Function verifyUnique

edgraph/server.go:1776–1861

verifyUnique verifies uniqueness of mutation

(qc *queryContext, qr query.Request)

// verifyUnique verifies uniqueness of mutation
func verifyUnique(qc *queryContext, qr query.Request) error {
	if len(qc.uniqueVars) == 0 {
		return nil
	}

	for i, queryVar := range qc.uniqueVars {
		gmuIndex, rdfIndex := decodeIndex(i)
		pred := qc.gmuList[gmuIndex].Set[rdfIndex]
		queryResult := qr.Vars[queryVar.queryVar]
		if !isUpsertCondTrue(qc, int(gmuIndex)) {
			continue
		}
		isEmpty := func(l *pb.List) bool {
			return l == nil || len(l.Uids) == 0
		}

		var subjectUid uint64
		if strings.HasPrefix(pred.Subject, "uid(") {
			varName := qr.Vars[pred.Subject[4:len(pred.Subject)-1]]
			if isEmpty(varName.Uids) {
				subjectUid = 0 // blank node
			} else if len(varName.Uids.Uids) == 1 {
				subjectUid = varName.Uids.Uids[0]
			} else {
				return errors.Errorf("unique constraint violated for predicate [%v]", pred.Predicate)
			}
		} else {
			var err error
			subjectUid, err = parseSubject(pred.Subject)
			if err != nil {
				return errors.Wrapf(err, "error while parsing [%v]", pred.Subject)
			}
		}

		var predValue interface{}
		if strings.HasPrefix(pred.ObjectId, "val(") {
			varName := qr.Vars[pred.ObjectId[4:len(pred.ObjectId)-1]]
			val, ok := varName.Vals.Get(0)
			if !ok {
				_, isValueGoingtoSet := varName.Vals.Get(subjectUid)
				if !isValueGoingtoSet {
					continue
				}

				results := qr.Vars[queryVar.valVar]
				err := results.Vals.Iterate(func(uidOfv uint64, v types.Val) error {
					varNameVal, _ := varName.Vals.Get(subjectUid)
					if v.Value == varNameVal.Value && uidOfv != subjectUid {
						return errors.Errorf("could not insert duplicate value [%v] for predicate [%v]",
							v.Value, pred.Predicate)
					}
					return nil
				})
				if err != nil {
					return err
				}
				continue
			} else {