commit ndb batch and remove lazy parameter

mutable_tree.go

@@ -615,17 +615,8 @@ func (tree *MutableTree) LoadVersion(targetVersion int64) (int64, error) {
 
 // LoadVersionForOverwriting attempts to load a tree at a previously committed
 // version, or the latest version below it. Any versions greater than targetVersion will be deleted.
-// When lazy=true, call `LazyLoadVersion` instead of `LoadVersion`.
-func (tree *MutableTree) LoadVersionForOverwriting(targetVersion int64, lazy bool) (int64, error) {
-	var (
-		latestVersion int64
-		err           error
-	)
-	if lazy {
-		latestVersion, err = tree.LazyLoadVersion(targetVersion)
-	} else {
-		latestVersion, err = tree.LoadVersion(targetVersion)
-	}
+func (tree *MutableTree) LoadVersionForOverwriting(targetVersion int64) (int64, error) {
+	latestVersion, err := tree.LoadVersion(targetVersion)
 	if err != nil {
 		return latestVersion, err
 	}
@@ -634,11 +625,15 @@ func (tree *MutableTree) LoadVersionForOverwriting(targetVersion int64, lazy boo
 		return latestVersion, err
 	}
 
-	tree.ndb.resetLatestVersion(latestVersion)
+	if err := tree.ndb.Commit(); err != nil {
+		return latestVersion, err
+	}
 
 	tree.mtx.Lock()
 	defer tree.mtx.Unlock()
 
+	tree.ndb.resetLatestVersion(latestVersion)
+
 	if !tree.skipFastStorageUpgrade {
 		// it'll repopulates the fast node index because of version mismatch.
 		if _, err := tree.enableFastStorageAndCommitIfNotEnabled(); err != nil {