code: func newContext(store kv.Storage) sessionctx.Context {
  	c := mock.NewContext()
  	c.Store = store
  	c.GetSessionVars().SetStatusFlag(mysql.ServerStatusAutocommit, false)
  	c.GetSessionVars().StmtCtx.TimeZone = time.UTC
  	return c
  }
docs: // newContext gets a context. It is only used for adding column in reorganization state.