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https://issues.apache.org/jira/browse/FLINK-26307?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Leonard Xu closed FLINK-26307.
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Resolution: Invalid
Please use English in JIRA, feel free to reopen after changing the description
> 当事件时间在（Long.MIN_VALUE ，-windowsize）时，不能正确的求到开启窗口的起始时间
> -----------------------------------------------------
>
> Key: FLINK-26307
> URL: https://issues.apache.org/jira/browse/FLINK-26307
> Project: Flink
> Issue Type: Improvement
> Components: API / DataStream
> Affects Versions: 1.13.6
> Reporter: 郭元方
> Priority: Major
> Labels: 事件时间, 水位线, 窗口
>
> 对于底层实现窗口时，求其开启窗口起始时间的方法有一个问题：
> public static long getWindowStartWithOffset(long timestamp, long offset, long
> windowSize)
> { return timestamp - (timestamp - offset + windowSize) % windowSize;
> }
> 例如：窗口大小为10，事件时间分别为1s，7s，12s得到的起始时间，显然正确。
> => timestamp - (timestamp - offset + windowSize) % windowSize
> => 1 - (1 -0 + 10) % 10 => WindowStart = 0s
> => 7 - (7 -0 + 10) % 10 => WindowStart = 0s
> => 12 - (12 - 0 + 10) % 10 => WindowStart = 10s
>
> 但是，当事件时间为
> -1s，-7s，-12s，-15s，-17s，-19s时，窗口的起始时间却也都为-10s，事件时间为-21s，-27s，窗口起始时间为-20s
> 是否由于在java中的取余规则，正数对正数取余的商值向0逼近，而负数对正数取余的商值也向0逼近导致该算法
> 对事件时间在（Long.MIN_VALUE，-windowsize）的这个范围内的数据不能正确的求到开启窗口的起始时间呢？
> => timestamp - (timestamp - offset + windowSize) % windowSize
> => -1 - (-1 -0 + 10) % 10 => WindowStart = -10s
> => -7 - (-7 -0 + 10) % 10 => WindowStart = -10s
> => -12 - (-12 - 0 + 10) % 10 => WindowStart = -10s
> => -15 - (-15 - 0 + 10) % 10 => WindowStart = -10s
> => -17 - (-17 - 0 + 10) % 10 => WindowStart = -10s
> => -19 - (-19 - 0 + 10) % 10 => WindowStart = -10s
> => -23 - (-23 - 0 + 10) % 10 =>WindowStart = -20s
> => -27 - (-27 - 0 + 10) % 10 => WindowStart = -20s
> {code:java}
> //代码占位符
> env
> .fromElements(
> new LoginEvent("user-1", "fail", -7L),
> new LoginEvent("user-2", "success", -23L)
> )
>
> .assignTimestampsAndWatermarks(WatermarkStrategy.<LoginEvent>forMonotonousTimestamps()
> .withTimestampAssigner(new
> SerializableTimestampAssigner<LoginEvent>() {
> @Override
> public long extractTimestamp(LoginEvent element, long
> recordTimestamp) {
> return element.ts;
> }
> }))
> .keyBy(r -> r.userId)
>
> .window(SlidingEventTimeWindows.of(Time.milliseconds(10),Time.milliseconds(5)))
> .process(
> new ProcessWindowFunction<LoginEvent, String, String,
> TimeWindow>() {
> @Override
> public void process(String s, Context context,
> Iterable<LoginEvent> elements, Collector<String> out) throws Exception {
> out.collect(
> "窗口" + context.window().getStart() + "~" +
> context.window().getEnd() + "中的元素为：" +
> elements.iterator().next().ts
> );
> }
> }
> )
> .print();
> env.execute();
> 执行结果如下：
> 窗口-30~-20中的元素为：-23
> 窗口-25~-15中的元素为：-23
> 窗口-20~-10中的元素为：-23
> 窗口-15~-5中的元素为：-7
> 窗口-10~0中的元素为：-7
> 窗口-5~5中的元素为：-7
> 结论：
> 显然-7 不在 -5~5的窗口，-23不在-10~-20的窗口。{code}
>
> 和同学邓子琦的讨论，并没有经历过业务，所以此处事件时间求到了负值，仅从逻辑上来讲，事件时间应该可以为负值吧。
> 求大佬解答，该算法算不算有逻辑上的漏洞。
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