A.9. Reusable Executions

A translator may return instances of ReusableExecutions for the expected Execution objects. There can be one ReusableExecution per query executing node in the processing plan. The lifecycle of a ReusableExecution is different that a normal Execution . After a normal creation/execute/close cycle the ReusableExecution.reset is called for the next execution cycle. This may occur indefinitely depending on how many times a processing node executes its query. The behavior of the close method is no different from a regular Execution , it may not be called until the end of the statement if lobs are detected and any connection associated with the Execution will also be closed. When the user command is finished, the ReusableExecution.dispose() method will be called.

In general ReusableExecutions are most useful for continuous query execution and will also make use of the ExecutionCotext.dataAvailable() method for Asynchronous Executions. See Red Hat JBoss Development Guide: Client Development for more information about executing continuous statements. In continuous mode the user query will be continuously re-executed. A ReusableExecution allows the same Execution object to be associated with the processing plan for a given processing node for the lifetime of the user query. This can simplify asynch resource management, such as establishing queue listeners. Returning a null result from the next() method ReusableExecution as with normal Executions indicates that the current pushdown command results have ended. Once the reset() method has been called, the next set of results should be returned again terminated with a null result.

See the kit examples for a reusable execution example.