Comments on: Improve LINQ Query Performance

By: fdumlao

fdumlao — Sat, 18 Apr 2009 01:35:21 +0000

Essentially what you were looking for here was the difference of two collections (myTasks and outlookTasks). Enumerable has a built in method (Except()) to handle these when the collections are of the same type, and LINQ adds the ability to pass in a query to the "Except" method so that you can transform one collection before it is used.

Your first approach was O(N^2), iterating over one collection then iterating over the second collection once for each iteration of the first collection.

Your second approach is better: O(N) + O(N), which will iterate through collection one, then collection 2. However as the collections get bigger this will begin to take longer, which an optimized intersect algorithm can help you to avoid!

if you instead used:

Dim results = _
myTasks.Except(From outlookTask In outlookTasks _
Select outlookTask.Subject)

which I believe is implemented as O(N log N) which should nicely plateau and provide reliable performance even as the collections get larger, not to mention fewer lines of code!

Hope this helped!

By: fdumlao

fdumlao — Fri, 17 Apr 2009 18:35:21 +0000

By: aquiaqui

aquiaqui — Fri, 06 Feb 2009 16:02:36 +0000

thanks!

By: Emad Ibrahim

Emad Ibrahim — Thu, 06 Mar 2008 15:08:58 +0000

Ed, thanks for the tip, I will give it a shot and report back.

By: Emad Ibrahim

Emad Ibrahim — Thu, 06 Mar 2008 12:08:58 +0000

Ed, thanks for the tip, I will give it a shot and report back.

By: Ed Richard

Ed Richard — Thu, 06 Mar 2008 10:05:42 +0000

I’m wondering Emad, have you considered optimizing using the new GetTable method on the folder class?

By: Ed Richard

Ed Richard — Thu, 06 Mar 2008 07:05:42 +0000

I’m wondering Emad, have you considered optimizing using the new GetTable method on the folder class?