@VisibleForTesting
    void closeCurrentPage() {
        sorter.closeCurrentPage();
    }
Marks the current page as no-more-space-available, and as a result, either allocate a
new page or spill when we see the next record.
indexr-query-opt/src/main/java/org/apache/spark/sql/execution/UnsafeKVExternalSorter.java