code: func (tmp *TieredMergePolicy) SetFloorSegmentMB(v float64) *TieredMergePolicy {
  	assert2(v > 0, fmt.Sprintf("floorSegmentMB must be > 0 (got %v)", v))
  	v *= 1024 * 1024
  	tmp.floorSegmentBytes = math.MaxInt64
  	if v < math.MaxInt64 {
  		tmp.floorSegmentBytes = int64(v)
  	}
  	return tmp
  }
docs: /*
  Segments smaller than this are "rounded up" to this size, ie treated
  as equal (floor) size for merge selection. This is to prevent
  frequent flushing of tiny segments from allowing a long tail in the
  index. Default is 2 MB.
  */