code: func (e *UnionExec) Close() error {
  	close(e.finished)
  	e.childrenResults = nil
  	if e.resultPool != nil {
  		for range e.resultPool {
  		}
  	}
  	e.resourcePools = nil
  	return e.baseExecutor.Close()
  }
docs: // Close implements the Executor Close interface.