oid from pg_class c where c.relkind = 'r')
+            and f.relname = '#{table}';
+          EOF
+        old_fks = old_fks_res.to_a
+        old_fks.each do |old_fk|
+          add_concurrent_foreign_key(
+            old_fk['src_table'],
+            table,
+            column: old_fk['src_col'],
+            target_col: temp_column,
+            on_delete: extract_foreign_key_action(old_fk['on_delete'])
+          )
+          
+          remove_foreign_key(old_fk['src_table'], name: old_fk['name'])
+        end
+      end
+
+      # If there was a sequence owned by the old column, make it owned by the
+      # new column, as it will otherwise be deleted when we get rid of the
+      # old column.
+      if (seq_match = /^nextval\('([^']*)'(::text|::regclass)?\)/.match(old_default_fn))
+        seq_name = seq_match[1]
+        execute("ALTER SEQUENCE #{seq_name} OWNED BY #{table}.#{temp_column}")
+      end
+
+      transaction do
+        # This has to be performed in a transaction as otherwise we might have
+        # inconsistent data.
+        
+        cleanup_concurrent_column_rename(table, column, temp_column)
+        rename_column(table, temp_column, column)
+        
+        # If there was an old default function, we didn't copy it. Do that now
+        # in the transaction, so we don't miss anything.
+        change_column_default(table, column, -> { old_default_fn }) if old_default_fn
+      end
+      
+      # Rename any indices back to what they should be.
+      indexes_for(table, column).each do |index|
+        next unless index.name.end_with?('_cm')
+
+        real_index_name = index.name.sub(/_cm$/, '')
+        rename_index(table, index.name, real_index_name)
+      end
+      
+      # Rename any foreign keys back to names based on the real column.
+      foreign_keys_for(table, column).each do |fk|
+        old_fk_name = concurrent_foreign_key_name(fk.from_table, temp_column, 'id')
+        new_fk_name = concurrent_foreign_key_name(fk.from_table, column, 'id')
+        execute("ALTER TABLE #{fk.from_table} RENAME CONSTRAINT " +
+          "#{old_fk_name} TO #{new_fk_name}")
+      end
+      
+      # Rename any foreign keys from other tables to names based on the real
+      # column.
+      old_fks.each do |old_fk|
+        old_fk_name = concurrent_foreign_key_name(old_fk['src_table'],
+          old_fk['src_col'], temp_column)
+        new_fk_name = concurrent_foreign_key_name(old_fk['src_table'],
+          old_fk['src_col'], column)
+        execute("ALTER TABLE #{old_fk['src_table']} RENAME CONSTRAINT " +
+          "#{old_fk_name} TO #{new_fk_name}")
+      end
+      
+      # If the old column was a primary key, mark the new one as a primary key.
+      if was_primary
+        execute("ALTER TABLE #{table} ADD PRIMARY KEY USING INDEX " +
+          "index_#{table}_on_#{column}")
+      end
+    end
+
+    # Cleans up a concurrent column name.
+    #
+    # This method takes care of removing previously installed triggers as well
+    # as removing the old column.
+    #
+    # table - The name of the database table.
+    # old - The name of the old column.
+    # new - The name of the new column.
+    def cleanup_concurrent_column_rename(table, old, new)
+      trigger_name = rename_trigger_name(table, old, new)
+
+      check_trigger_permissions!(table)
+
+      if MigrationHelpers.postgresql?
+        remove_rename_triggers_for_postgresql(table, trigger_name)
+      else
+        remove_rename_triggers_for_mysql(trigger_name)
+      end
+
+      remove_column(table, old)
+    end
+
+    # Performs a concurrent column rename when using PostgreSQL.
+    def install_rename_triggers_for_postgresql(trigger, table, old, new)
+      execute <<-EOF.strip_heredoc
+      CREATE OR REPLACE FUNCTION #{trigger}()
+      RETURNS trigger AS
+      $BODY$
+      BEGIN
+        NEW.#{new} := NEW.#{old};
+        RETURN NEW;
+      END;
+      $BODY$
+      LANGUAGE 'plpgsql'
+      VOLATILE
+      EOF
+
+      execute <<-EOF.strip_heredoc
+      CREATE TRIGGER #{trigger}
+      BEFORE INSERT OR UPDATE
+      ON #{table}
+      FOR EACH ROW
+      EXECUTE PROCEDURE #{trigger}()
+      EOF
+    end
+
+    # Installs the triggers necessary to perform a concurrent column rename on
+    # MySQL.
