Hi, Sumeet
For "input.b" I think you should aggregate the non-group-key
column[1].
But I am not sure why the "input.c.avg.alias('avg_value')" has resolved
errors. Would you mind giving more detailed error information?
[1]
https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/table/tableApi.html#group-windows
Best,
Guowei
On Mon, Apr 19, 2021 at 2:24 PM Sumeet Malhotra <sumeet.malho...@gmail.com>
wrote:
> Hi,
>
> I have a use case where I'm creating a Tumbling window as follows:
>
> "input" table has columns [Timestamp, a, b, c]
>
> input \
> .window(Tumble.over(lit(10).seconds).on(input.Timestamp).alias("w")) \
> .group_by(col('w'), input.a) \
> .select(
> col('w').start.alias('window_start'),
> col('w').end.alias('window_end'),
> input.b,
> input.c.avg.alias('avg_value')) \
> .execute_insert('MySink') \
> .wait()
>
> This throws an exception that it cannot resolve the fields "b" and "c"
> inside the select statement. If I mention these column names inside the
> group_by() statement as follows:
>
> .group_by(col('w'), input.a, input.b, input.c)
>
> then the column names in the subsequent select statement can be resolved.
>
> Basically, unless the column name is explicitly made part of the
> group_by() clause, the subsequent select() clause doesn't resolve it. This
> is very similar to the example from Flink's documentation here [1]:
> https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/table/tableApi.html#overview--examples,
> where a similar procedure works.
>
> Any idea how I can access columns from the input stream, without having to
> mention them in the group_by() clause? I really don't want to group the
> results by those fields, but they need to be written to the sink eventually.
>
> Thanks,
> Sumeet
>
