mvcc/backend/batch_tx.go
func (t *batchTx) Commit() {
	t.Lock()
	t.commit(false)
	t.Unlock()
}
func (t *batchTx) Commit() {
	t.Lock()
	t.commit(false)
	t.Unlock()
}
// Commit commits a previous tx and begins a new writable one.