How fast is LINQ?

Question

I need to manipulate 100,000 - 200,000 records.
I am thinking of using LINQ (to SQL) to do this.
I know from experience that filtering dataviews is very slow.
So

Answer 1

It depends on what you're trying to do. LINQ has been very fast for me to pull data from the database, but LINQ-to-SQL does directly translate your request to SQL to run it. However, there are times that I've found using Stored Procedures is better in some circumstances.

For instance, I have some data that I need to query which involves several tables, and fairly intense keys. With LINQ, and the relatively inflexibility of LINQ to customize queries, these queries would take several minutes. By hand-tweaking the SQL (namely, by placing 'WHERE'-type arguments in JOIN's in order to minimize the data intensity of the JOIN), I was able to drastically improve performance.

My advice, use LINQ wherever you can, but don't be afraid to go the Stored Procedure route if you determine that the SQL generated by LINQ is simply too slow, and the SQL can be hand-tweaked easily to accomplish what you need.