storage/buffer.go
func NewBufferIterator(it SeriesIterator, delta int64) *BufferedSeriesIterator {
	bit := &BufferedSeriesIterator{
		buf:   newSampleRing(delta, 16),
		delta: delta,
	}
	bit.Reset(it)

	return bit
}
func NewBufferIterator(it SeriesIterator, delta int64) *BufferedSeriesIterator {
	bit := &BufferedSeriesIterator{
		buf:   newSampleRing(delta, 16),
		delta: delta,
	}
	bit.Reset(it)

	return bit
}
// NewBufferIterator returns a new iterator that buffers the values within the
// time range of the current element and the duration of delta before.