Function RegisterExprContextCallback

src/backend/executor/execUtils.c:982–1000

* Register a shutdown callback in an ExprContext. * * Shutdown callbacks will be called (in reverse order of registration) * when the ExprContext is deleted or rescanned. This provides a hook * for functions called in the context to do any cleanup needed --- it's * particularly useful for functions returning sets. Note that the * callback will *not* be called in the event that execution is

 * by an error.
 */
void
RegisterExprContextCallback(ExprContext *econtext,
							ExprContextCallbackFunction function,
							Datum arg)
{
	ExprContext_CB *ecxt_callback;

	/* Save the info in appropriate memory context */
	ecxt_callback = (ExprContext_CB *)
		MemoryContextAlloc(econtext->ecxt_per_query_memory,
						   sizeof(ExprContext_CB));

	ecxt_callback->function = function;
	ecxt_callback->arg = arg;

	/* link to front of list for appropriate execution order */
	ecxt_callback->next = econtext->ecxt_callbacks;
	econtext->ecxt_callbacks = ecxt_callback;
}

/*
 * Deregister a shutdown callback in an ExprContext.