[jira] [Created] (FLINK-7245) Enhance the operators to support holding back watermarks

["Xingcan Cui (JIRA)" <ji...@apache.org>]

Xingcan Cui created FLINK-7245:
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             Summary: Enhance the operators to support holding back watermarks
                 Key: FLINK-7245
                 URL: https://issues.apache.org/jira/browse/FLINK-7245
             Project: Flink
          Issue Type: New Feature
          Components: DataStream API
            Reporter: Xingcan Cui
            Assignee: Xingcan Cui


Currently the watermarks are applied and emitted by the {{AbstractStreamOperator}} instantly. 
{code:java}
public void processWatermark(Watermark mark) throws Exception {
	if (timeServiceManager != null) {
		timeServiceManager.advanceWatermark(mark);
	}
	output.emitWatermark(mark);
}
{code}

Some calculation results (with timestamp fields) triggered by these watermarks (e.g., join or aggregate results) may be regarded as delayed by the downstream operators since their timestamps must be less than or equal to the corresponding triggers. 

This issue aims to add another "working mode", which supports holding back watermarks, to current operators. These watermarks should be blocked and stored by the operators until all the corresponding new generated results are emitted.



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