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PO"Order By" in LINQ-to-SQL Causes performance issues
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2261500
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3
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4
CommunityOwnedDate
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2010-02-14T15:06:03.670
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2010-04-28T22:25:21.257
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2010-04-28T22:25:21.257
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825
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Body
I've set out to write a method in my C# application which can return an ordered subset of names from a table containing about 2000 names starting at the 100th name and returning the next 20 names. I'm doing this so I can populate a WPF <code>DataGrid</code> in my UI and do some custom paging. I've been using LINQ to SQL but hit a snag with this long executing query so I'm examining the SQL the LINQ query is using (Query B below). Query A runs well: <pre><code>SELECT TOP (20) [t0].[subject_id] AS [Subject_id], [t0].[session_id] AS [Session_id], [t0].[name] AS [Name] FROM [Subjects] AS [t0] WHERE (NOT (EXISTS( SELECT NULL AS [EMPTY] FROM ( SELECT TOP (100) [t1].[subject_id] FROM [Subjects] AS [t1] WHERE [t1].[session_id] = 1 ORDER BY [t1].[name] ) AS [t2] WHERE [t0].[subject_id] = [t2].[subject_id] ))) AND ([t0].[session_id] = 1) </code></pre> Query B takes 40 seconds: <pre><code>SELECT TOP (20) [t0].[subject_id] AS [Subject_id], [t0].[session_id] AS [Session_id], [t0].[name] AS [Name] FROM [Subjects] AS [t0] WHERE (NOT (EXISTS( SELECT NULL AS [EMPTY] FROM ( SELECT TOP (100) [t1].[subject_id] FROM [Subjects] AS [t1] WHERE [t1].[session_id] = 1 ORDER BY [t1].[name] ) AS [t2] WHERE [t0].[subject_id] = [t2].[subject_id] ))) AND ([t0].[session_id] = 1) ORDER BY [t0].[name] </code></pre> When I add the ORDER BY [t0].[name] to the outer query it slows down the query. How can I improve the second query? <hr> This was my LINQ stuff Nick <pre><code>int sessionId = 1; int start = 100; int count = 20; // Query subjects with the shoot's session id var subjects = cldb.Subjects.Where<Subject>(s => s.Session_id == sessionId); // Filter as per params var orderedSubjects = subjects .OrderBy<Subject, string>( s => s.Col_zero ); var filteredSubjects = orderedSubjects .Skip<Subject>(start) .Take<Subject>(count); </code></pre>
Tags
<.net><linq-to-sql><tsql><sql-server-ce>
Title
"Order By" in LINQ-to-SQL Causes performance issues
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1. PO
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1. USGrokodile
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 PO"Order By" in LINQ-to-SQL Causes performance issues
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 PO"Order By" in LINQ-to-SQL Causes performance issues
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 PO"Order By" in LINQ-to-SQL Causes performance issues
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