Yyds dry inventory ravendb start client API (III)

Delete()

We can go through Delete Method to delete a document , This method accepts instance entities or documents ID. The following code is the method of deleting documents ：

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var task = session.Load<ToDoTask>("ToDoTasks/1-A");
session.Delete(task); // delete by instance
session.Delete("ToDoTasks/1-A"); // delete by ID

     

      
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Bite here ,Delete Method does not delete the document , Just mark the document as deleted in the session , Only when calling SaveChanges Method document will be deleted .

Query()

In most cases, we will use view , Some query codes have been shown in this topic , Therefore, the query code is no longer listed in this section . And through the Load Call the loaded document , adopt Query The loaded document is also managed by the session . After we modify or delete the document , You also need to call SaveChanges Method to update RavenDB, And use Query There is only one instance of the queried document in the session , No matter how many times you check . Pay attention here RavenDB Calculation during query is not allowed （ for example ：SUM、AVG Such calculations ）, And it doesn't have the problem of table scanning or slow query . We will explain the reason in detail and introduce the detailed information about the index in the third part , But now you can see that most queries are suitable for you .

Store()

Store The method is to associate the entity with the session . We only do this when we want to create a new document . The case code is as follows ：

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var person = new Person
{
    Name = "Oscar Arava"    
};
session.Store(person);

     

      
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Again , And Delete The method is the same , Only when calling SaveChanges After the method , Data will be really saved in RavenDB in , And for the new ,RavenDB Will provide a ID. In addition to preserving the new body ,Store You can also associate existing document entities with sessions , This situation is generally used when the service weapon sends entities to the client , The client modifies the entity and sends it back Web Applications . But at this time, it was found that it was not loaded by the session nor tracked . Then you can call Store Method to bind entities and sessions , And its ID It's not empty ,RavenDB Think it exists in the Library , Therefore, it will be stored in the library in the form of updates .

SaveChanges()

SaveChanges Method is used to check all deleted and changed session States , Then send these to the server as a transaction , Therefore, this ensures that partial saving will not fail because of exceptions in the middle . call SaveChanges When the method is used , The entity loaded in the database and the current entity will be checked for changes . If there is a change , Then the entity will be saved to the database . The code is as follows ：

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using (var session = documentStore.OpenSession())
{
    // do some work with the session

    session.SaveChanges();
}

     

      
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Advanced

Ahead API Are common scenes , But there must be some unusual scenes , We can use Advanced To solve . For example, we can use it to configure optimistic concurrent behavior on a per session basis ：

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session.Advanced.UseOptimisticConcurrency = true;

     

      
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You can also modify the Convention to globally define ：

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documentStore.Conventions.UseOptimisticConcurrency = true;

     

      
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I will explain the specific content in the following topics .