What to do if user closes page in the middle of a mysql long query?

W开发者_如何学Gohat happens to the mysql query if the user just closes the page? Should I be doing any kind of checking for this? I'm using JPA 2.0(EclipseLink 2.0), JSF 2.0, EJB 3.1(lite) and Glassfish 3.1. Thanks.

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In the database, the query will continue to run until completion. It's possible to kill the session running the query, but there's a security concern with providing that ability outside of the database.

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Generally there's nothing you can do to detect it or abort a query in progress. You're stuck with using up the CPU time to finish the process because there's no way to interrupt a query in progress from Java.

Why would this be an issue? What is it that you're trying to avoid?

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In JPA you can define a timeout which is passed to JDBC. You can also set a maxResults to limit the number of rows returned.

JDBC now also provides a cancel() API, but JPA does not yet expose this.