Entity Framework query performance differs extrem with raw SQL execution

Question

I have a question about Entity Framework query execution performance.

Schema:

I have a table structure like this:

CREATE TABLE [         


        

Answer 1

The DB engine determines the plan for each query based on how it is called. In case of your EF Linq query, the plan is prepared in such a way that each input parameter is treated as an unknown(since you have no idea what's coming in). In your actual query, you have all you parameters as part of the query so it will run under a different plan than that for a parameterized one. One of the affected piece that I see immediately is

...(@p__linq__0 IS NULL)..

This is FALSE since p_linq_0 = 20827 and is NOT NULL, so your first half of the WHERE is FALSE to begin with and does not need to be looked at any more. In case of LINQ queries, the DB has no idea what's coming in so evaluates everything anyway.

You'll need to see if you can use indices or other techniques to make this run faster.