Handling cancel requests

Users of your UDx might cancel the operation while it is running. How Vertica handles the cancellation of the query and your UDx depends on whether your UDx is running in fenced or unfenced mode:

• If your UDx is running in unfenced mode, Vertica either stops the function when it requests a new block of input or output, or waits until your function completes running and discards the results.

• If your UDx is running in Fenced and unfenced modes, Vertica kills the zygote process that is running your function if it continues processing past a timeout.

In addition, you can implement the cancel() method in any UDx to perform any necessary additional work. Vertica calls your function when a query is canceled. This cancellation can occur at any time during your UDx's lifetime, from setup() through destroy().

You can check for cancellation before starting an expensive operation by calling isCanceled().