Hi Hequn,
If limit n is not supported in streaming, how to solve top n problem in
stream scenario?
Best
Henry
> 在 2018年9月28日，上午12:03，Hequn Cheng <[email protected]> 写道：
>
> Hi Henry,
>
> Currently, Order By is supported in Streaming&Batch while Limit is only
> supported in Batch. Another thing to be noted is, for Order by, the result of
> streaming queries must be primarily sorted on an ascending time attribute[1].
>
> [1]
> https://ci.apache.org/projects/flink/flink-docs-master/dev/table/sql.html#orderby--limit
>
> <https://ci.apache.org/projects/flink/flink-docs-master/dev/table/sql.html#orderby--limit>
>
>
>
> On Thu, Sep 27, 2018 at 9:05 PM 徐涛 <[email protected]
> <mailto:[email protected]>> wrote:
> Hi,
> I want a top n result on each hop window result, but some error throws
> out when I add the order by sentence or the limit sentence, so how do I
> implement such case ?
> Thanks a lot.
>
> SELECT
> trackId as id,track_title as description, count(*) as cnt
> FROM
> play
> WHERE
> appName='play.statistics.trace'
> GROUP BY
> HOP(started_at_ts, INTERVAL '1' SECOND, INTERVAL '5'
> MINUTE),trackId,track_title
> ORDER BY
> cnt desc
> LIMIT 10
>
> FlinkLogicalSort(sort0=[$2], dir0=[DESC])
> FlinkLogicalWindowAggregate(group=[{1, 2}], cnt=[COUNT()])
> FlinkLogicalCalc(expr#0..4=[{inputs}],
> expr#5=[_UTF-16LE'play.statistics.trace'], expr#6=[=($t0, $t5)],
> started_at_ts=[$t4], trackId=[$t1], track_title=[$t2], $condition=[$t6])
> FlinkLogicalNativeTableScan(table=[[play]])
>
> This exception indicates that the query uses an unsupported SQL feature.
> Please check the documentation for the set of currently supported SQL
> features.
> at
> org.apache.flink.table.api.TableEnvironment.runVolcanoPlanner(TableEnvironment.scala:275)
> at
> org.apache.flink.table.api.StreamTableEnvironment.optimize(StreamTableEnvironment.scala:845)
> at
> org.apache.flink.table.api.StreamTableEnvironment.translate(StreamTableEnvironment.scala:892)
> at
> org.apache.flink.table.api.StreamTableEnvironment.writeToSink(StreamTableEnvironment.scala:344)
> at
> org.apache.flink.table.api.TableEnvironment.insertInto(TableEnvironment.scala:786)
> at
> org.apache.flink.table.api.TableEnvironment.sqlUpdate(TableEnvironment.scala:723)
> at
> org.apache.flink.table.api.TableEnvironment.sqlUpdate(TableEnvironment.scala:683)
>
> Best
> Henry
