技术专家

在上一节当中已经介绍了RavenDb的文档设计模式，这一节我们要具体讲一讲如何使用api去访问RavenDb

1.连接RavenDb



var documentStore = new DocumentStore { Url = "http://myravendb.mydomain.com/" };

documentStore.Initialize();



var documentStore = new DocumentStore

{

ConnectionStringName = "MyRavenConStr"

};

在app.config中配置如下：

<connectionStrings>

<add name="Local" connectionString="DataDir = ~\Data"/>

<add name="Server" connectionString="Url = http://localhost:8080"/>

<add name="Secure" connectionString="Url = http://localhost:8080;user=beam;password=up;ResourceManagerId=d5723e19-92ad-4531-adad-8611e6e05c8a"/>

</connectionStrings>



参数：

DataDir - embedded mode的参数, 只能实例化一个EmbeddableDocumentStore,

Url -  server mode的参数

User / Password - server mode的参数

Enlist - whatever RavenDB should enlist in distributed transactions. 不适合Silverlight

ResourceManagerId - 可选的, server mode的参数, the Resource Manager Id that will be used by the Distributed Transaction Coordinator (DTC) service to identify Raven. A custom resource manager id will need to be configured for each Raven server instance when Raven is hosted more than once per machine.不适合Silverlight

Database - server mode的参数,不是用内置的数据库

Url的方式：

Url = http://ravendb.mydomain.com
connect to a remote RavenDB instance at ravendb.mydomain.com, to the default database
Url = http://ravendb.mydomain.com;Database=Northwind
connect to a remote RavenDB instance at ravendb.mydomain.com, to the Northwind database there
Url = http://ravendb.mydomain.com;User=user;Password=secret
connect to a remote RavenDB instance at ravendb.mydomain.com, with the specified credentials
DataDir = ~\App_Data\RavenDB;Enlist=False 
use embedded mode with the database located in the App_Data\RavenDB folder, without DTC support.
2.Session使用案例
//写入
string companyId;

using (var session = documentStore.OpenSession())

{

    var entity = new Company { Name = "Company" };

    session.Store(entity);

    session.SaveChanges();

    companyId = entity.Id;

}

//读取

using (var session = documentStore.OpenSession())

{

    var entity = session.Load<Company>(companyId);

    Console.WriteLine(entity.Name);

}

//删除,一旦删除无法恢复

using (var session = documentStore.OpenSession())

{

session.Delete(existingBlogPost);

session.SaveChanges();

}

下面两种方式也可以删除 session.Advanced.Defer(new DeleteCommandData { Key = "posts/1234" });

session.Advanced.DocumentStore.DatabaseCommands.Delete("posts/1234", null);



3.查询

//PageSize

如果没有设置PageSize，客户端调用是一次128条记录，服务端调用是一次1024条记录，远程调用是一次30条记录，可以配置。

RavenDb为了加快查询数据的速度，它在后台使用的是lucene的索引方式，通过linq来生成HTTP RESTful API。

//查询,用linq的方式查询很方便

var results = from blog in session.Query<BlogPost>()

              where blog.Category == "RavenDB"

              select blog;

var results = session.Query<BlogPost>()

    .Where(x => x.Comments.Length >= 10)

    .ToList();



//分页查询

var results = session.Query<BlogPost>()

    .Skip(20) // skip 2 pages worth of posts

    .Take(10) // Take posts in the page size

    .ToArray(); // execute the query



//分页的时候，我们一次取10条，但是我们也要知道总共有多少条数据，我们需要通过TotalResults来获得

RavenQueryStatistics stats;

var results = session.Query<BlogPost>()

    .Statistics(out stats)

    .Where(x => x.Category == "RavenDB")

    .Take(10)

    .ToArray();

var totalResults = stats.TotalResults;



//跳过指定的临时的数据集，每次查询都记录下上一次查询记录的跳过的查询记录，该值保存在SkippedResults

RavenQueryStatistics stats;

// get the first page

var results = session.Query<BlogPost>()

    .Statistics(out stats)

    .Skip( * 10) // retrieve results for the first page

    .Take(10) // page size is 10

    .Where(x => x.Category == "RavenDB")

    .Distinct()

    .ToArray();

var totalResults = stats.TotalResults;

var skippedResults = stats.SkippedResults;

 

// get the second page

results = session.Query<BlogPost>()

    .Statistics(out stats)

    .Skip((1 * 10) + skippedResults) // retrieve results for the second page, taking into account skipped results

    .Take(10) // page size is 10

    .Where(x => x.Category == "RavenDB")

    .Distinct()

    .ToArray();

//查询出来的数据不一定是新的,如果stats.IsStale不为true的话，它就报错的啦

if (stats.IsStale)

{

    // Results are known to be stale

}



//设定获取时间，更新时间截止到某个时刻

RavenQueryStatistics stats;

var results = session.Query<Product>()

    .Statistics(out stats)

    .Where(x => x.Price > 10)

    .Customize(x => x.WaitForNonStaleResultsAsOf(new DateTime(2011, 5, 1, 10, , , )))

    .ToArray();



//设置查询返回后一次更新 documentStore.Conventions.DefaultQueryingConsistency = ConsistencyOptions.QueryYourWrites;