code: func adjustRowValuesBuf(writeBufs *variable.WriteStmtBufs, rowLen int) {
  	adjustLen := rowLen * 2
  	if writeBufs.AddRowValues == nil || cap(writeBufs.AddRowValues) < adjustLen {
  		writeBufs.AddRowValues = make([]types.Datum, adjustLen)
  	}
  	writeBufs.AddRowValues = writeBufs.AddRowValues[:adjustLen]
  }
docs: // adjustRowValuesBuf adjust writeBufs.AddRowValues length, AddRowValues stores the inserting values that is used
  // by tablecodec.EncodeRow, the encoded row format is `id1, colval, id2, colval`, so the correct length is rowLen * 2. If
  // the inserting row has null value, AddRecord will skip it, so the rowLen will be different, so we need to adjust it.