在检查Contains方法中的过滤器文本时，Linq查询的性能问题

Question

我正在尝试执行下面的Linq查询，但问题是当我使用搜索查询文本在Linq查询下执行时，我一直在获取sql超时。请建议更好的方法来优化这一点。我的Db表有近50万条记录。

{
            QueryBuilder = (from ub in idamDbContext.UserBasicInfo
                            join ur in idamDbContext.UserRoles on ub.UserId equals ur.UserBasicInfoId
                            join r in idamDbContext.Role on ur.RoleId equals r.Id
                            join urt in idamDbContext.UserType on r.UserTypeId equals urt.Id
                            where (r.UserTypeId == 1 || r.UserTypeId == 3 || r.UserTypeId == 2) &&
                            (territoryId == null || ub.TerritoryId == territoryId) &&
                            (centerId == null || ub.CenterId == centerId) &&
                            (isActive == null || ub.IsActive == isActive)
                            orderby ub.Created
                            select new UserProfileDTO
                            {
                                UserId = ub.UserId,
                                UserName = ub.UserName,
                                FirstName = ub.FirstName,
                                LastName = ub.LastName,
                                Email = ub.Email,
                                TerritoryId = ub.TerritoryId,
                                UserTypeId = r.UserTypeId,
                                Description = r.Description,
                                Name = urt.Name
                            }
                   );

            if (!string.IsNullOrEmpty(query))
                QueryBuilder = QueryBuilder.Where(x => (!string.IsNullOrEmpty(x.FirstName) && x.FirstName.ToLower().Contains(query)) ||
                (!string.IsNullOrEmpty(x.LastName) && x.LastName.ToLower().Contains(query)) ||
                (!string.IsNullOrEmpty(x.Email) && x.Email.ToLower().Contains(query)) ||
                (!string.IsNullOrEmpty(x.Description) && x.Description.ToLower().Contains(query)) ||
                (!string.IsNullOrEmpty(x.UserName) && x.UserName.ToLower().Contains(query)) ||
                (!string.IsNullOrEmpty(x.Name) && x.Name.ToLower().Contains(query))
                );
        }