func (ca twoPhaseCommitAction) String() string {
	switch ca {
	case actionPrewrite:
		return "prewrite"
	case actionCommit:
		return "commit"
	case actionCleanup:
		return "cleanup"
	case actionPessimisticLock:
		return "pessimistic_lock"
	case actionPessimisticRollback:
		return "pessimistic_rollback"
	}
	return "unknown"
}

func (c *twoPhaseCommitter) getProcFuncByType(action twoPhaseCommitAction) (procOneBatchFn, error) {
	var singleBatchActionFunc procOneBatchFn
	switch action {
	case actionPrewrite:
		singleBatchActionFunc = c.prewriteSingleBatch
	case actionCommit:
		singleBatchActionFunc = c.commitSingleBatch
	case actionCleanup:
		singleBatchActionFunc = c.cleanupSingleBatch
	case actionPessimisticLock:
		singleBatchActionFunc = c.pessimisticLockSingleBatch
	case actionPessimisticRollback:
		singleBatchActionFunc = c.pessimisticRollbackSingleBatch
	default:
		return nil, errors.Errorf("invalid action type=%v", action)
	}
	return singleBatchActionFunc, nil
}

type procOneBatchFn func(bo *Backoffer, batch batchKeys) error

func(bo *Backoffer, killed *uint32, batch batchKeys)