presto-main/src/main/java/io/prestosql/operator/index/IndexLoader.java/IndexSnapshotLoader/clearCachedData
class IndexSnapshotLoader:        private void clearCachedData()
        {
            indexSnapshotReference.set(new IndexSnapshot(new EmptyLookupSource(outputTypes.size()), new EmptyLookupSource(indexTypes.size())));
            indexSnapshotBuilder.reset();
        }