private void slowTruncate(Session session, Table table, boolean descendants) {
final com.foundationdb.qp.rowtype.Schema schema = SchemaCache.globalSchema(table.getAIS());
final Set<TableRowType> filterTypes;
if(descendants) {
filterTypes = new HashSet<>();
table.visit(new AbstractVisitor() {
@Override
public void visit(Table t) {
TableRowType rowType = schema.tableRowType(t);
assert rowType != null : t;
filterTypes.add(rowType);