storage/buffer.go
func (b *BufferedSeriesIterator) Seek(t int64) bool {
	t0 := t - b.buf.delta

	// If the delta would cause us to seek backwards, preserve the buffer
	// and just continue regular advancement while filling the buffer on the way.
	if t0 > b.lastTime {
		b.buf.reset()

		b.ok = b.it.Seek(t0)
		if !b.ok {
			return false
		}
		b.lastTime, _ = b.Values()
	}

	if b.lastTime >= t {
		return true
	}
	for b.Next() {
		if b.lastTime >= t {
			return true
		}
	}

	return false
}
func (b *BufferedSeriesIterator) Seek(t int64) bool {
	t0 := t - b.buf.delta

	// If the delta would cause us to seek backwards, preserve the buffer
	// and just continue regular advancement while filling the buffer on the way.
	if t0 > b.lastTime {
		b.buf.reset()

		b.ok = b.it.Seek(t0)
		if !b.ok {
			return false
		}
		b.lastTime, _ = b.Values()
	}

	if b.lastTime >= t {
		return true
	}
	for b.Next() {
		if b.lastTime >= t {
			return true
		}
	}

	return false
}
// Seek advances the iterator to the element at time t or greater.