Skip to main content

C#: LINQ and Foreach performance comparison

I'm currently solving performance issues we have programmed within the last milestone. A lot of bugs were already fixed but very interesting issue hasn't.

I have liked and preferred LINQ queries over simple foreach command. Mentioned performance issue was based on the following query.

Entity e = entities.Where(e => e.Id.Equals(id)).FirstOrDefault();

Our list contains few items, for the worst case the only one. It's necessary to make the search because there can be obviously more items. I was surprised by results raised from simple test which is attached at the bottom of current article.

Test simply inserts 1, 50 and finally 100 unique entities to the list. Each entity holds only string identificator (UUID). Each listed algorithm try to find entity placed at the end.

I have tried these approaches:

  1. LINQ query
  2. simple foreach
  3. map having entity id as key

The result is very interesting as attached table and chart show. The map was included only for the confrontation, it obviously doesn't support any querying.

Conclusions: LINQ, foreach or dictionary?



It seems that querying above IList with using LINQ spent significant time to initialize the whole technology. LINQ query can be almost 10x worst than simple foreach for small amount of data. Note that for the described issue, the map is total winner because it has constant search response.



Reject LINQ? No!

The results are not so bad for LINQ as it can be seen. Consider that boundary 7 second is for one million of calls in the case of 50 items within list. So LINQ takes 7 microseconds for one search, foreach six. There is also almost no difference in absolute relations when there is small amount of items within list. LINQ 0.9 microsecond, foreach 0.1 micro. I believe that LINQ can be rejected only for very performance tuned solutions.

Comments

Popular posts from this blog

NHibernate performance issues #3: slow inserts (stateless session)

The whole series of NHibernate performance issues isn't about simple use-cases. If you develop small app, such as simple website, you don't need to care about performance. But if you design and develop huge application and once you have decided to use NHibernate you'll solve various sort of issue. For today the use-case is obvious: how to insert many entities into the database as fast as possible?

Why I'm taking about previous stuff? The are a lot of articles how the original NHibernate's purpose isn't to support batch operations, like inserts. Once you have decided to NHibernate, you have to solve this issue.

Slow insertion
The basic way how to insert mapped entity into database is:
SessionFactory.GetCurrentSession().Save(object);But what happen when I try to insert many entities? Lets say, I want to persist
1000 librarieseach library has 100 books = 100k of bookseach book has 5 rentals - there are 500k of rentals It's really slow! The insertion took exactly

Git on Windows: MSysGit

I have started to use Git today. I read a lot of discussions that there is no good tool for Windows platform. After forethought I have decided to used TortoiseGit. I also feared of difficult work related with Git as a lot of articles mentioned many instructions. As I already said, I have decided to use TortoiseGit, because I'm used to work with TortoiseSvn, but for start, MSysGit is enought. So this article is about MSysGit, next will be about TortoiseGit.

How to start with MSysgit on local machine?
Download and install Git for WindowsCreate source code directory for your git appRight click the directory at your favorite file browser. Menu should contain item "Git init here". It initializes chosen directory to be git-abled :-)It was your first usage of Git.

Commit data to local Git repository

Now, you can add any file, your first source code, to created directory. If you are prepared to commit any changes to your local git repository, follow next instructions.
Right-click th…

Tomcat 7 remote deployment

I decided to provide automatic deployment of war packaged application using Jenkins and Deployment plugin. The target platform is Amazon with Tomcat 7, see nice set of articles to find out how to setup such environment for free.

Well, there is couple of tutorials but they missing some points so it pushed me to lost one hour of my work.

What I gotFresh installation of Tomcat 7 on remote machine with opened 8080 port on firewallPersonal war file supposed to be deployed
How to push it to tomcat?
1. First of all, there is simple configuration of tomcat users in file tomcat-users.xml - it was my pain in the ass :-) As original comprehensive documentation says, it's necessary to define user, but which one(s)?

Here is working example of tomcat-users.xml:

<tomcat-users>
<user username="manager-gui" password="changeit" roles="manager-gui"/>
<user username="manager-script" password="changeit" roles="manager-script"/>