如何在RavenDB中查询嵌套信息？

Question

我有以下文件叫做预订:

{
    "CustomerId": 1,
    "Items": [
        {
            "EmployeeId": "employees/1",
            "StartTime": "2011-08-15T07:20:00.0000000+03:00",
            "EndTime": "2011-08-15T07:40:00.0000000+03:00"
        },
        {
            "EmployeeId": "employees/1",
            "StartTime": "2011-08-15T07:40:00.0000000+03:00",
            "EndTime": "2011-08-15T09:10:00.0000000+03:00"
        },
        {
            "EmployeeId": "employees/3",
            "StartTime": "2011-08-16T07:20:00.0000000+03:00",
            "EndTime": "2011-08-16T11:35:00.0000000+03:00"
        }
    ]
    "ReservedAt": "2011-10-20T15:28:21.9941878+03:00"
}

另外我有以下投影类:

public class ReservationItemProjection
{
    public string ReservationId { get; set; }
    public string CustomerId { get; set; }
    public string EmployeeId { get; set; }
    public DateTime StartTime { get; set; }
    public DateTime EndTime { get; set; }
}

如果我想找到匹配的ReservationItemProjections,我会写什么样的索引和查询？例如:

// invalid example query:
var matches = docs.Query<ReservationItemProjection,
    ReservationItemProjectionsIndex>()
    .Where(x =>
        x.EmployeeId == "employees/1" &&
        x.StartTime >= minTime &&
        x.EndTime <= maxTime)
    .ToList();

请注意,我不希望获得Reservation文档列表,而是获取ReservationItemProjection对象列表.该文件说:

但是,只是获取匹配特定查询的文档是有用的,我们可以做得更好.我想直接从索引中获取值而不是获取完整的文档,而不是自己获取文档.

我已经尝试使用这样的索引:

public class ReservationItemProjectionsIndex : 
    AbstractIndexCreationTask<Reservation, ReservationItemProjection>
{
    public ReservationItemProjectionsIndex()
    {
        Map = reservations => 
            from reservation in reservations
            from item in reservation.Items
            select new
            {
                ReservationId = reservation.Id,
                CustomerId = reservation.CustomerId,
                item.EmployeeId,
                item.StartTime,
                item.EndTime
            };
        Store(x => x.ReservationId, FieldStorage.Yes);
        Store(x => x.CustomerId, FieldStorage.Yes);
        Store(x => x.EmployeeId, FieldStorage.Yes);
        Store(x => x.StartTime, FieldStorage.Yes);
        Store(x => x.EndTime, FieldStorage.Yes);
    }
}

不知怎的,我无法使查询和索引工作:它抛出一个异常,关于无法从ReservationItemProjection转换为Reservation,或者当我能够获取ReservationItemProjection对象时,它们将包含所有预留中的所有项目甚至有一个匹配的项目,即使我的查询具有Where子句x.EmployeeId =="employees/1".

总结:所需索引是什么？索引是仅需要Map子句还是Reduce或TransformResults？如何在C#中编写查询？

Answer 1

Kasper,在RavenDB中,您正在查询文档.虽然技术上可以做你想做的事情,但这样做通常没有意义,因为预测的信息没有必要的上下文来做它.

你想做什么？

作为参考,索引将是这样的:

 from doc in docs.Items
 from reservation in doc.Reservations
 select new { reservation.EmployeeId, reservation.Start, reservation.End }

然后,将EmployeeId,Start和End标记为Store.

现在,在您的查询中,发出:

  session.Query<...,...>().AsProjection<ReservationProjection>().ToList();

AsProjection调用将让DB知道您想要索引的值,而不是文档