[jira] [Created] (FLINK-19317) Make EventTime the default StreamTimeCharacteristic

["Aljoscha Krettek (Jira)" <ji...@apache.org>]

Aljoscha Krettek created FLINK-19317:
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             Summary: Make EventTime the default StreamTimeCharacteristic
                 Key: FLINK-19317
                 URL: https://issues.apache.org/jira/browse/FLINK-19317
             Project: Flink
          Issue Type: Sub-task
          Components: API / DataStream
            Reporter: Aljoscha Krettek
            Assignee: Aljoscha Krettek


Excerpt from FLIP-134:

{quote}
As described above, event time is the only sensible time characteristic for batch. We therefore propose to chagne the default value of the StreamTimeCharacteristic from ProcessingTime to EventTime. This means the DataStream API programs that were using event time before now just work without manually changing this setting. Processing-time programs will also still work, because using processing-time timers is not dependent on the StreamTimeCharacteristic. DataStream programs that don't set a TimestampAssigner or WatermarkStrategy will also still work if they don't use operations that don't rely on (event-time) timestamps. This is true for both BATCH and STREAMING execution mode.

The only real user-visible change of this is that programs that used the KeyedStream.timeWindow()/DataStream.timeWindow() operation, which is dependent on the StreamTimeCharacteristic will now use event time by default. We don't think this operation is useful because the behaviour can be surprising. We recommend users always use an explicit processing-time window or event-time window.
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