etcdserver: check invalid range in txn

storage/kv.go

@@ -24,6 +24,11 @@ type KV interface {
 	// Rev returns the current revision of the KV.
 	Rev() int64
 
+	// FirstRev returns the first revision of the KV.
+	// After a compaction, the first revision increases to the compaction
+	// revision.
+	FirstRev() int64
+
 	// Range gets the keys in the range at rangeRev.
 	// If rangeRev <=0, range gets the keys at currentRev.
 	// If `end` is nil, the request returns the key.

storage/kvstore.go

@@ -106,6 +106,13 @@ func (s *store) Rev() int64 {
 	return s.currentRev.main
 }
 
+func (s *store) FirstRev() int64 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	return s.compactMainRev
+}
+
 func (s *store) Put(key, value []byte, lease lease.LeaseID) int64 {
 	id := s.TxnBegin()
 	s.put(key, value, lease)