写入后立即从 RavenDb 读取会返回不一致的数据
我有一个协调过程，其中后台线程定期从外部 Web 服务检索对象 ID 列表，并尝试将丢失的实体添加到嵌入式 RavenDb 数据库中。执行此过程的循环如下：
foreach (var pageId in listOfPageIds)
{
if ( _contentService.GetPageByPageId(pageId) == null)
{
_contentService.AddPage(pageId);
}
}
GetPageByPageId() 和 AddPage() 的实现如下：
public Page GetPageByPageId(string pageId)
{
using (var session = DocumentStore.OpenSession())
{
return session.Query<Page>().FirstOrDefault(page => page.PageId == pageId);
}
}
public bool AddPage(string pageId)
{
var page = GetPageByPageId(pageId);
if (page != null)
{
return false;
}
using (var session = DocumentStore.OpenSession())
{
var newPage = new Page() {PageId = pageId};
session.Store(newPage);
session.SaveChanges();
}
return true;
}
问题是，如果列表有重复的 id，一旦它添加第一个 id 并再次检查该 id，结果返回为空。就好像缺少注册新添加实体的最终确定步骤一样。如果我稍后从不同的线程查询该集合，则会返回具有给定 id 的实体。谁能看出这里有什么问题吗？
谢谢，
I have a reconciliation process where by a background thread that periodically retrieves a list of object ids from an external webservice and attempts to add the missing entities to an embedded RavenDb database. The loop that performs this process is the following:
foreach (var pageId in listOfPageIds)
{
if ( _contentService.GetPageByPageId(pageId) == null)
{
_contentService.AddPage(pageId);
}
}
the implementation of the GetPageByPageId() and AddPage() are as follows:
public Page GetPageByPageId(string pageId)
{
using (var session = DocumentStore.OpenSession())
{
return session.Query<Page>().FirstOrDefault(page => page.PageId == pageId);
}
}
public bool AddPage(string pageId)
{
var page = GetPageByPageId(pageId);
if (page != null)
{
return false;
}
using (var session = DocumentStore.OpenSession())
{
var newPage = new Page() {PageId = pageId};
session.Store(newPage);
session.SaveChanges();
}
return true;
}
The problem is that if the list has duplicate ids, once it adds the first id and checks for that id again, the result comes back as empty. It is as if a finalization step is missing that would register the newly added entity. If I query the set from a different thread at a later time, the entity with that given id is returned. Can anyone see what the issue is here?
thanks,
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这是Raven采用的最终一致性模型的结果。写入导致的索引更新是异步发生的，因此不久后执行读取可能会返回过时的结果。您可以更改查询以获得不陈旧的结果，如下所示：
还有一些其他选项Ayende这篇博文中涵盖了。
This is a result of the eventual consistency model that Raven adopts. Updates to the indexes as a result of writes happen asynchronously and therefore it is possible that performing a read shortly after will return stale results. You can alter your query to get non-stale results like this:
There's a couple of other options that Ayende covers in this blog post.