fix for snapshot iter

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

Author: ekexium

internal/unionstore/art/art_iterator.go

@@ -80,9 +80,11 @@ type Iterator struct {
 
 	// only when seqNo == art.seqNo, the iterator is valid.
 	seqNo int
+	// ignoreSeqNo is used to ignore the seqNo check, used for snapshot iter before its full deprecation.
+	ignoreSeqNo bool
 }
 
-func (it *Iterator) Valid() bool        { return it.valid && it.seqNo == it.tree.SeqNo }
+func (it *Iterator) Valid() bool        { return it.valid && (it.seqNo == it.tree.SeqNo || it.ignoreSeqNo) }
 func (it *Iterator) Key() []byte        { return it.currLeaf.GetKey() }
 func (it *Iterator) Flags() kv.KeyFlags { return it.currLeaf.GetKeyFlags() }
 func (it *Iterator) Value() []byte {
@@ -106,7 +108,7 @@ func (it *Iterator) Next() error {
 		// iterate is finished
 		return errors.New("Art: iterator is finished")
 	}
-	if it.seqNo != it.tree.SeqNo {
+	if !it.ignoreSeqNo && it.seqNo != it.tree.SeqNo {
 		return errors.New(fmt.Sprintf("seqNo mismatch: iter=%d, art=%d", it.seqNo, it.tree.SeqNo))
 	}
 	if it.currAddr == it.endAddr {

internal/unionstore/art/art_snapshot.go

@@ -49,6 +49,7 @@ func (t *ART) newSnapshotIterator(start, end []byte, desc bool) *SnapIter {
 	if err != nil {
 		panic(err)
 	}
+	inner.ignoreSeqNo = true
 	it := &SnapIter{
 		Iterator: inner,
 		cp:       t.getSnapshot(),

internal/unionstore/memdb_test.go

@@ -1336,7 +1336,7 @@ func TestSnapshotReaderWithWrite(t *testing.T) {
 		h := db.Staging()
 		defer db.Release(h)
 
-		iter := db.BatchedSnapshotIter([]byte{0, 0}, []byte{0, 255}, false)
+		iter := db.SnapshotIter([]byte{0, 0}, []byte{0, 255})
 		assert.Equal(t, iter.Key(), []byte{0, 0})
 
 		db.Set([]byte{0, byte(num)}, []byte{0, byte(num)}) // ART: node4/node16/node48 is freed and wait to be reused.