Why is Entity Framework taking 30 seconds to load records when the generated query only takes 1/2 of a second?

Question

The executeTime below is 30 seconds the first time, and 25 seconds the next time I execute the same set of code. When watching in SQL Profiler, I immediately see a login, t

Answer 1

The only way to make the initial compilation of the query faster that I know of is to make the query less complex. The MSDN documentation on performance considerations for the Entity Framework and Compiled Queries don't indicate that there is any way to save a compiled query for use in a different application execution session.

I would add that we have found that having lots of Includes can make query execution slower than having fewer Includes and doing more Loads on related entities later. Some trial and error is required to find the right medium.

However, I have to ask if you really need every property of every entity you are including here. It seems to me that there is a large number of different entity types in this query, so materializing them could well be quite expensive. If you are just trying to get tabular results which you don't intend to update, projecting the (relatively) fewer number of fields that you actually need into a flat, anonymous type should be significantly faster for various reasons. Also, this frees you from having to worry about eager loading, calling Load/IsLoaded, etc.

You can certainly speed up the initial view generation by precompiling the entity views. There is documentation on MSDN for this. But since you pay that cost at the time the first query is executed, your test with a simple query shows that this is running in the neighborhood of 2 seconds for you. It's nice to say that 2 seconds, but it won't save anything else.