Hi RKandoji~
Could you provide more info about your poc environment?
Stream or batch? Flink planner or blink planner?
AFAIK, blink planner has done some optimization to deal such duplicate task for
one same query. You can have a try with blink planner :
https://ci.apache.org/projects/flink/flink-docs-master/dev/table/common.html#create-a-tableenvironment
<https://ci.apache.org/projects/flink/flink-docs-master/dev/table/common.html#create-a-tableenvironment>
Best,
Terry Wang
> 2019年12月30日 03:07，RKandoji <rkand...@gmail.com> 写道：
>
> Hi Team,
>
> I'm doing a POC with flink to understand if it's a good fit for my use case.
>
> As part of the process, I need to filter duplicate items and created below
> query to get only the latest records based on timestamp. For instance, I have
> "Users" table which may contain multiple messages for the same "userId". So I
> wrote below query to get only the latest message for a given "userId"
>
> Table uniqueUsers = tEnv.sqlQuery("SELECT * FROM Users WHERE (userId,
> userTimestamp) IN (SELECT userId, MAX(userTimestamp) FROM Users GROUP BY
> userId)");
>
> The above query works as expected and contains only the latest users based on
> timestamp.
>
> The issue is when I use "uniqueUsers" table multiple times in a JOIN
> operation, I see multiple tasks in the flink dashboard for the same query
> that is creating "uniqueUsers" table. It is simply creating as many tasks as
> many times I'm using the table.
>
> Below is the JOIN query.
> tEnv.registerTable("uniqueUsersTbl", uniqueUsers);
> Table joinOut = tEnv.sqlQuery("SELECT * FROM Car c
> LEFT JOIN uniqueUsersTbl aa ON
> c.userId = aa.userId
> LEFT JOIN uniqueUsersTbl ab ON
> c.ownerId = ab.userId
> LEFT JOIN uniqueUsersTbl ac ON
> c.sellerId = ac.userId
> LEFT JOIN uniqueUsersTbl ad ON
> c.buyerId = ad.userId");
>
> Could someone please help me understand how I can avoid these duplicate tasks?
>
>
> Thanks,
> R Kandoji
