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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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郭元方 updated FLINK-26307:
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Labels: 窗口 (was: )
> 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: 窗口
>
> 对于底层实现窗口时，求其起始时间的方法：
> 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，正确。
> => timestamp - (timestamp - offset + windowSize) % windowSize
> => 1 - (1 -0 + 10) % 10 => start = 0s
> => 7 - (7 -0 + 10) % 10 => start = 0s
> => 12 - (12 - 0 + 10) % 10 => start = 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，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 => start = -10s
> => -7 - (-7 -0 + 10) % 10 => start = -10s
> => -12 - (-12 - 0 + 10) % 10 => start = -10s
> => -15 - (-15 - 0 + 10) % 10 => start = -10s
> => -17 - (-17 - 0 + 10) % 10 => start = -10s
> => -19 - (-19 - 0 + 10) % 10 => start = -10s
>
> 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，现实世界来说不一定，但逻辑上来说应该可以求到负值吧。
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