Skip orphan metadata if versioning is not needed

mutable_tree.go

@@ -1070,6 +1070,13 @@ func (tree *MutableTree) SetInitialVersion(version uint64) {
 func (tree *MutableTree) DeleteVersions(versions ...int64) error {
 	logger.Debug("DELETING VERSIONS: %v\n", versions)
 
+	if tree.ndb.ShouldNotUseVersion() {
+		// no need to delete versions since there is no version to be
+		// deleted except the current one, which shouldn't be deleted
+		// in any circumstance
+		return nil
+	}
+
 	if len(versions) == 0 {
 		return nil
 	}

nodedb.go

@@ -634,6 +634,18 @@ func (ndb *nodeDB) SaveOrphans(version int64, orphans map[string]int64) error {
 	ndb.mtx.Lock()
 	defer ndb.mtx.Unlock()
 
+	// instead of saving orphan metadata and later read orphan metadata->delete
+	// orphan data->delete orphan metadata, we directly delete orphan data here
+	// without doing anything for orphan metadata, if versioning is not needed.
+	if ndb.ShouldNotUseVersion() {
+		for orphan := range orphans {
+			if err := ndb.deleteOrphanedData([]byte(orphan)); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
 	toVersion, err := ndb.getPreviousVersion(version)
 	if err != nil {
 		return err
@@ -649,6 +661,14 @@ func (ndb *nodeDB) SaveOrphans(version int64, orphans map[string]int64) error {
 	return nil
 }
 
+func (ndb *nodeDB) deleteOrphanedData(hash []byte) error {
+	if err := ndb.batch.Delete(ndb.nodeKey(hash)); err != nil {
+		return err
+	}
+	ndb.nodeCache.Remove(hash)
+	return nil
+}
+
 // Saves a single orphan to disk.
 func (ndb *nodeDB) saveOrphan(hash []byte, fromVersion, toVersion int64) error {
 	if fromVersion > toVersion {
@@ -1053,6 +1073,10 @@ func (ndb *nodeDB) traverseNodes(fn func(hash []byte, node *Node) error) error {
 	return nil
 }
 
+func (ndb *nodeDB) ShouldNotUseVersion() bool {
+	return ndb.opts.NoVersioning
+}
+
 func (ndb *nodeDB) String() (string, error) {
 	buf := bufPool.Get().(*bytes.Buffer)
 	defer bufPool.Put(buf)

options.go

@@ -81,6 +81,10 @@ type Options struct {
 
 	// When Stat is not nil, statistical logic needs to be executed
 	Stat *Statistics
+
+	// When set to true, the DB will only keep the most recent version and immediately delete
+	// obsolete data upon new data's commit
+	NoVersioning bool
 }
 
 // DefaultOptions returns the default options for IAVL.