+    def install_rename_triggers_for_mysql(trigger, table, old, new)
+      execute <<-EOF.strip_heredoc
+      CREATE TRIGGER #{trigger}_insert
+      BEFORE INSERT
+      ON #{table}
+      FOR EACH ROW
+      SET NEW.#{new} = NEW.#{old}
+      EOF
+
+      execute <<-EOF.strip_heredoc
+      CREATE TRIGGER #{trigger}_update
+      BEFORE UPDATE
+      ON #{table}
+      FOR EACH ROW
+      SET NEW.#{new} = NEW.#{old}
+      EOF
+    end
+
+    # Removes the triggers used for renaming a PostgreSQL column concurrently.
+    def remove_rename_triggers_for_postgresql(table, trigger)
+      execute("DROP TRIGGER IF EXISTS #{trigger} ON #{table}")
+      execute("DROP FUNCTION IF EXISTS #{trigger}()")
+    end
+
+    # Removes the triggers used for renaming a MySQL column concurrently.
+    def remove_rename_triggers_for_mysql(trigger)
+      execute("DROP TRIGGER IF EXISTS #{trigger}_insert")
+      execute("DROP TRIGGER IF EXISTS #{trigger}_update")
+    end
+
+    # Returns the (base) name to use for triggers when renaming columns.
+    def rename_trigger_name(table, old, new)
+      'trigger_' + Digest::SHA256.hexdigest("#{table}_#{old}_#{new}").first(12)
+    end
+
+    # Returns the name to use for temporary rename columns.
+    def rename_column_name(base)
+      base.to_s + '_cm'
+    end
+
+    # Returns an Array containing the indexes for the given column
+    def indexes_for(table, column)
+      column = column.to_s
+
+      indexes(table).select { |index| index.columns.include?(column) }
+    end
+
+    # Returns an Array containing the foreign keys for the given column.
+    def foreign_keys_for(table, column)
+      column = column.to_s
+
+      foreign_keys(table).select { |fk| fk.column == column }
+    end
+
+    # Copies all indexes for the old column to a new column.
+    #
+    # table - The table containing the columns and indexes.
+    # old - The old column.
+    # new - The new column.
+    def copy_indexes(table, old, new)
+      old = old.to_s
+      new = new.to_s
+
+      indexes_for(table, old).each do |index|
+        new_columns = index.columns.map do |column|
+          column == old ? new : column
+        end
+
+        # This is necessary as we can't properly rename indexes such as
+        # "ci_taggings_idx".
+        name = index.name + '_cm'
+        
+        # If the order contained the old column, map it to the new one.
+        order = index.orders
+        if order.key?(old)
+          order[new] = order.delete(old)
+        end
+
+        options = {
+          unique: index.unique,
+          name: name,
+          length: index.lengths,
+          order: order
+        }
+
+        # These options are not supported by MySQL, so we only add them if
+        # they were previously set.
+        options[:using] = index.using if index.using
+        options[:where] = index.where if index.where
+
+        add_concurrent_index(table, new_columns, options)
+      end
+    end
+
+    # Copies all foreign keys for the old column to the new column.
+    #
+    # table - The table containing the columns and indexes.
+    # old - The old column.
+    # new - The new column.
+    def copy_foreign_keys(table, old, new)
+      foreign_keys_for(table, old).each do |fk|
+        add_concurrent_foreign_key(fk.from_table,
+                                   fk.to_table,
+                                   column: new,
+                                   on_delete: fk.on_delete)
+      end
+    end
+
+    # Returns the column for the given table and column name.
+    def column_for(table, name)
+      name = name.to_s
+
+      columns(table).find { |column| column.name == name }
+    end
+
+    # This will replace the first occurance of a string in a column with
+    # the replacement
+    # On postgresql we can use `regexp_replace` for that.
+    # On mysql we find the location of the pattern, and overwrite it
+    # with the replacement
+    def replace_sql(column, pattern, replacement)
+      quoted_pattern = Arel::Nodes::Quoted.new(pattern.to_s)
+      quoted_replacement = Arel::Nodes::Quoted.new(replacement.to_s)
+
+      if MigrationHelpers.mysql?
+        locate = Arel::Nodes::NamedFunction
+          .new('locate', [quoted_pattern, column])
+        insert_in_place = Arel::Nodes::NamedFunction
+          .new('insert', [column, locate, pattern.size, quoted_replacement])
+
+        Arel::Nodes::SqlLiteral.new(insert_in_place.to_sql)
+      else
+        replace = Arel::Nodes::NamedFunction
+          .new("regexp_replace", [column, quoted_pattern, quoted_replacement])
+        Arel::Nodes::SqlLiteral.new(replace.to_sql)
+      end
+    end
+
+    def remove_foreign_key_without_error(*args)
+      remove_foreign_key(*args)
+    rescue ArgumentError
+    end
+
+    def sidekiq_queue_migrate(queue_from, to:)
+      while sidekiq_queue_length(queue_from) > 0
+        Sidekiq.redis do |conn|
+          conn.rpoplpush "queue:#{queue_from}", "queue:#{to}"
+        end
+      end
+    end
+
+    def sidekiq_queue_length(queue_name)
+      Sidekiq.redis do |conn|
+        conn.llen("queue:#{queue_name}")
+      end
+    end
+
+    def check_trigger_permissions!(table)
+      unless Grant.create_and_execute_trigger?(table)
+        dbname = ActiveRecord::Base.configurations[Rails.env]['database']
+        user = ActiveRecord::Base.configurations[Rails.env]['username'] || ENV['USER']
+
+        raise <<-EOF
+Your database user is not allowed to create, drop, or execute triggers on the
+table #{table}.
