Linq-to-SQL, group-by, subqueries and performance
If you’re using Linq-to-SQL, doing group-by and selecting other columns than those in the grouping-key, performance might suffer. This is because there is no good translation of such queries to SQL and Linq-to-SQL has to resort to doing multiple subqueries. Matt Warren explains here. I experienced this firsthand when grouping a lot of geocoded events [...]