[英]Model one to many in RavenDb for better performance
I'm approaching to document database and I'm little bit confused how to map documents relationship, in a situation as follow 我正在接近文档数据库,但在以下情况下我有点困惑如何映射文档关系
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;}
}
A person has one or more cars for example in this way I can query the db as follow 例如,一个人以这种方式拥有一辆或多辆汽车,我可以如下查询数据库
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;
}
and it's everything ok, the client makes just one request, but if I have a person and I want to show all his cars how can I query the db to do just a request? 一切正常,客户端只提出一个请求,但是如果我有一个人,并且想向他展示他的所有汽车,我如何查询数据库以仅做一个请求? I think tha I must modify the model putting a
List<int> Cars
in Person
for reference his cars. 我认为我必须修改模型以放置
List<int> Cars
in Person
以供参考。 Note that I don't want to embed Cars
in the Person
document because Cars
can be referenced from others document. 请注意,我不想在“
Person
文档中嵌入“ Cars
,因为可以从其他文档中引用“ Cars
。
Thanks. 谢谢。
You can index the Cars collection and load all the cars from the index. 您可以为Cars集合建立索引,并从索引中加载所有汽车。
The index would look like this: 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,
};
}
}
The CarView class is identical to the Car class, but can be changed to better fit the indexing needs. CarView类与Car类相同,但是可以更改以更好地满足索引需求。
public class CarView
{
public int Id { get; set; }
public string Name { get; set; }
public int PersonId { get; set; }
}
You'll need to execute the index before being able to use it: 您需要先执行索引才能使用它:
new CarIndex().Execute(store);
Loading the cars for a certain person would look like this: 为某人装车看起来像这样:
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());
}
If you want to load the person and their cars in a single database request, use lazy loading: 如果要在单个数据库请求中加载人员及其汽车,请使用延迟加载:
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;
Complete test (needs xunit and RavenDB.Tests.Helpers nugets): 完整测试(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; }
}
}
You can do it like this: 您可以这样做:
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");
}
This make just a single db request. 这仅发出一个数据库请求。
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