store/tikv: tiny refactoring, change twoPhaseCommitAction to interface

[tiancaiamao]

What problem does this PR solve?

We define type twoPhaseCommitAction int and use switch case on them.

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
}

I need to closure some data on pessimisticLockSingleBatch, but I think it's improper to change the

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

to something like

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

so I think using interface is more flexible.

What is changed and how it works?

change twoPhaseCommitAction to interface.

Check List

Tests

• No code

Related changes

• Need to cherry-pick to the release branch
  This refactoring is prepared for an incoming bug-fix PR

[tiancaiamao]

PTAL @coocood @lysu @cfzjywxk

[lysu]

LGTM

[lysu]

type (
   actionPrewrite struct{}
   actionCommit struct{}
   actionCleanup struct{}
   actionPessimisticLock struct{}
   actionPessimisticRollback struct{}
)

we can avoid duplicate type words~

[jackysp]

LGTM

[cfzjywxk]

LGTM

[coocood]

LGTM

[coocood]

/run-unit-test

[sre-bot]

Your auto merge job has been accepted, waiting for 12608

[codecov]

Codecov Report

Merging #12845 into master will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master     #12845   +/-   ##
===========================================
  Coverage   80.0972%   80.0972%           
===========================================
  Files           465        465           
  Lines        106980     106980           
===========================================
  Hits          85688      85688           
  Misses        14893      14893           
  Partials       6399       6399

[sre-bot]

/run-all-tests

[sre-bot]

cherry pick to release-3.1 failed

[sre-bot]

cherry pick to release-3.0 failed

[crazycs520]

@tiancaiamao Need cherry pick to 3.1?