1.2 Terrabyte 文件的慢趋势 sax 解析

如何解决1.2 Terrabyte 文件的慢趋势 sax 解析

我喜欢解析行星（osm planet-200309.xml ~1.26tb）

为了计算使用 java 最少需要多长时间，我创建了一个小的 sax-parsing-application:

    final File f = new File("f:/planet-200309.xml");
    SAXParserFactory newInstance = SAXParserFactory.newInstance();
    final long start = System.currentTimeMillis();
    final CountingInputStream cif = new CountingInputStream(new FileInputStream(f));
    Thread t = new Thread() {
        public void run() {
            try {
                while (cif.available() > 0) {
                    Thread.sleep(10000);
                    long stop = System.currentTimeMillis();
                    long seconds = (stop - start) / 1000;
                    long bytesRead = cif.getBytesRead();
                    float bytePerSecond = bytesRead / seconds;
                    int expectedSeconds = (int) (f.length() / bytePerSecond);
                    System.out.println("Expected minutes: " + expectedSeconds / 60 + ",bytes per second:" + (int) bytePerSecond + " (reat: " + bytesRead
                            + ",took: " + seconds + ")");
                }
            } catch (IOException e) {
                e.printstacktrace();
            } catch (InterruptedException e) {
                e.printstacktrace();
            }
        };
    };
    t.start();

    newInstance.newSAXParser().parse(cif,new DefaultHandler() {
        @Override
        public void startElement(String uri,String localName,String qName,Attributes attributes) throws SAXException {
            if (!qName.equals("changeset") & !qName.equals("tag")) {
                System.out.println(qName);
            }
        }
    });

    long stop = System.currentTimeMillis();
    long took = stop - start;
    System.out.println(took / 1000);

我决定每 10 秒计算一次需要多长时间。这是我的输出：

Expected minutes: 174,bytes per second:122728576 (reat: 1227285768,took: 10)
Expected minutes: 173,bytes per second:123918400 (reat: 2478367973,took: 20)
Expected minutes: 172,bytes per second:124213368 (reat: 3726401103,took: 30)
Expected minutes: 175,bytes per second:122289280 (reat: 4891571271,took: 40)
Expected minutes: 186,bytes per second:115111152 (reat: 5755557747,took: 50)
Expected minutes: 197,bytes per second:108455448 (reat: 6507327092,took: 60)
Expected minutes: 212,bytes per second:100975920 (reat: 7068314710,took: 70)
Expected minutes: 224,bytes per second:95568256 (reat: 7645460576,took: 80)
Expected minutes: 236,bytes per second:90757120 (reat: 8168140838,took: 90)
Expected minutes: 237,bytes per second:90276424 (reat: 9027642303,took: 100)
Expected minutes: 240,bytes per second:89072968 (reat: 9798026674,took: 110)
Expected minutes: 250,bytes per second:85678456 (reat: 10281415054,took: 120)
Expected minutes: 257,bytes per second:83305712 (reat: 10829743052,took: 130)
Expected minutes: 256,bytes per second:83664016 (reat: 11712962690,took: 140)
Expected minutes: 250,bytes per second:85531576 (reat: 12829736785,took: 150)

在前 10 秒内，我计算了大约 3 小时的时间消耗。两分钟后，我计算了 4 小时的时间消耗。

有趣的是：似乎有一种趋势是放慢萨克斯解析。

我将这些值放入图表中：

这里有什么问题？为什么趋势放缓？