A few days ago a friend emailed me the following question regarding NHibernate mappings for a solution he’s currently developing:
“I have an idea entity that has a collection of comment entities and I need to get the comment count for each idea. I made a massive mistake at the beginning by calling idea.Comments.Count (even worse, I did it in the view!), which due to the collection being lazy-loaded caused about 10 database calls so performance was sluggish even with second level cache. I was therefore wondering how you would do it - would you use HQL and use Comments.size or would you do something differently?”
Now, I’ve been pretty busy recently, so before I had opportunity to respond properly, he sent this follow-up:
"After looking for a solution for getting a Comment count back for each Idea, I found using the Nhibernate Formula method does the job - just wanting to make sure I was on the right track in terms of performance etc. My mapping class is as follows:"
public class IdeaMap : ClassMap<Idea>
{}
}
Read more:
Ian Nelson
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