Hi,

There's a Flink SQL Cookbook recipe on CURRENT_WATERMARK, I think this
would cover your questions [1].

Best regards,

Martijn

[1]
https://github.com/ververica/flink-sql-cookbook/blob/main/other-builtin-functions/03_current_watermark/03_current_watermark.md

On Fri, 11 Feb 2022 at 16:45, M Singh <mans2si...@yahoo.com> wrote:

> Hi:
>
> The flink docs (
> https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/functions/systemfunctions/)
> indicates that the CURRENT_WATERMARK(rowtime) can return null:
>
> Note that this function can return NULL, and you may have to consider
> this case. For example, if you want to filter out late data you can use:
>
> WHERE
>   CURRENT_WATERMARK(ts) IS NULL
>   OR ts > CURRENT_WATERMARK(ts)
>
>
> I have the following questions that if the table is defined with a
> watermark eg:
>
> CREATE TABLE `MYEVENTS` (
> `name` STRING,
> `event_time` TIMESTAMP_LTZ(3),
>  ...
> WATERMARK FOR event_time AS event_time - INTERVAL '30' SECONDS)
> WITH (...)
>
>
> 1. If we define the water mark as above, will the late events still be
> propagated to a view or table which is selecting from MYEVENTS table:
>
> CREATE TEMPORARY VIEW `ALL_EVENTS` AS
>     SELECT * FROM MYEVENTS;
>
> 2. Can CURRENT_WATERMARK(event_time) still return null ?  If so, what are
> the conditions for returning null ?
>
>
>
> Thanks
>
>
>
>

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