Overriding the Cancel Method

Your User-Defined Transform Function (UDTF) can override the TransformFunction.cancel method that Vertica calls if the query that called the function has been canceled. You should override this method to perform an orderly shutdown of any additional processing that your UDx spawned. For example, you can have your cancel method shut down threads that your UDTF has spawned or signal a third-party library that it needs to stop processing and exit. Your cancel method must leave your UDTF's function class ready to be destroyed, since Vertica calls the UDx's destroy method after the cancel method has exited.

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