Backfill default namespace as User namespace

Changelog: other

db/post_migrate/20210930211936_backfill_user_namespace.rb

+# frozen_string_literal: true
+
+class BackfillUserNamespace < Gitlab::Database::Migration[1.0]
+  MIGRATION = 'BackfillUserNamespace'
+  INTERVAL = 2.minutes
+  BATCH_SIZE = 10_000
+  DOWNTIME = false
+
+  def up
+    queue_batched_background_migration(
+      MIGRATION,
+      :namespaces,
+      :id,
+      job_interval: INTERVAL,
+      batch_size: BATCH_SIZE
+    )
+  end
+
+  def down
+    Gitlab::Database::BackgroundMigration::BatchedMigration
+      .for_configuration(MIGRATION, :namespaces, :id, [])
+      .delete_all
+  end
+end

db/schema_migrations/20210930211936

+3aaf2a4fa834331768e2acc10f67b8d456e70aca9784787e40b55dade7b6f64c
\ No newline at end of file

lib/gitlab/background_migration/backfill_user_namespace.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module BackgroundMigration
+    # Backfills the `namespaces.type` column, replacing any
+    # instances of `NULL` with `User`
+    class BackfillUserNamespace
+      def perform(start_id, stop_id, *args)
+        ActiveRecord::Base.connection.execute(<<~SQL)
+          UPDATE namespaces SET type = 'User'
+          WHERE id BETWEEN #{start_id} AND #{stop_id}
+            AND type IS NULL
+        SQL
+      end
+    end
+  end
+end

spec/lib/gitlab/background_migration/backfill_user_namespace_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::BackgroundMigration::BackfillUserNamespace do
+  let(:migration) { described_class.new }
+  let(:namespaces) { table(:namespaces) }
+
+  before do
+    namespaces.create!(id: 1, name: 'test1', path: 'test1', type: nil)
+    namespaces.create!(id: 2, name: 'test2', path: 'test2', type: 'User')
+    namespaces.create!(id: 3, name: 'test3', path: 'test3', type: 'Group')
+    namespaces.create!(id: 4, name: 'test4', path: 'test4', type: nil)
+    namespaces.create!(id: 11, name: 'test11', path: 'test11', type: nil)
+  end
+
+  it 'backfills `type_new` for the selected records' do
+    queries = ActiveRecord::QueryRecorder.new do
+      migration.perform(1, 10)
+    end
+
+    expect(queries.count).to be(1)
+    expect(Namespace.where(type: 'User').count).to eq 3
+  end
+end

spec/migrations/backfill_user_namespace_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require_migration!
+
+RSpec.describe BackfillUserNamespace do
+  let_it_be(:migration) { described_class::MIGRATION }
+
+  describe '#up' do
+    it 'schedules background jobs for each batch of namespaces' do
+      migrate!
+
+      expect(migration).to have_scheduled_batched_migration(
+        table_name: :namespaces,
+        column_name: :id,
+        interval: described_class::INTERVAL
+      )
+    end
+  end
+
+  describe '#down' do
+    it 'deletes all batched migration records' do
+      migrate!
+      schema_migrate_down!
+
+      expect(migration).not_to have_scheduled_batched_migration
+    end
+  end
+end