code: func (tmp *TieredMergePolicy) SetMaxMergedSegmentMB(v float64) *TieredMergePolicy {
  	assert2(v >= 0, fmt.Sprintf("maxMergedSegmentMB must be >= 0 (got %v)", v))
  	v *= 1024 * 1024
  	tmp.maxMergedSegmentBytes = math.MaxInt64
  	if v < math.MaxInt64 {
  		tmp.maxMergedSegmentBytes = int64(v)
  	}
  	return tmp
  }
docs: /*
  Maximum sized segment to produce during normal merging. This setting
  is approximate: the estimate of the merged segment size is made by
  summing sizes of to-be-merged segments(compensating for percent
  deleted docs). Default is 5 GB.
  */