+
+If you are using PostgreSQL you can solve this by logging in to the GitLab
+database (#{dbname}) using a super user and running:
+
+    ALTER #{user} WITH SUPERUSER
+
+For MySQL you instead need to run:
+
+    GRANT ALL PRIVILEGES ON *.* TO #{user}@'%'
+
+Both queries will grant the user super user permissions, ensuring you don't run
+into similar problems in the future (e.g. when new tables are created).
+        EOF
+      end
+    end
+
+    # Bulk queues background migration jobs for an entire table, batched by ID range.
+    # "Bulk" meaning many jobs will be pushed at a time for efficiency.
+    # If you need a delay interval per job, then use `queue_background_migration_jobs_by_range_at_intervals`.
+    #
+    # model_class - The table being iterated over
+    # job_class_name - The background migration job class as a string
+    # batch_size - The maximum number of rows per job
+    #
+    # Example:
+    #
+    #     class Route < ActiveRecord::Base
+    #       include EachBatch
+    #       self.table_name = 'routes'
+    #     end
+    #
+    #     bulk_queue_background_migration_jobs_by_range(Route, 'ProcessRoutes')
+    #
+    # Where the model_class includes EachBatch, and the background migration exists:
+    #
+    #     class Gitlab::BackgroundMigration::ProcessRoutes
+    #       def perform(start_id, end_id)
+    #         # do something
+    #       end
+    #     end
+    def bulk_queue_background_migration_jobs_by_range(model_class, job_class_name, batch_size: BACKGROUND_MIGRATION_BATCH_SIZE)
+      raise "#{model_class} does not have an ID to use for batch ranges" unless model_class.column_names.include?('id')
+
+      jobs = []
+
+      model_class.each_batch(of: batch_size) do |relation|
+        start_id, end_id = relation.pluck('MIN(id), MAX(id)').first
+
+        if jobs.length >= BACKGROUND_MIGRATION_JOB_BUFFER_SIZE
+          # Note: This code path generally only helps with many millions of rows
+          # We push multiple jobs at a time to reduce the time spent in
+          # Sidekiq/Redis operations. We're using this buffer based approach so we
+          # don't need to run additional queries for every range.
+          BackgroundMigrationWorker.perform_bulk(jobs)
+          jobs.clear
+        end
+
+        jobs << [job_class_name, [start_id, end_id]]
+      end
+
+      BackgroundMigrationWorker.perform_bulk(jobs) unless jobs.empty?
+    end
+
+    # Queues background migration jobs for an entire table, batched by ID range.
+    # Each job is scheduled with a `delay_interval` in between.
+    # If you use a small interval, then some jobs may run at the same time.
+    #
+    # model_class - The table being iterated over
+    # job_class_name - The background migration job class as a string
+    # delay_interval - The duration between each job's scheduled time (must respond to `to_f`)
+    # batch_size - The maximum number of rows per job
+    #
+    # Example:
+    #
+    #     class Route < ActiveRecord::Base
+    #       include EachBatch
+    #       self.table_name = 'routes'
+    #     end
+    #
+    #     queue_background_migration_jobs_by_range_at_intervals(Route, 'ProcessRoutes', 1.minute)
+    #
+    # Where the model_class includes EachBatch, and the background migration exists:
+    #
+    #     class Gitlab::BackgroundMigration::ProcessRoutes
+    #       def perform(start_id, end_id)
+    #         # do something
+    #       end
+    #     end
+    def queue_background_migration_jobs_by_range_at_intervals(model_class, job_class_name, delay_interval, batch_size: BACKGROUND_MIGRATION_BATCH_SIZE)
+      raise "#{model_class} does not have an ID to use for batch ranges" unless model_class.column_names.include?('id')
+
+      model_class.each_batch(of: batch_size) do |relation, index|
+        start_id, end_id = relation.pluck('MIN(id), MAX(id)').first
+
+        # `BackgroundMigrationWorker.bulk_perform_in` schedules all jobs for
+        # the same time, which is not helpful in most cases where we wish to
+        # spread the work over time.
+        BackgroundMigrationWorker.perform_in(delay_interval * index, job_class_name, [start_id, end_id])
+      end
+    end
+  end
+end
+
+# rubocop:enable all