address comment

Signed-off-by: you06 <[email protected]>

internal/unionstore/art/art_snapshot.go

@@ -36,9 +36,16 @@ func (t *ART) SnapshotGetter() *SnapGetter {
 	}
 }
 
-// SnapshotIter returns an Iterator for a snapshot of MemBuffer.
-func (t *ART) SnapshotIter(start, end []byte) *SnapIter {
-	inner, err := t.Iter(start, end)
+func (t *ART) newSnapshotIterator(start, end []byte, desc bool) *SnapIter {
+	var (
+		inner *Iterator
+		err   error
+	)
+	if desc {
+		inner, err = t.IterReverse(start, end)
+	} else {
+		inner, err = t.Iter(start, end)
+	}
 	if err != nil {
 		panic(err)
 	}
@@ -53,21 +60,14 @@ func (t *ART) SnapshotIter(start, end []byte) *SnapIter {
 	return it
 }
 
+// SnapshotIter returns an Iterator for a snapshot of MemBuffer.
+func (t *ART) SnapshotIter(start, end []byte) *SnapIter {
+	return t.newSnapshotIterator(start, end, false)
+}
+
 // SnapshotIterReverse returns a reverse Iterator for a snapshot of MemBuffer.
 func (t *ART) SnapshotIterReverse(k, lowerBound []byte) *SnapIter {
-	inner, err := t.IterReverse(k, lowerBound)
-	if err != nil {
-		panic(err)
-	}
-	it := &SnapIter{
-		Iterator: inner,
-		cp:       t.getSnapshot(),
-	}
-	it.tree.allocator.snapshotInc()
-	for !it.setValue() && it.Valid() {
-		_ = it.Next()
-	}
-	return it
+	return t.newSnapshotIterator(k, lowerBound, true)
 }
 
 type SnapGetter struct {
@@ -114,6 +114,8 @@ func (i *SnapIter) Next() error {
 	return nil
 }
 
+// Close releases the resources of the iterator and related version.
+// Make sure to call `Close` after the iterator is not used.
 func (i *SnapIter) Close() {
 	i.Iterator.Close()
 	i.tree.allocator.snapshotDec()