[jira] [Created] (FLINK-12714) confusion about flink time window TimeWindow#getWindowStartWithOffset

["Wenshuai Hou (JIRA)" <ji...@apache.org>]

Wenshuai Hou created FLINK-12714:
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             Summary: confusion about flink time window TimeWindow#getWindowStartWithOffset
                 Key: FLINK-12714
                 URL: https://issues.apache.org/jira/browse/FLINK-12714
             Project: Flink
          Issue Type: Improvement
          Components: flink-contrib
    Affects Versions: 1.8.0
            Reporter: Wenshuai Hou


 

hi flink team, i think the flink doc on how time windows are created an the javadoc of related method is a little confusing. They give me the impression that the window-start equals to the timestamp of the first event assigned to that window, however the window-start is actually quantized by the windowSize, see links below. Is this the intention or is this a mistake? can we please leave a comment in flink doc somewhere to make this more clear? I spent 5 hours wondering why my flink tests fail until i find that method. 

 

Thanks 

Wen 

 

links: 

================

 

The flink doc from here : [https://ci.apache.org/projects/flink/flink-docs-stable/dev/stream/operators/windows.html#window-lifecycle] 

> In a nutshell, a window is *created* as soon as the first element that should belong to this window arrives

 

the java doc of this method:  org.apache.flink.streaming.api.windowing.windows.TimeWindow#getWindowStartWithOffset

 

 
{code:java}
/**
 * Method to get the window start for a timestamp.
 *
 * @param timestamp epoch millisecond to get the window start.
 * @param offset The offset which window start would be shifted by.
 * @param windowSize The size of the generated windows.
 * @return window start
 */
public static long getWindowStartWithOffset(long timestamp, long offset, long windowSize) {

{code}
 

 

 

 



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