Add migration to steal FillStoreUpload

db/post_migrate/20181105201455_steal_fill_store_upload.rb

+# frozen_string_literal: true
+
+class StealFillStoreUpload < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 10_000
+
+  disable_ddl_transaction!
+
+  class Upload < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'uploads'
+    self.inheritance_column = :_type_disabled # Disable STI
+  end
+
+  def up
+    Gitlab::BackgroundMigration.steal('FillStoreUpload')
+
+    Upload.where(store: nil).each_batch(of: BATCH_SIZE) do |batch|
+      range = batch.pluck('MIN(id)', 'MAX(id)').first
+
+      Gitlab::BackgroundMigration::FillStoreUpload.new.perform(*range)
+    end
+  end
+
+  def down
+    # noop
+  end
+end

spec/migrations/steal_fill_store_upload_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20181105201455_steal_fill_store_upload.rb')
+
+describe StealFillStoreUpload, :migration do
+  let(:uploads) { table(:uploads) }
+
+  describe '#up' do
+    it 'steals the FillStoreUpload background migration' do
+      expect(Gitlab::BackgroundMigration).to receive(:steal).with('FillStoreUpload').and_call_original
+
+      migrate!
+    end
+
+    it 'does not run migration if not needed' do
+      uploads.create(size: 100.kilobytes,
+                     uploader: 'AvatarUploader',
+                     path: 'uploads/-/system/avatar.jpg',
+                     store: 1)
+
+      expect_any_instance_of(Gitlab::BackgroundMigration::FillStoreUpload).not_to receive(:perform)
+
+      migrate!
+    end
+
+    it 'ensures all rows are migrated' do
+      uploads.create(size: 100.kilobytes,
+                     uploader: 'AvatarUploader',
+                     path: 'uploads/-/system/avatar.jpg',
+                     store: nil)
+
+      expect_any_instance_of(Gitlab::BackgroundMigration::FillStoreUpload).to receive(:perform).and_call_original
+
+      expect do
+        migrate!
+      end.to change { uploads.where(store: nil).count }.from(1).to(0)
+    end
+  end
+end