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[jira] [Created] (FLINK-10875) Add `toTableWithTimestamp` method in `DataStreamConversions`

sunjincheng created FLINK-10875:

             Summary: Add `toTableWithTimestamp` method in `DataStreamConversions`
                 Key: FLINK-10875
                 URL: https://issues.apache.org/jira/browse/FLINK-10875
             Project: Flink
          Issue Type: Improvement
          Components: Table API & SQL
            Reporter: sunjincheng
            Assignee: sunjincheng
             Fix For: 1.7.1

Currently we convert a `DataStream` to a `Table` by  `DataStreamConversions#toTable`, e.g.:
// Without TimeAttribute
val stream = env.fromCollection(...)
val tab = stream.toTable(tEnv, 'a, 'b, 'c)
val result = tab.select('a, 'b)

// With TimeAttribute
val stream = env.fromCollection(...).assignTimestampsAndWatermarks(...)
val tab = stream.toTable(tEnv, 'a, 'b, 'c, 'ts.rowtime)
val result = tab.window(Session withGap 5.milli on 'ts as 'w)
I think the fieldNames parameter in the `toTable` method is reasonable in the conversion without the time attribute, because the fieldNames will actually correspond to the fields of the physical table, but when applied to the conversion with the time attribute, the time attribute column is silently added to the table. This feeling is very Magical, so I recommend adding a method that allows the user to display the time attribute added to the physical table: `toTableWithTimestamp`, which is automatically named to the time attribute column named by user input and TimeCharacteristic, eg:
val table = stream.toTableWithTimestamp(tEnv, 'count, 'size, 'name, 'ts)
  .window(Tumble over 2.rows on 'ts as 'w)
In the example above the flink will mark `ts` ad a `RowtimeAttribute`.

What do you think ? 

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