Hi Henry,
praiseAggr is an append table, so it contains "100,101,102,100,101,103,100".
1. if you change your sql to s"SELECT article_id FROM praise GROUP BY
article_id", the answer is "101,102,103"
2. if you change your sql to s"SELECT last_value(article_id) FROM praise",
the answer is "100"
Best, Hequn
On Tue, Aug 21, 2018 at 8:52 PM, 徐涛 <happydexu...@gmail.com> wrote:
> Hi Fabian,
> Thanks for your response. This question puzzles me for quite a long time.
> If the praiseAggr has the following value:
> window-1 100,101,102
> window-2 100,101,103
> window-3 100
>
> the last time the article table joins praiseAggr, which of the following
> value does praiseAggr table has?
> 1— 100,101,102,100,101,103,100 collect all the element of all
> the window
> 2— 100 the element of the latest window
> 3— 101,102,103 the distinct value of all the window
>
>
> Best,
> Henry
>
>
> 在 2018年8月21日，下午8:02，Fabian Hueske <fhue...@gmail.com> 写道：
>
> Hi,
>
> The semantics of a query do not depend on the way that it is used.
> praiseAggr is a table that grows by one row per second and article_id. If
> you use that table in a join, the join will fully materialize the table.
> This is a special case because the same row is added multiple times, so
> the state won't grow that quickly, but the performance will decrease
> because for each row from article will join with multiple (a growing
> number) of rows from praiseAggr.
>
> Best, Fabian
>
> 2018-08-21 12:19 GMT+02:00 徐涛 <happydexu...@gmail.com>:
>
>> Hi All,
>> var praiseAggr = tableEnv.sqlQuery(s"SELECT article_id FROM praise GROUP
>> BY HOP(updated_time, INTERVAL '1' SECOND,INTERVAL '3' MINUTE) , article_id"
>> )
>> tableEnv.registerTable("praiseAggr", praiseAggr)
>>
>> var finalTable = tableEnv.sqlQuery(*s**”**SELECT 1 FROM article a join
>> praiseAggr p on a.article_id=p.article_id" *)
>> tableEnv.registerTable("finalTable", finalTable)
>>
>> I know that praiseAggr, if written to sink, is append mode , so if a
>> table joins praiseAggr, what the table “see”, is a table contains the
>> latest value, or a table that grows larger and larger? If it is the later,
>> will it introduce performance problem?
>> Thanks a lot.
>>
>>
>> Best,
>> Henry
>>
>
>
>
