indexing - 如何在 RavenDB 中查询嵌套信息？

Question

我有以下名为 Reservation 的文件:

{
    "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"
}

此外，我还有以下投影类:

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; }
}

如果我想找到匹配我写什么样的索引和查询
预订项目预测？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，我不希望获得预订文件 list ，而是希望获得一份
ReservationItemProjection 对象列表。 documentation说:

But while just getting the documents matching a particular query is useful, we can do better than that. Instead of getting the documents themselves, I want to get the values directly from the index, without getting the full document.

我已经尝试过使用这样的索引:

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);
    }
}

不知何故我无法让查询和索引工作:它要么抛出一个关于
无法从 ReservationItemProjection 转换为 Reservation 或者，当我
已经能够获得 ReservationItemProjection 对象，他们将有
包括所有预订中的所有项目，即使有一个匹配的项目，甚至
虽然我的查询有 Where-clause x.EmployeeId == "employees/1"。

摘要:所需的索引是什么？索引是否只需要 Map 子句或还需要 Reduce 或 TransformResults？如何在 C# 中编写查询？

Answer 1

卡斯帕，
在 RavenDB 中，您正在查询文档。虽然技术上可以做你想做的事，但这样做通常毫无意义，因为转换的信息没有必要的上下文来处理它。

你想要做什么？

作为引用，索引将类似于:

 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 知道您想要来自索引的值，而不是文档