我需要将linq查询转换为NEST。那就是我的linq查询的样子:

var result = studentList
            .GroupBy(student => student.Name)
            .Select(group => group.OrderByDescending(student => student.grade).Take(3))
            .SelectMany(p => p);

这应该:
  • 按学生名字分类
  • 按等级对每个组逐个排序,
  • 降序
  • 从每个组中选出成绩最好的X名前学生

  • 它与linq一起工作,但是如何使用NEST做到这一点?
    我正在尝试聚合,子聚合,分类存储桶,但没有成功。

    我知道如何按名称分组,但是接下来呢?
    client.Search<Students>(s => s
    .Aggregations(a => a
        .Terms("group_by_name", ts => ts
            .Field(o => o.Name))));
    

    如何订购每个小组,如何从每个小组中选拔顶尖学生?

    最佳答案

    假设模型像

    public class Student
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Grade { get; set; }
    }
    

    以下将按学生姓名分组,然后按成绩降序获得各组中的热门x命中值
    private static void Main()
    {
        var defaultIndex = "students";
        var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));
    
        var settings = new ConnectionSettings(pool)
            .DefaultIndex(defaultIndex);
    
        var client = new ElasticClient(settings);
    
        if (client.IndexExists(defaultIndex).Exists)
            client.DeleteIndex(defaultIndex);
    
        var createIndexResponse = client.CreateIndex(defaultIndex, c => c
            .Settings(s => s
                .NumberOfShards(1)
                .NumberOfReplicas(0)
            )
            .Mappings(m => m
                .Map<Student>(mm => mm
                    .AutoMap()
                )
            )
        );
    
        var students = Enumerable.Range(1, 20).Select(i =>
            new Student
            {
                Id = i,
                Name = i % 2 == 0 ? "Foo" : "Bar",
                Grade = i
            }
        );
    
        var bulkResponse = client.Bulk(b => b
            .IndexMany(students)
            .Refresh(Refresh.WaitFor) // refresh, so that documents indexed are available to search immediately
        );
    
        var topX = 10;
    
        var searchResponse = client.Search<Student>(s => s
            .Aggregations(a => a
                .Terms("student_name", t => t
                    .Field(f => f.Name.Suffix("keyword"))
                    .Aggregations(aa => aa
                        .TopHits("top_grades", th => th
                            .Sort(so => so
                                .Descending(f => f.Grade)
                            )
                            .Size(topX)
                        )
                    )
                )
            )
        );
    
        var studentNames = searchResponse.Aggregations.Terms("student_name");
    
        foreach(var bucket in studentNames.Buckets)
        {
            var header = $"Student Name: {bucket.Key}";
            Console.WriteLine(header);
            Console.WriteLine(new string('-', header.Length));
            foreach(var hit in bucket.TopHits("top_grades").Documents<Student>())
            {
                Console.WriteLine($"Id: {hit.Id}, Grade: {hit.Grade}");
            }
            Console.WriteLine();
        }
    }
    

    打印出来
    Student Name: Bar
    -----------------
    Id: 19, Grade: 19
    Id: 17, Grade: 17
    Id: 15, Grade: 15
    Id: 13, Grade: 13
    Id: 11, Grade: 11
    Id: 9, Grade: 9
    Id: 7, Grade: 7
    Id: 5, Grade: 5
    Id: 3, Grade: 3
    Id: 1, Grade: 1
    
    Student Name: Foo
    -----------------
    Id: 20, Grade: 20
    Id: 18, Grade: 18
    Id: 16, Grade: 16
    Id: 14, Grade: 14
    Id: 12, Grade: 12
    Id: 10, Grade: 10
    Id: 8, Grade: 8
    Id: 6, Grade: 6
    Id: 4, Grade: 4
    Id: 2, Grade: 2
    

    关于c# - ElasticSearch NEST-先按GroupBy再按OrderBy,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/54491500/

    10-13 06:11