1 files changed, 40 insertions, 0 deletions
diff --git a/db/post_migrate/20201104124300_ensure_namespace_settings_creation.rb b/db/post_migrate/20201104124300_ensure_namespace_settings_creation.rb
new file mode 100644
index 00000000000..08f92d21f44
--- /dev/null
+++ b/db/post_migrate/20201104124300_ensure_namespace_settings_creation.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+class EnsureNamespaceSettingsCreation < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 10000
+  MIGRATION = 'BackfillNamespaceSettings'
+  DELAY_INTERVAL = 2.minutes.to_i
+
+  disable_ddl_transaction!
+
+  class Namespace < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'namespaces'
+  end
+
+  def up
+    ensure_data_migration
+  end
+
+  def down
+    # no-op
+  end
+
+  private
+
+  def ensure_data_migration
+    Namespace.each_batch(of: BATCH_SIZE) do |query, index|
+      missing_count = query.where("NOT EXISTS (SELECT 1 FROM namespace_settings WHERE namespace_settings.namespace_id=namespaces.id)").limit(1).size
+
+      if missing_count > 0
+        ids_range = query.pluck("MIN(id), MAX(id)").flatten
+
+        migrate_in(index * DELAY_INTERVAL, MIGRATION, ids_range)
+      end
+    end
+  end
+end