问优化ef-core查询

EN

using (var session = new Typo3DBContext())
            {
                var countryList = session.TxNeustageodataDomainModelCountry
                            .Where(x => x.Deleted == 0)
                            .Join(session.TxNeustameinereiseDomainModelTripCountryMm,
                                    country => (uint)country.Uid,
                                    tripMM => tripMM.UidForeign,
                                    (country, tripMM) =>
                                        new
                                        {
                                            country = country,
                                            tripMM = tripMM
                                        })
                            .Join(session.TxNeustameinereiseDomainModelTrip,
                                    combinedEntry => combinedEntry.tripMM.UidLocal,
                                    trip => trip.Uid,
                                    (combinedEntry, trip) =>
                                        new
                                        {
                                            combinedEntry = combinedEntry,
                                            trip = trip
                                        })
                            .GroupBy(
                                temp =>
                                    new
                                    {
                                        Name = temp.combinedEntry.country.Name,
                                        Iso = temp.combinedEntry.country.Iso,
                                        Id = temp.combinedEntry.tripMM.UidForeign,
                                        Status = temp.trip.Status,
                                        Deleted = temp.trip.Deleted
                                    },
                                temp => temp.combinedEntry.tripMM
                            )
                            .Where(x => x.Key.Status == 2 && x.Key.Deleted == 0)
                            .Select(
                                group =>
                                    new CountryHelperClass
                                    {
                                        Count = group.Count(),
                                        Iso = group.Key.Iso,
                                        Name = group.Key.Name,
                                        Id = group.Key.Id

                                    })
                            .ToList();

                return countryList;
            }