fix(core): fix read scalar list with rollups (#9350)

Fixes #9338

Author: Harshil Goel

posting/oracle.go

@@ -160,6 +160,8 @@ func (txn *Txn) GetScalarList(key []byte) (*List, error) {
 	if err != nil {
 		return nil, err
 	}
+	l.Lock()
+	defer l.Unlock()
 	if l.mutationMap.len() == 0 && len(l.plist.Postings) == 0 {
 		pl, err := txn.cache.readPostingListAt(key)
 		if err == badger.ErrKeyNotFound {
@@ -168,10 +170,15 @@ func (txn *Txn) GetScalarList(key []byte) (*List, error) {
 		if err != nil {
 			return nil, err
 		}
-		if pl.CommitTs == 0 {
-			l.mutationMap.setCurrentEntries(txn.StartTs, pl)
+
+		if pl.Pack != nil {
+			l.plist = pl
 		} else {
-			l.mutationMap.insertCommittedPostings(pl)
+			if pl.CommitTs == 0 {
+				l.mutationMap.setCurrentEntries(txn.StartTs, pl)
+			} else {
+				l.mutationMap.insertCommittedPostings(pl)
+			}
 		}
 	}
 	return l, nil

worker/sort_test.go

@@ -90,6 +90,61 @@ func TestEmptyTypeSchema(t *testing.T) {
 	x.ParseNamespaceAttr(types[0].TypeName)
 }
 
+func TestGetScalarList(t *testing.T) {
+	dir, err := os.MkdirTemp("", "storetest_")
+	x.Check(err)
+	defer os.RemoveAll(dir)
+
+	opt := badger.DefaultOptions(dir)
+	ps, err := badger.OpenManaged(opt)
+	x.Check(err)
+	pstore = ps
+	posting.Init(ps, 0, false)
+	Init(ps)
+	err = schema.ParseBytes([]byte("scalarPredicateCount4: uid ."), 1)
+	require.NoError(t, err)
+
+	runM := func(startTs, commitTs uint64, edges []*pb.DirectedEdge) {
+		txn := posting.Oracle().RegisterStartTs(startTs)
+		for _, edge := range edges {
+			x.Check(runMutation(context.Background(), edge, txn))
+		}
+		txn.Update()
+		writer := posting.NewTxnWriter(pstore)
+		require.NoError(t, txn.CommitToDisk(writer, commitTs))
+		require.NoError(t, writer.Flush())
+		txn.UpdateCachedKeys(commitTs)
+	}
+
+	attr := x.GalaxyAttr("scalarPredicateCount4")
+
+	runM(5, 7, []*pb.DirectedEdge{{
+		ValueId:   3,
+		ValueType: pb.Posting_UID,
+		Attr:      attr,
+		Entity:    1,
+		Op:        pb.DirectedEdge_SET,
+	}})
+
+	key := x.DataKey(attr, 1)
+	rollup(t, key, ps, 8)
+
+	runM(9, 11, []*pb.DirectedEdge{{
+		ValueId:   5,
+		ValueType: pb.Posting_UID,
+		Attr:      attr,
+		Entity:    1,
+		Op:        pb.DirectedEdge_SET,
+	}})
+
+	txn := posting.Oracle().RegisterStartTs(13)
+	l, err := txn.Get(key)
+	require.Nil(t, err)
+	uids, err := l.Uids(posting.ListOptions{ReadTs: 13})
+	require.Nil(t, err)
+	require.Equal(t, 1, len(uids.Uids))
+}
+
 func TestMultipleTxnListCount(t *testing.T) {
 	dir, err := os.MkdirTemp("", "storetest_")
 	x.Check(err)