Dr. Dobb's Journal - December 2008 - (Page 32)

d12espo_p5db 10/10/08 9:54 AM Page 32 Likewise, a more sophisticated T-SQL code is run when some program goes through the following LINQ code: var data = from customer in context.Customers where customer.Orders.Count > 10 select customer; There’s always a lot of T-SQL code behind any LINQ query that targets a LINQto-SQL collection. Here’s the T-SQL code for the preceding query: SELECT [t0].[CustomerID], [t0].[CompanyName], [t0].[ContactName], [t0].[ContactTitle], [t0].[Address], [t0].[City], [t0].[Region], [t0].[PostalCode], [t0].[Country], [t0].[Phone], [t0].[Fax] FROM [dbo].[Customers] AS [t0] WHERE (( SELECT COUNT(*) FROM [dbo].[Orders] AS [t1] WHERE [t1].[CustomerID] = [t0].[CustomerID] )) > @p0 weight, out-of-the-box, fully integrated in Visual Studio 2008, and limited to SQL Server. Through the DataContext class, the LINQ-to-SQL object model also supports a number of interesting features typical of a full-fledged O/RM tool—including lazy loading, identity and transaction management, and optimistic concurrency. And, of course, the LINQ-to-SQL object model fully supports updates. Updates are not conducted through a direct database operation, but also pass through the DataContext class. You enter changes to the object model and when you’re done, you tell the data context to make changes persistent to the data storage, as in Listing Two. LINQ-to-SQL and SQL Server Development LINQ-to-SQL has the power to autonomously generate good T-SQL statements. Does this mean that LINQ-to-SQL can ultimately replace SQL Server experts in any organization? What about the quality of the T-SQL code being generated? Is there any room left for manual improvement and finetuning? LINQ-to-SQL and O/RM tools in general are not designed to be in contraposition to SQL Server experts. They are just tools in the hands of database experts. However, an O/RM is a high-level tool that other professionals can use as effectively, even when they lack specific SQL Server advanced skills. LINQ-to-SQL is designed to produce TSQL code that is the best possible in the widest possible number of situations. And to get that code written down you don’t have to exercise specific SQL Server skills. This doesn’t mean that LINQ-to-SQL will always employ the perfect T-SQL code for any situation. But it will in a surprisingly large number of situations. The role of a SQL Server expert is just detecting whether there’s room for improvement and introducing it. The LINQ-to-SQL engine buried in the folds of the DataContext object, translates the LINQ query into a T-SQL statement. However, the statement is not immediately run. It executes only when the result set is accessed for reading, enumerated, or simply copied into a memory collection. The effective T-SQL code can be tracked either using the SQL Profiler tool or the Visual Studio 2008 debugger; see Figure 1. Writing queries using the LINQ syntax is much easier and faster for every developer. Moreover, the approach behind LINQ-toSQL takes engineers towards an object-oriented vision of the data that makes it inherently simpler to manage complex scenarios. The primary reason that stopped engineers from widely adopting object-oriented methodologies to design the data model of their applications has been the lack of effective (and especially quick and reliable) mechanisms to make the object model persistent down to a relational database. Objectoriented database-management systems, for a variety of reasons, have yet to capture the hearts of architects and project managers. As a result, an object/relational mismatch has been before our eyes for years. LINQ-to-SQL attempts to provide a simplified solution that, compared to a full O/RM tool, is light32 Dr. Dobb’s Journal l www.ddj.com l December 2008 Fine-Tuning LINQ-to-SQL Code Any class in the LINQ-to-SQL object model is partial, meaning that its source code is not contained in a single class but it may span over two or more distinct source files. By http://www.birdstep.com/database http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - December 2008

Dr. Dobb's Journal - December 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Conversations The Man Who Sold the Sky Performance on Rails LINQ-to-SQL and T-SQL A Remote Java RMI Registry Beyond B-Trees File Descriptors and Multithreaded Programs Effective Concurrency The Agile Edge Swaine's Flames

Dr. Dobb's Journal - December 2008

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