SQL Server Developer Center: Processing XML Showplans Using SQLCLR in SQL Server 2005

SQL Server Developer Center: Processing XML Showplans Using SQLCLR in SQL Server 2005: "Introduction
Microsoft SQL Server 2005 makes its query execution plans (also known as showplans) available in XML format. XML showplans can be processed using any XML technology�for example, XPath, XQuery, or XSLT. This paper describes an application that extracts the estimated execution cost of a query from its XML showplan. The extracted cost is available for use in a Transact-SQL window. Using this technique, a user can submit to a server running SQL Server only those queries that cost less than a predetermined threshold. This ensures that the server does not get overloaded with costly, long-running queries."