Question

我对这个问题的适当标题有问题，因为我有一个有趣的排序问题我想解决。

因此，我定义了3个user { skill: level }类型的对象：

a { s1: 1, s2: 2, s3: 4 }
b { s1: 2, s2: 2, s3: 4 }
c { s1: 1, s2: 5, s3: 9 }

现在，我想根据所选技能的总和对用户a，b和c进行排序。选择技能为s1和s2。我不关心s3。

过滤器[s1,s2]的有序结果应为[c,b,a]，因为

s1 + s2 for c = 6, 
            b = 4, 
            a = 3

我为这种情况定义了类：

class Skill
{
    public string Name { get; set; }
    public int Level { get; set; }
}

class User
{
    public string Name { get; set; }
    public IList<Skill> Skills { get; set; }            
}

并将其初始化：

var a = new User
            {
                    Name = "a",
                    Skills = new List<Skill>
                                {
                                    new Skill {Name = "s1", Level = 1},
                                    new Skill {Name = "s2", Level = 2},
                                    new Skill {Name = "s3", Level = 4}
                                }
                };
var b = new User
            {
                    Name = "b",
                    Skills = new List<Skill>
                                {
                                    new Skill {Name = "s1", Level = 2},
                                    new Skill {Name = "s2", Level = 2},                                              
                                    new Skill {Name = "s3", Level = 4}
                                }
                };
var c = new User
            {
                Name = "c",
                Skills = new List<Skill>
                                {
                                    new Skill {Name = "s1", Level = 1},
                                    new Skill {Name = "s2", Level = 5},
                                    new Skill {Name = "s3", Level = 9}
                                }
            };

下面我有用户列表和我想用于排序的技能列表：

var users = new List<User> {a, b, c};
var filters = new List<string> { "s1", "s2" };

我想收到

var selected = users.Magic(); // which results in [c,b,a]

我想用linq和ravendb这样做。显然我不想将数据库中的所有数据加载到内存中，然后进行魔术排序。我想我需要用map reduce创建一些疯狂的索引，然后对这些索引进行一些linq查询等等......帮忙？

顺便说一下：我正在使用RavenDB - Build＃960

修改

遗憾的是，我的临时解决方法是将所有用户数据读入内存并使用linq-to-objects（因为与raven linq驱动程序相关的问题，在查询期间不支持计算）：

var selected = users.OrderByDescending(user =>
                                user.Skills
                                    .Where(skill => filters.Contains(skill.Name))
                                    .Select(skill => skill.Level)
                                    .Sum());

Answer 1

var query = users.OrderBy(user => 
    user.Skills
    .Where(skill => skill.Name == "s1" || skill.Name == "s2")
    .Select(skill => skill.Level)
    .Sum());

Answer 2

创建一个索引，在索引时执行此求和并公开结果

from user in docs.Users
select new
{
    Skills_Sum = user.Skills.Sum(x=>x.Level)
}

使用LINQ和RavenDB对预定义过滤器进行嵌套排序

2 个答案: