Follow up etcd-io#16068 (comment)

 Add a UnsafeReadScheduledCompact and UnsafeReadFinishedCompact

Signed-off-by: caojiamingalan <alan.c.19971111@gmail.com>

server/mvcc/kvstore.go

@@ -232,19 +232,9 @@ func (s *store) checkPrevCompactionCompleted() bool {
 	tx := s.b.ReadTx()
 	tx.Lock()
 	defer tx.Unlock()
-	_, scheduledCompactBytes := tx.UnsafeRange(buckets.Meta, scheduledCompactKeyName, nil, 0)
-	scheduledCompact := int64(0)
-	if len(scheduledCompactBytes) != 0 {
-		scheduledCompact = bytesToRev(scheduledCompactBytes[0]).main
-	}
-
-	_, finishedCompactBytes := tx.UnsafeRange(buckets.Meta, finishedCompactKeyName, nil, 0)
-	finishedCompact := int64(0)
-	if len(finishedCompactBytes) != 0 {
-		finishedCompact = bytesToRev(finishedCompactBytes[0]).main
-
-	}
-	return scheduledCompact == finishedCompact
+	scheduledCompact, scheduledCompactFound := UnsafeReadScheduledCompact(tx)
+	finishedCompact, finishedCompactFound := UnsafeReadFinishedCompact(tx)
+	return scheduledCompact == finishedCompact && scheduledCompactFound == finishedCompactFound
 }
 
 func (s *store) compact(trace *traceutil.Trace, rev, prevCompactRev int64, prevCompactionCompleted bool) (<-chan struct{}, error) {
@@ -343,10 +333,10 @@ func (s *store) restore() error {
 	tx := s.b.ReadTx()
 	tx.Lock()
 
-	_, finishedCompactBytes := tx.UnsafeRange(buckets.Meta, finishedCompactKeyName, nil, 0)
-	if len(finishedCompactBytes) != 0 {
+	finishedCompact, found := UnsafeReadFinishedCompact(tx)
+	if found {
 		s.revMu.Lock()
-		s.compactMainRev = bytesToRev(finishedCompactBytes[0]).main
+		s.compactMainRev = finishedCompact
 
 		s.lg.Info(
 			"restored last compact revision",
@@ -356,11 +346,7 @@ func (s *store) restore() error {
 		)
 		s.revMu.Unlock()
 	}
-	_, scheduledCompactBytes := tx.UnsafeRange(buckets.Meta, scheduledCompactKeyName, nil, 0)
-	scheduledCompact := int64(0)
-	if len(scheduledCompactBytes) != 0 {
-		scheduledCompact = bytesToRev(scheduledCompactBytes[0]).main
-	}
+	scheduledCompact, _ := UnsafeReadScheduledCompact(tx)
 
 	// index keys concurrently as they're loaded in from tx
 	keysGauge.Set(0)

server/mvcc/util.go

@@ -41,3 +41,19 @@ func UnsafeSetScheduledCompact(tx backend.BatchTx, value int64) {
 	revToBytes(revision{main: value}, rbytes)
 	tx.UnsafePut(buckets.Meta, scheduledCompactKeyName, rbytes)
 }
+
+func UnsafeReadFinishedCompact(tx backend.ReadTx) (finishedCompact int64, found bool) {
+	_, finishedCompactBytes := tx.UnsafeRange(buckets.Meta, finishedCompactKeyName, nil, 0)
+	if len(finishedCompactBytes) != 0 {
+		return bytesToRev(finishedCompactBytes[0]).main, true
+	}
+	return 0, false
+}
+
+func UnsafeReadScheduledCompact(tx backend.ReadTx) (scheduledCompact int64, found bool) {
+	_, scheduledCompactBytes := tx.UnsafeRange(buckets.Meta, scheduledCompactKeyName, nil, 0)
+	if len(scheduledCompactBytes) != 0 {
+		return bytesToRev(scheduledCompactBytes[0]).main, true
+	}
+	return 0, false
+}