UID query response shows bad data + data type

[jostillmanns]

Describe the bug

Given a non-list relation hostType->nestingType, when updating that relation multiple times, the query response for the relation starts to give bad results. The result type for uid is a list of uids and uids internal to that list are previous relationships of hostType->nestingType

Example Query response: {"result":[{"uid":"0x53","nestingType":{"uid":["0x4f","0x50"]}}]}

To Reproduce

Run this test:

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"reflect"
	"strconv"
	"testing"
	"time"

	"github.com/dgraph-io/dgo/v240"
	"github.com/dgraph-io/dgo/v240/protos/api"
	"github.com/stretchr/testify/require"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
)

func Test_it_correctly_yields_uid_field(t *testing.T) {
	conn, err := grpc.NewClient("localhost:9080", grpc.WithTransportCredentials(insecure.NewCredentials()))
	if err != nil {
		t.Fatalf("conntect: %v", err)
	}

	dgraphClient := dgo.NewDgraphClient(api.NewDgraphClient(conn))

	schema := `
type nestingType {
  nestingType.createdAt
}

type hostType {
  hostType.createdAt
  hostType.nestingType
}

nestingType.createdAt: dateTime .
hostType.createdAt: dateTime .
hostType.nestingType: uid @reverse .
`

	err = dgraphClient.Alter(context.Background(), &api.Operation{DropAll: true})
	require.NoError(t, err)

	err = dgraphClient.Alter(context.Background(), &api.Operation{Schema: schema})
	require.NoError(t, err)

	createCmd, err := json.Marshal([]map[string]any{
		{"dgraph.type": "nestingType", "uid": "_:probe0", "nestingType.createdAt": time.Time{}},
		{"dgraph.type": "nestingType", "uid": "_:probe1", "nestingType.createdAt": time.Time{}},
		{"dgraph.type": "nestingType", "uid": "_:probe2", "nestingType.createdAt": time.Time{}},
		{"dgraph.type": "nestingType", "uid": "_:probe3", "nestingType.createdAt": time.Time{}},
	})
	require.NoError(t, err)

	resp, err := dgraphClient.NewTxn().Mutate(context.Background(), &api.Mutation{SetJson: createCmd, CommitNow: true})
	require.NoError(t, err)

	uids := make([]uint64, 4)
	for i := range uids {
		var err error
		uids[i], err = strconv.ParseUint(resp.Uids[fmt.Sprintf("probe%d", i)], 0, 64)
		require.NoError(t, err)
	}

	createCmd, err = json.Marshal([]map[string]any{
		{"dgraph.type": "hostType", "hostType.createdAt": time.Time{}, "hostType.nestingType": map[string]any{"uid": uids[0]}, "uid": "_:probe"},
	})
	require.NoError(t, err)

	resp, err = dgraphClient.NewTxn().Mutate(context.Background(), &api.Mutation{SetJson: createCmd, CommitNow: true})
	require.NoError(t, err)

	hostTypeID := resp.Uids["probe"]

	for _, uid := range uids[1:] {
		txn := dgraphClient.NewTxn()

		q := `query { result(func: uid(%s)) { uid, nestingType: hostType.nestingType { uid }}}`

		queryResp, err := txn.Query(context.Background(), fmt.Sprintf(q, hostTypeID))
		require.NoError(t, err)

		var queryResponse map[string]any
		require.NoError(t, json.Unmarshal(queryResp.Json, &queryResponse))

		require.Equal(t, reflect.String, reflect.TypeOf(queryResponse["result"].([]any)[0].(map[string]any)["nestingType"].(map[string]any)["uid"]).Kind(), string(queryResp.Json))

		updateCmd, err := json.Marshal([]map[string]any{{
			"uid":                  hostTypeID,
			"hostType.nestingType": map[string]any{"uid": uid},
		}})
		require.NoError(t, err)

		_, err = txn.Mutate(context.Background(), &api.Mutation{SetJson: updateCmd})
		require.NoError(t, err)

		require.NoError(t, txn.Commit(context.Background()))
	}
}

Expected behavior

• require.Equal(t, reflect.String, reflect.TypeOf(queryResponse["result"].([]any)[0].(map[string]any)["nestingType"].(map[string]any)["uid"]).Kind(), string(queryResp.Json)) should never fail.
• query for uid should always be a string (hex value)
• query for uid should not yield non-valida data (uid for old relationships)

Environment

• Version: v24.1.2
• Alpha flags: dgraph alpha --zero dgx-testing-zero:5080 --security "whitelist=0.0.0.0/0" --my dgx-testing-alpha:7080
• Zero flags: zero --my=dgx-testing-zero:5080

Additional context

I discovered this issue when trying to migrate to v24.1.2 . We had seen this issue with v23 as well, but could never reproduce it. With v24 I am able to consistently reproduce the issue with the above test.

[linear[bot]]

DGR-887 UID query response shows bad data + data type

[xqqp]

This is similar to the issue described in https://discuss.hypermode.com/t/inconsistent-query-result/19844/8. A fix (https://github.com/hypermodeinc/dgraph/pull/9378) for this has been merged but has not been released yet. You can check if this fixes your problem by trying the nightly docker image or building from source.

[jostillmanns]

can confirm, that https://github.com/hypermodeinc/dgraph/pull/9378 fixes the issue 👍