Directory directory = new MMapDirectory(path);
        try (
            IndexWriter w = new IndexWriter(
                directory,
                new IndexWriterConfig().setOpenMode(OpenMode.CREATE).setRAMBufferSizeMB(indexingBufferMb)
            )
        ) {
            for (int i = 1; i <= 1_000_000; i++) {
                w.addDocument(List.of(new SortedNumericDocValuesField("n", i)));
            }