Deiphobus, no more SELECT n + 1
Posted on August 04, 2011 ·
1 min read
· tagged with: #Cassandra #performance
This post has been imported from my previous blog. I did my best to parse XML properly, but it might have some errors.
If you find one, send a Pull Request.
The previous post contained an information about lazy loading of group of properties, let’s call them families as it is called in the Cassandra. What about the following code. How many db hits you’d like to get by default?
[sourcecode language=”csharp” light=”true”]
using (var s = sessionFactory.Open())
{
var user = s.Load(5);
foreach(var post in user.Posts)
{
Console.WriteLine(post.Title);
}
}
```
I'll tell you how many you'll get. The an
swer is two: first hit will occur, when a collection of posts is accessed in the *foreach* loop, the second - when a title is printed on the console. During the second hit all the posts loaded in the session will have their titles loaded. In some cases it may drive to a small overhead, but it simplifies batching and working with your entities in the majority of cases. Would anyone like to set *FetchMode*, like it was done in the NHibernate? ;)
