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mvcc: only write txn should update index

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This commit is contained in:
Xiang Li 2016-08-22 22:04:33 -07:00
parent 028b954052
commit e1789aa531
1 changed files with 15 additions and 3 deletions
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14
mvcc/kvstore.go
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@ -76,6 +76,7 @@ type store struct {
tx backend.BatchTx tx backend.BatchTx
txnID int64 // tracks the current txnID to verify txn operations txnID int64 // tracks the current txnID to verify txn operations
txnModify bool
// bytesBuf8 is a byte slice of length 8 // bytesBuf8 is a byte slice of length 8
// to avoid a repetitive allocation in saveIndex. // to avoid a repetitive allocation in saveIndex.
@ -180,7 +181,6 @@ func (s *store) TxnBegin() int64 {
s.currentRev.sub = 0 s.currentRev.sub = 0
s.tx = s.b.BatchTx() s.tx = s.b.BatchTx()
s.tx.Lock() s.tx.Lock()
s.saveIndex()
s.txnID = rand.Int63() s.txnID = rand.Int63()
return s.txnID return s.txnID
@ -203,6 +203,14 @@ func (s *store) txnEnd(txnID int64) error {
return ErrTxnIDMismatch return ErrTxnIDMismatch
} }
// only update index if the txn modifies the mvcc state.
// read only txn might execute with one write txn concurrently,
// it should not write its index to mvcc.
if s.txnModify {
s.saveIndex()
}
s.txnModify = false
s.tx.Unlock() s.tx.Unlock()
if s.currentRev.sub != 0 { if s.currentRev.sub != 0 {
s.currentRev.main += 1 s.currentRev.main += 1
@ -502,6 +510,8 @@ func (s *store) rangeKeys(key, end []byte, limit, rangeRev int64, countOnly bool
} }
func (s *store) put(key, value []byte, leaseID lease.LeaseID) { func (s *store) put(key, value []byte, leaseID lease.LeaseID) {
s.txnModify = true
rev := s.currentRev.main + 1 rev := s.currentRev.main + 1
c := rev c := rev
oldLease := lease.NoLease oldLease := lease.NoLease
@ -568,6 +578,8 @@ func (s *store) put(key, value []byte, leaseID lease.LeaseID) {
} }
func (s *store) deleteRange(key, end []byte) int64 { func (s *store) deleteRange(key, end []byte) int64 {
s.txnModify = true
rrev := s.currentRev.main rrev := s.currentRev.main
if s.currentRev.sub > 0 { if s.currentRev.sub > 0 {
rrev += 1 rrev += 1