使用具有较大结果集的实体框架5的性能问题

Question

I'm using Entity Framework 5, and I'm executing a query that returns a relatively large resultset, around 30,000 rows. The query itself executes very fast, taking only around 700ms.

After building the linq query I call query.Load(); , and then return DataContext.Set<MyType>.Local as an ObservableCollection to the caller. The results are displayed in an editable grid.

The problem is with the query.Load(); call - it's taking around 60 seconds, which is way too long. I'm guessing that this is where EF transforms the results into .NET objects? I've tried profiling, but it won't go any deeper than IQueryable.Load :/

Any ideas how can I improve performance?

BTW, I tried upgrading to EF6 to see if that helped any, but it actually got worse, wih query.Load(); typically taking 100 seconds!

Answer 1

The Linq to Entities query is not executed until the results are needed. That's when the computational cost is "paid". Until then, the query is just a query. As Stefan suggested, you should try add some filters, or at least a paging mechanism using .Skip and .Take methods.

You could also check this MSDN article about linq paging.

Hope I helped!