LINQ's Skip()/Take() vs. Custom SQL: Which Paging Method Offers Better Efficiency?

Efficient paging implementation: Comparison of the efficiency of LINQ's Skip()/Take() and custom SQL

In your pagination implementation, you may need to choose between LINQ's Skip() and Take() methods and a custom SQL paging scheme. This article will analyze the efficiency and advantages of both methods to help you make the best decision.

LINQ’s Skip() and Take() methods

LINQ provides a simple paging implementation. The Skip() method skips the specified number of rows, and the Take() method obtains the subsequent specified number of rows, thereby easily implementing paging. In SQL Server 2008 and later, these methods leverage the ROW_NUMBER() function to perform paging directly inside the SQL engine.

For example, the following LINQ query:

<code class="language-csharp">var query = (from c1 in c.MtCity2s
                select c1).Skip(3).Take(3);</code>

will be converted into the following SQL statement:

<code class="language-sql">SELECT [t1].[CodCity], 
    [t1].[CodCountry], 
    [t1].[CodRegion], 
    [t1].[Name],  
    [t1].[Code]
FROM (
    SELECT ROW_NUMBER() OVER (
        ORDER BY [t0].[CodCity], 
        [t0].[CodCountry], 
        [t0].[CodRegion], 
        [t0].[Name],
        [t0].[Code]) AS [ROW_NUMBER], 
        [t0].[CodCity], 
        [t0].[CodCountry], 
        [t0].[CodRegion], 
        [t0].[Name],
        [t0].[Code]
    FROM [dbo].[MtCity] AS [t0]
    ) AS [t1]
WHERE [t1].[ROW_NUMBER] BETWEEN @p0 + 1 AND @p0 + @p1
ORDER BY [t1].[ROW_NUMBER]</code>

This query demonstrates SQL's windowed data access method, which can start returning data immediately and continue to access the table based on specified conditions.

Customized SQL paging implementation

Another approach is to create a custom SQL-based paging mechanism. To improve performance, you can use stored procedures to encapsulate logic and leverage indexes where appropriate. An example is as follows:

<code class="language-sql">With CityEntities As 
(
    Select ROW_NUMBER() Over (Order By CodCity) As Row,
        CodCity 
    From dbo.mtcity
)
Select [t0].[CodCity], 
        [t0].[CodCountry], 
        [t0].[CodRegion], 
        [t0].[Name],
        [t0].[Code]
From CityEntities c
Inner Join dbo.MtCity t0 on c.CodCity = t0.CodCity
Where c.Row Between @p0 + 1 AND @p0 + @p1
Order By c.Row Asc</code>

This query creates an in-memory table called CityEntities that contains the row number for each row in the mtcity table. By using an index on the CodCity column, the query can efficiently retrieve the required rows.

Choose the most effective method

The choice between these two methods depends largely on the complexity of your logic. If your workflow is relatively simple, the LINQ approach will suffice. However, for more complex logic, it may be more efficient and flexible to implement your own SQL-based paging solution.

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