Hi,

*> Could you give an example that the query has a unique key?*

Consider the following sql:

SELECT a, SUM(b) as d
> FROM Orders
> GROUP BY a


The result table contains unique key of a.  A document about Streaming
Concepts[1] may be helpful for you.

*> What is the mechanism flink infer which field is the unique key(s)?*

Currently(flink-1.6.0), flink sql generate unique keys only from group by
and the unique keys info can be passed to the downstream operators, for
example the SELECT.

*Implement a RetractStreamTableSink*

Since outer joins output update data without unique keys, you can use a
RetractTableSink to output data. There are some documents about implement a
table sink[2].

Best, Hequn

[1]
https://ci.apache.org/projects/flink/flink-docs-master/dev/table/streaming.html#streaming-concepts
[2]
https://ci.apache.org/projects/flink/flink-docs-master/dev/table/sourceSinks.html#define-a-tablesink


On Sat, Aug 11, 2018 at 6:02 AM, 徐涛 <happydexu...@gmail.com> wrote:

> Hi Fabian,
> Could you give an example that the query has a unique key?
> What is the mechanism flink infer which field is the unique key(s)?
>         Thanks a lot!
>
> Best, Henry
>
>
> 在 2018年8月11日,上午5:21,Fabian Hueske <fhue...@gmail.com> 写道:
>
> Hi Henry,
>
> The problem is that the table that results from the query does not have a
> unique key.
> You can only use an upsert sink if the table has a (composite) unique key.
> Since this is not the case, you cannot use upsert sink.
> However, you can implement a StreamRetractionTableSink which allows to
> write any kind of Table (append-only/update, keyed/non-keyed) to an
> external system.
>
> Best, Fabian
>
> 2018-08-10 17:06 GMT+02:00 徐涛 <happydexu...@gmail.com>:
>
>> Hi All,
>> I am using flink 1.6 to generate some realtime programs. I want to write
>> the output to table sink, the code is as below. At first I use append table
>> sink, which error message tells me that I should use upsert table sink, so
>> I write one. But still another error “Caused by:
>> org.apache.flink.table.api.TableException: UpsertStreamTableSink
>> requires that Table has a full primary keys if it is updated.” comes
>> out,which blocks me. My questions is how to modify a table keys in this
>> scenario? I also check the exception stack, and found that the system infer
>> the keys field by
>> val tableKeys: Option[Array[String]] = 
>> UpdatingPlanChecker.getUniqueKeyFields(optimizedPlan),
>> I wonder how to make the function return value ?
>> Thanks a lot !!!
>>
>>     var praise = tableEnv.sqlQuery(s"SELECT article_id,hll(uid) as PU FROM 
>> praise GROUP BY HOP(updated_time, INTERVAL '1' MINUTE,INTERVAL '3' 
>> DAY),article_id" )
>>     tableEnv.registerTable("praiseAggr", praise)
>>
>>     var comment = tableEnv.sqlQuery(s"SELECT article_id,hll(from_uid) as CU 
>> FROM comment GROUP BY HOP(updated_time, INTERVAL '1' MINUTE,INTERVAL '3' 
>> DAY),article_id" )
>>     tableEnv.registerTable("commentAggr", comment)
>>
>>     var reader = tableEnv.sqlQuery(s"SELECT article_id,hll(uid) as RU FROM 
>> reader GROUP BY HOP(updated_time, INTERVAL '1' MINUTE,INTERVAL '3' 
>> DAY),article_id" )
>>     tableEnv.registerTable("readerAggr", reader)
>>
>>     var finalTable = tableEnv.sqlUpdate(s"insert into "+ sinkTableName + " " 
>> +  " SELECT p.article_id,p.PU,c.CU,r.RU from praiseAggr p FULL OUTER JOIN 
>> commentAggr c on p.article_id=c.article_id FULL OUTER JOIN readerAggr r on 
>> c.article_id=r.article_id")
>>
>>
>>
>>
>> Thank,
>> Henry Xu
>>
>
>
>

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