func ParseJSONToQuadList(jsonBody []byte) (out []quad.Quad, _ error) {
	var quads []struct {
		Subject   string `json:"subject"`
		Predicate string `json:"predicate"`
		Object    string `json:"object"`
		Label     string `json:"label"`
	}
	err := json.Unmarshal(jsonBody, &quads)
	if err != nil {
		return nil, err
	}
	out = make([]quad.Quad, 0, len(quads))
	for i, jq := range quads {
		q := quad.Quad{
			Subject:   quad.StringToValue(jq.Subject),
			Predicate: quad.StringToValue(jq.Predicate),
			Object:    quad.StringToValue(jq.Object),
			Label:     quad.StringToValue(jq.Label),
		}
		if !q.IsValid() {
			return nil, fmt.Errorf("invalid quad at index %d. %s", i, q)
		}
		out = append(out, q)
	}
	return out, nil
}

func (qs *QuadStore) indexOf(t quad.Quad) (int64, bool) {
	min := maxInt
	var tree *b.Tree
	for d := quad.Subject; d <= quad.Label; d++ {
		sid := t.Get(d)
		if d == quad.Label && sid == "" {
			continue
		}
		id, ok := qs.idMap[sid]
		// If we've never heard about a node, it must not exist
		if !ok {
			return 0, false
		}
		index, ok := qs.index.Get(d, id)
		if !ok {
			// If it's never been indexed in this direction, it can't exist.
			return 0, false
		}
		if l := index.Len(); l < min {
			min, tree = l, index
		}
	}

	it := NewIterator(tree, qs, 0, 0)
	for it.Next() {
		val := it.Result()
		if t == qs.log[val.(int64)].Quad {
			return val.(int64), true
		}
	}
	return 0, false
}

func (qs *QuadStore) createKeyFor(d [4]quad.Direction, q quad.Quad) []byte {
	key := make([]byte, 0, (hashSize * 4))
	key = append(key, hashOf(q.Get(d[0]))...)
	key = append(key, hashOf(q.Get(d[1]))...)
	key = append(key, hashOf(q.Get(d[2]))...)
	key = append(key, hashOf(q.Get(d[3]))...)
	return key
}

func (qs *QuadStore) createKeyFor(d [4]quad.Direction, q quad.Quad) []byte {
	key := make([]byte, quad.HashSize*4)
	quad.HashTo(q.Get(d[0]), key[quad.HashSize*0:quad.HashSize*1])
	quad.HashTo(q.Get(d[1]), key[quad.HashSize*1:quad.HashSize*2])
	quad.HashTo(q.Get(d[2]), key[quad.HashSize*2:quad.HashSize*3])
	quad.HashTo(q.Get(d[3]), key[quad.HashSize*3:quad.HashSize*4])
	return key
}

func (l *SQLLinkIterator) buildResult(result []string, cols []string) map[string]string {
	var q quad.Quad
	q.Subject = result[0]
	q.Predicate = result[1]
	q.Object = result[2]
	q.Label = result[3]
	l.resultQuad = q
	m := make(map[string]string)
	for i, c := range cols[4:] {
		m[c] = result[i+4]
	}
	return m
}

func (qs *QuadStore) buildQuadWrite(tx *bolt.Tx, q quad.Quad, id int64, isAdd bool) error {
	var entry proto.HistoryEntry
	b := tx.Bucket(spoBucket)
	b.FillPercent = localFillPercent
	data := b.Get(qs.createKeyFor(spo, q))
	if data != nil {
		// We got something.
		err := entry.Unmarshal(data)
		if err != nil {
			return err
		}
	}

	if isAdd && len(entry.History)%2 == 1 {
		clog.Errorf("attempt to add existing quad %v: %#v", entry, q)
		return graph.ErrQuadExists
	}
	if !isAdd && len(entry.History)%2 == 0 {
		clog.Errorf("attempt to delete non-existent quad %v: %#v", entry, q)
		return graph.ErrQuadNotExist
	}

	entry.History = append(entry.History, uint64(id))

	bytes, err := entry.Marshal()
	if err != nil {
		clog.Errorf("Couldn't write to buffer for entry %#v: %s", entry, err)
		return err
	}
	for _, index := range [][4]quad.Direction{spo, osp, pos, cps} {
		if index == cps && q.Get(quad.Label) == "" {
			continue
		}
		b := tx.Bucket(bucketFor(index))
		b.FillPercent = localFillPercent
		err = b.Put(qs.createKeyFor(index, q), bytes)
		if err != nil {
			return err
		}
	}
	return nil
}