code: private void setToRowStart(RowIndexEntry rowEntry, FileDataInput in) throws IOException
      {
          if (in == null)
          {
              this.file = sstable.getFileDataInput(rowEntry.position);
          }
          else
          {
              this.file = in;
              in.seek(rowEntry.position);
          }
          sstable.partitioner.decorateKey(ByteBufferUtil.readWithShortLength(file));
      }
docs: Sets the seek position to the start of the row for column scanning.