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Editorial Team
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Asked: 2026-05-27T20:50:53+00:00

So I write a Linq query and it takes 16 seconds to run. Decide

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So I write a Linq query and it takes 16 seconds to run. Decide to see what the query plan is, so I get that out of Linq to SQL Profiler and the query only takes 2 seconds to run. sigh

After spending most of the day poking at things and finally getting around to using SQL Server Profiler I see that Linq2SQL is using sp_executesql to run the query. I understand that it’s supposed to improve performance because it’s more likely to re-use the execution plan… but it seems to have chosen a horrible execution plan to use.

The weirder part is that it only gets slow if I join a specific table, and I have no idea why that specific table is causing a problem.

EDIT Just to clarify the actual issue here:

It’s actually getting to different queries. One is, essentially, 

SELECT col1, col2, ... FROM table1, table2 WHERE table1.val IN (1234, 2343, 2435)

The other is 

EXEC sp_executesql 'SELECT col1, col2, ... FROM table1, table2 WHERE table1.val IN (@p1, @p2, @p3)', 
N'@p0 int,@p1 int,@p2 int,@p3 int',
@p0=1234, @p1=2343, @p3=2435
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1 Answer

  1. Editorial Team

    Your problem doesn’t stem from the use of sp_executesql, and so circumventing it (which you can’t) will not solve your problems. I suggest you read Erland Sommarskog’s excellent article:

    Slow in the Application, Fast in SSMS?
    Understanding Performance Mysteries

    This will give you a deep understanding of why you’re getting a performance difference, how to diagnose and consistently reproduce it, and finally, how to solve it.

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