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POEntity Framework Performance Issue
 

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  1. POEntity Framework Performance Issue
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    <p>I am running into an interesting performance issue with Entity Framework. I am using Code First.</p> <p>Here is the structure of my entities:</p> <p>A Book can have many Reviews. A Review is associated with a single Book. A Review can have one or many Comments. A Comment is associated with one Review.</p> <pre><code>public class Book { public int BookId { get; set; } // ... public ICollection&lt;Review&gt; Reviews { get; set; } } public class Review { public int ReviewId { get; set; } public int BookId { get; set; } public Book Book { get; set; } public ICollection&lt;Comment&gt; Comments { get; set; } } public class Comment { public int CommentId { get; set; } public int ReviewId { get; set; } public Review Review { get; set; } } </code></pre> <p>I populated my database with a lot of data and added the proper indexes. I am trying to retrieve a single book that has 10,000 reviews on it using this query:</p> <pre><code>var bookAndReviews = db.Books.Where(b =&gt; b.BookId == id) .Include(b =&gt; b.Reviews) .FirstOrDefault(); </code></pre> <p>This particular book has 10,000 reviews. The performance of this query is around 4 seconds. Running the exact same query (via SQL Profiler) actually returns in no time at all. I used the same query and a SqlDataAdapter and custom objects to retrieve the data and it happens in under 500 milliseconds.</p> <p>Using ANTS Performance Profiler it looks like a bulk of the time is being spent doing a few different things:</p> <p><strong>The Equals method is being called 50 million times.</strong></p> <p>Does anyone know why it would need to call this 50 million times and how I could increase the performance for this? </p>
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    1. CODid you actually look to see what query is being generated by your statement or are you assuming it is the optimal query?
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      1. USJustin Niessner
    2. COGive EF Profiler a try.
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      1. USDerek Beattie
    3. COThe problem is not the query like I have stated. I took the exact query that EF is generating and used it in a Sql Data Adapter using regular ADO.net, loading up the same objects manually. It runs in less than a second.
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