return await db.collection('chatmsg').match({

        fromopenId: event.toopenId,

      }).aggregate().group({

        _id: {

          toopenId: '$toopenId',

          toavatar: '$toavatar',

          tonickName: '$tonickName',

          tosex: '$tosex'

        },

        totalreadstate: $.sum('$readstate')

        }).end()