Function SUnion

command/sets.go:158–202

SUnion returns the members of the set resulting from the union of all the given sets.

(ctx *Context, txn *db.Transaction)

// SUnion returns the members of the set resulting from the union of all the given sets.
func SUnion(ctx *Context, txn *db.Transaction) (OnCommit, error) {
	var members [][]byte
	var setsIter []*db.SetIter
	for _, 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 !set.Exists() {
			continue
		}
		siter, err := set.Iter()
		if err != nil {
			return nil, errors.New("ERR " + err.Error())
		}
		defer siter.Iter.Close()
		setsIter = append(setsIter, siter)
	}

	h := MinHeap(setsIter)
	heap.Init(&h)
	var last []byte
	for len(h) != 0 {
		min := h[0].Value()

		// ignore the duplicated member
		if last == nil || !bytes.Equal(min, last) {
			members = append(members, min)
		}
		last = 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
}

type MinHeap []*db.SetIter