[
https://issues.apache.org/jira/browse/FLINK-7548?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16181234#comment-16181234
]
Fabian Hueske commented on FLINK-7548:
--------------------------------------
I think there might be a misunderstanding of the
{{TimestampsAndPeriodicWatermarksOperator}}.
bq. About my last question, I actually refer to the
TimestampsAndPeriodicWatermarksOperator. Here, the "periodic" refers to
proctime. Considering the time systems for the rowtime and the proctime may not
be synchronized (i.e., they get different speeds), could we consider providing
a "rowtime periodic" assigner?
The assigner does not emit watermarks that have a processing time _value_ but
only in regular time intervals that are based on processing time.
So, whenever the interval has passed, the operator asks the
{{AssignerWithPeriodicWatermarks}} to return the current watermark. The
watermark should based on the event-time timestamps that the
{{AssignerWithPeriodicWatermarks}} observed (in fact this depends on the
implementation of the assigner). So the value of the watermarks is based on
event-time but the interval in which the watermarks are generated is not.
AFAIK, this is the most commonly used watermark generation strategy. So it
seems to suit many users.
> Support watermark generation for TableSource
> --------------------------------------------
>
> Key: FLINK-7548
> URL: https://issues.apache.org/jira/browse/FLINK-7548
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Reporter: Jark Wu
>
> As discussed in FLINK-7446, currently the TableSource only support to define
> rowtime field, but not support to extract watermarks from the rowtime field.
> We can provide a new interface called {{DefinedWatermark}}, which has two
> methods {{getRowtimeAttribute}} (can only be an existing field) and
> {{getWatermarkGenerator}}. The {{DefinedRowtimeAttribute}} will be marked
> deprecated.
> How to support periodic and punctuated watermarks and support some built-in
> strategies needs further discussion.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
