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

How long is a piece of string? How fast is LInq to SQL. It depends on how you use it.

"filtering dataviews is very slow" becuase in this model you retrieve all the records and then filter on the client. But Linq to SQL doesn't work like that unless you abuse it.

A Linq query is only evaluated at the last possible minute that it has to be. So you can add "where" restrictions on a query before it is evaluated. The whole expression, including the filters, will execute on the database, as it should.

Stackoverflow uses Linq, and it's not a small database.

Some will advocate stored procs to access your database over SQL or ORMS. This has been debated in other questions. Eg here and here

My opinion is that for some things, you will want a professional DBA to craft an optimal stored proc. You can then access this from Linq if you want. But 80% or more of the database access methods won't be performance-critical, and stored procs can be time-consuming overkill for these.

For updates, set-based server-side operations in a stored proc or sql with an "update ... where ... " will be a lot faster than using multiple database round-trips to read a record, write a record, repeat.