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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #4020: [FLINK-6747] [table] [docs] Time attributes sectio...
Date Tue, 30 May 2017 22:10:06 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4020#discussion_r119223115
  
    --- Diff: docs/dev/table/streaming.md ---
    @@ -39,17 +39,293 @@ Dynamic table
     Time Attributes
     ---------------
     
    -### Event-time
    +Flink supports different notions of *time* in streaming programs.
     
    -* DataStream: Timestamps & WMs required, `.rowtime` (replace attribute or extend
schema)
    -* TableSource: Timestamps & WMs & DefinedRowtimeAttribute
    +- *Processing time* refers to the system time of the machine (also known as "wall-clock
time") that is executing the respective operation.
    +- *Event time* is the time that each individual event occurred on its producing device.
    +- *Ingestion time* is the time that events enter Flink, internally, it is treated similar
to event time.
     
    -{% top %}
    +For more information about time handling in Flink, see the introduction about [Event
Time and Watermarks]({{ site.baseurl }}/dev/event_time.html).
    +
    +Table programs assume that a corresponding time characteristic has been specified for
the streaming environment:
    +
    +<div class="codetabs" markdown="1">
    +<div data-lang="java" markdown="1">
    +{% highlight java %}
    +final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
    +
    +env.setStreamTimeCharacteristic(TimeCharacteristic.ProcessingTime); // default
    +
    +// alternatively:
    +// env.setStreamTimeCharacteristic(TimeCharacteristic.IngestionTime);
    +// env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
    +{% endhighlight %}
    +</div>
    +<div data-lang="scala" markdown="1">
    +{% highlight scala %}
    +val env = StreamExecutionEnvironment.getExecutionEnvironment
    +
    +env.setStreamTimeCharacteristic(TimeCharacteristic.ProcessingTime) //default
    +
    +// alternatively:
    +// env.setStreamTimeCharacteristic(TimeCharacteristic.IngestionTime)
    +// env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)
    +{% endhighlight %}
    +</div>
    +</div>
    +
    +Time-based operations such as [windows]({{ site.baseurl }}/dev/table/tableApi.html) in
both the Table API and SQL require information about the notion of time and its origin. Therefore,
tables can offer *logical time attributes* for indicating time and accessing corresponding
timestamps in table programs.
    --- End diff --
    
    links on "Table API" and "SQL" for the respective sections in the documentation.


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