Where a category can have multiple topics and each of those topics can have multiple posts, just like this forum. When I list the categories I am showing the last post within a category and came up with this method.
Is there a better way of doing this? Obviously I am looking for as big a performance increases I can from any change
public ForumPost GetLastPostInCategory(List<ForumTopic> topics)
{
// Get latest Post (Must be a more efficient way of doing this in linq!)
var posts = new List<ForumPost>();
foreach (var topic in topics)
{
posts.AddRange(topic.ForumPosts);
}
// Setup local variables to use
return lpost = posts.OrderByDescending(x => x.CreateDate).First();
}
I had been looking at it myself because I was in a similar situation where using "order" or "orderby" might have a performance implication due to the number of items in a list. So I have been doing some unit tests similar to the benchmarks in the post above, and the following method is the fastest (rewritten to match your sample code):
public ForumPost GetLastPostInCategory(List<Topic> topics) { ForumPost newestPost = topics[0].ForumPosts[0];//Assumes no empty lists foreach (var topic in topics) { foreach (var post in topic.ForumPosts) { if (post.CreateDate > newestPost.CreateDate) { newestPost = post; } } }
return newestPost; }
Result was 45ms with a list of 10.000 topics each containing 1000 posts. Best result using LINQ (and Extension method) was 67ms. I tried running your sample code as well, which gave a result of 5sec 12ms, so you are looking at quite a performance enhancement dropping the OrderBy - and no need to create a new list with all your forum posts if you are only going to return the latest post.
Morton thanks for taking the time to look into this :) Really appreciate it, and the results are just what I was looking for. Only one issue I have though, when I try to do this I get the following error??
Actually, while we are still on this subject :P My next task is to find an efficient way of doing the same thing, but ordering the topics listing in a category by the latest post. The code I currently have is this, which just uses the default sort order
var maintopics = from t in u.ForumTopics
where t.ParentNodeId == CurrentNode.Id
orderby t.SortOrder descending
select t;
But this isn't right, as if someone posts in the bottom topic I want it to be at the top not stay at the bottom - I'm going to have a play and post what I come up with back here... But if you have any suggestions I'd be happy to see/hear them :)
Linq2Umbraco Performance Help
I have the following structure
Category
-- Topic
-- Post
Where a category can have multiple topics and each of those topics can have multiple posts, just like this forum. When I list the categories I am showing the last post within a category and came up with this method.
Is there a better way of doing this? Obviously I am looking for as big a performance increases I can from any change
public ForumPost GetLastPostInCategory(List<ForumTopic> topics) { // Get latest Post (Must be a more efficient way of doing this in linq!) var posts = new List<ForumPost>(); foreach (var topic in topics) { posts.AddRange(topic.ForumPosts); } // Setup local variables to use return lpost = posts.OrderByDescending(x => x.CreateDate).First(); }Any advice/tips greatly appreciated.
Hi Lee,
I don't know the exact code but can't you do something along
var posts = from p in [YourDataContext].ForumPosts
where p.CreateDate == [MAX(p.CreateDate)] //don't know if that is possible here but would make it quite a lot better. Maybe it's worth even
//running an additional query beforehand just to get the latest date?
orderby p.CreateDate;
if (posts.Count > 0) { posts = posts.First(); }
? Hth, Sascha
Thanks for the tips, I'll see what I can incorporate into it :)
Hi Lee,
This is an interesting "issue", and I have already sent you the link to a post by Jon Skeet about LINQ Performance:
http://msmvps.com/blogs/jon_skeet/archive/2005/10/02/a-short-case-study-in-linq-efficiency.aspx
I had been looking at it myself because I was in a similar situation where using "order" or "orderby" might have a performance implication due to the number of items in a list. So I have been doing some unit tests similar to the benchmarks in the post above, and the following method is the fastest (rewritten to match your sample code):
Result was 45ms with a list of 10.000 topics each containing 1000 posts. Best result using LINQ (and Extension method) was 67ms. I tried running your sample code as well, which gave a result of 5sec 12ms, so you are looking at quite a performance enhancement dropping the OrderBy - and no need to create a new list with all your forum posts if you are only going to return the latest post.
- Morten
Morten thanks for posting this. Really helped me out.
Morton thanks for taking the time to look into this :) Really appreciate it, and the results are just what I was looking for. Only one issue I have though, when I try to do this I get the following error??
Ignore me, its early :P Just sorted it with
Morten out of interest what do you use for your Unit Tests?
Actually, while we are still on this subject :P My next task is to find an efficient way of doing the same thing, but ordering the topics listing in a category by the latest post. The code I currently have is this, which just uses the default sort order
var maintopics = from t in u.ForumTopics where t.ParentNodeId == CurrentNode.Id orderby t.SortOrder descending select t;But this isn't right, as if someone posts in the bottom topic I want it to be at the top not stay at the bottom - I'm going to have a play and post what I come up with back here... But if you have any suggestions I'd be happy to see/hear them :)
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