Function SInter

command/sets.go:223–275

SInter returns the members of the set resulting from the intersection of all the given sets.

(ctx *Context, txn *db.Transaction)

// SInter returns the members of the set resulting from the intersection of all the given sets.
func SInter(ctx *Context, txn *db.Transaction) (OnCommit, error) {
	var members [][]byte
	setsIter := make([]*db.SetIter, len(ctx.Args))
	for i, key := range ctx.Args {
		set, err := txn.Set([]byte(key))
		if err != nil {
			if err == db.ErrTypeMismatch {
				return nil, ErrTypeMismatch
			}
			return nil, errors.New("ERR " + err.Error())
		}
		// If the set corresponding to key does not exist, it is processed as an empty set
		if !set.Exists() {
			return BytesArray(ctx.Out, members), nil
		}
		siter, err := set.Iter()
		if err != nil {
			return nil, errors.New("ERR " + err.Error())
		}
		defer siter.Iter.Close()
		setsIter[i] = siter
	}

	h := MinHeap(setsIter)
	heap.Init(&h)
	var last []byte
	k := len(h) //k-way merge
	n := k
	for len(h) != 0 {
		min := h[0].Value()
		if last == nil || bytes.Equal(last, min) {
			n--
		} else {
			n = k - 1
		}
		last = min

		// it is a member of intersection if there are k equal values continuously
		if n == 0 {
			members = append(members, min)
		}

		if err := h[0].Iter.Next(); err != nil {
			return nil, err
		}
		if h[0].Valid() {
			heap.Fix(&h, 0)
		} else {
			heap.Remove(&h, 0)
		}
	}
	return BytesArray(ctx.Out, members), nil
}

// SDiff returns the members of the set resulting from the difference between the first set and all the successive sets.
func SDiff(ctx *Context, txn *db.Transaction) (OnCommit, error) {