[英]Model one to many in RavenDb for better performance
我正在接近文檔數據庫,但在以下情況下我有點困惑如何映射文檔關系
public class Person
{
public Person()
{
}
public int Id { get; set; }
public string Name { get;set;}
public string Surname { get; set; }
public DateTime? BirthDate { get; set; }
}
public class Car
{
public Car() { }
public int Id { get; set; }
public string Name { get; set; }
public int PersonId { get; set;}
}
例如,一個人以這種方式擁有一輛或多輛汽車,我可以如下查詢數據庫
public Car Get(int id)
{
Car car = null;
using (IDocumentSession session = store.OpenSession())
{
car = session.Include<Car, Person>(x => x.PersonId).Load<Car>(id);
bool isLoaded = session.Advanced.IsLoaded("people/" + car.PersonId); // true!
}
return car;
}
一切正常,客戶端只提出一個請求,但是如果我有一個人,並且想向他展示他的所有汽車,我如何查詢數據庫以僅做一個請求? 我認為我必須修改模型以放置List<int> Cars
in Person
以供參考。 請注意,我不想在“ Person
文檔中嵌入“ Cars
,因為可以從其他文檔中引用“ Cars
。
謝謝。
您可以為Cars集合建立索引,並從索引中加載所有汽車。
索引如下所示:
public class CarIndex : AbstractIndexCreationTask<Car, CarView>
{
public CarIndex()
{
Map = cars => from car in cars
select new
{
car.Id,
car.Name,
car.PersonId,
};
}
}
CarView類與Car類相同,但是可以更改以更好地滿足索引需求。
public class CarView
{
public int Id { get; set; }
public string Name { get; set; }
public int PersonId { get; set; }
}
您需要先執行索引才能使用它:
new CarIndex().Execute(store);
為某人裝車看起來像這樣:
using (IDocumentSession session = store.OpenSession())
{
session.Store(new Person { Id = 1, Name = "A", Surname = "A" });
session.Store(new Car { Id = 1, Name = "A", PersonId = 1 });
session.Store(new Car { Id = 2, Name = "B", PersonId = 1 });
session.Store(new Car { Id = 3, Name = "C", PersonId = 2 });
session.SaveChanges();
}
WaitForIndexing(store); // from RavenTestBase
using (IDocumentSession session = store.OpenSession())
{
var resultsForId1 = session
.Query<CarView, CarIndex>()
.ProjectFromIndexFieldsInto<CarView>()
.Where(x => x.PersonId == 1);
Assert.Equal(2, resultsForId1.Count());
var resultsForId2 = session
.Query<CarView, CarIndex>()
.ProjectFromIndexFieldsInto<CarView>()
.Where(x => x.PersonId == 2);
Assert.Equal(1, resultsForId2.Count());
}
如果要在單個數據庫請求中加載人員及其汽車,請使用延遲加載:
var resultsForId1 = session
.Query<CarView, CarIndex>()
.ProjectFromIndexFieldsInto<CarView>()
.Where(x => x.PersonId == 1).Lazily();
var person = session.Advanced.Lazily.Load<Person>(1);
var personValue = person.Value;
var resultsValue = resultsForId1.Value;
完整測試(需要xunit和RavenDB.Tests.Helpers nugets):
using Raven.Client;
using Raven.Client.Indexes;
using Raven.Tests.Helpers;
using System;
using System.Linq;
using Xunit;
namespace SO41547501Answer
{
public class SO41547501 : RavenTestBase
{
[Fact]
public void SO41547501Test()
{
using (var server = GetNewServer())
using (var store = NewRemoteDocumentStore(ravenDbServer: server))
{
new CarIndex().Execute(store);
using (IDocumentSession session = store.OpenSession())
{
session.Store(new Person { Id = 1, Name = "A", Surname = "A" });
session.Store(new Car { Id = 1, Name = "A", PersonId = 1 });
session.Store(new Car { Id = 2, Name = "B", PersonId = 1 });
session.Store(new Car { Id = 3, Name = "C", PersonId = 2 });
session.SaveChanges();
}
WaitForAllRequestsToComplete(server);
WaitForIndexing(store);
using (IDocumentSession session = store.OpenSession())
{
var resultsForId1 = session
.Query<CarView, CarIndex>()
.ProjectFromIndexFieldsInto<CarView>()
.Where(x => x.PersonId == 1);
Assert.Equal(2, resultsForId1.Count());
var resultsForId2 = session
.Query<CarView, CarIndex>()
.ProjectFromIndexFieldsInto<CarView>()
.Where(x => x.PersonId == 2);
Assert.Equal(1, resultsForId2.Count());
}
using (IDocumentSession session = store.OpenSession())
{
server.Server.ResetNumberOfRequests();
var resultsForId1 = session
.Query<CarView, CarIndex>()
.ProjectFromIndexFieldsInto<CarView>()
.Where(x => x.PersonId == 1).Lazily();
var person = session.Advanced.Lazily.Load<Person>(1);
var personValue = person.Value;
var resultsValue = resultsForId1.Value;
Assert.Equal("A", personValue.Name); // person data loaded
Assert.Equal("A", resultsValue.First().Name); // cars data loaded
Assert.Equal(1, server.Server.NumberOfRequests); // only one request sent to the server
}
}
}
}
public class CarIndex : AbstractIndexCreationTask<Car, CarView>
{
public CarIndex()
{
Map = cars => from car in cars
select new
{
car.Id,
car.Name,
car.PersonId,
};
}
}
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
public string Surname { get; set; }
public DateTime? BirthDate { get; set; }
}
public class Car
{
public int Id { get; set; }
public string Name { get; set; }
public int PersonId { get; set; }
}
public class CarView
{
public int Id { get; set; }
public string Name { get; set; }
public int PersonId { get; set; }
}
}
您可以這樣做:
using (IDocumentSession session = store.OpenSession())
{
var carsForOne = session.Query<Car>()
.Include(x=>x.PersonId)
.Where(x=>x.PersonId == "people/1")
.ToList();
var person = session.Load<Person>("people/1");
}
這僅發出一個數據庫請求。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.