code: public void unsetExecutorIdForExecution(final int executionId) throws ExecutorManagerException {
      final String UNSET_EXECUTOR = "UPDATE execution_flows SET executor_id = null where exec_id = ?";
  
      final SQLTransaction<Integer> unsetExecutor =
          transOperator -> transOperator.update(UNSET_EXECUTOR, executionId);
  
      try {
        this.dbOperator.transaction(unsetExecutor);
      } catch (final SQLException e) {
        throw new ExecutorManagerException("Error unsetting executor id for execution " + executionId,
            e);
      }
    }
docs: set executor id to null for the execution id