storage/buffer.go
func (b *BufferedSeriesIterator) ReduceDelta(delta int64) bool {
	return b.buf.reduceDelta(delta)
}
func (b *BufferedSeriesIterator) ReduceDelta(delta int64) bool {
	return b.buf.reduceDelta(delta)
}
// ReduceDelta lowers the buffered time delta, for the current SeriesIterator only.