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https://issues.apache.org/jira/browse/FLINK-7548?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16176020#comment-16176020
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Xingcan Cui commented on FLINK-7548:
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Hi [~fhueske] and [~jark], sorry for the late reply.
Honestly, I don't have much experience in real application, but I think the
proposal is quite reasonable. In brief, any (existing or computed) field with
the type {{LONG}} or {{TIMESTAMP}} can be taken as a rowtime field, right? Here
are my thoughts:
1. Considering that the data type should be preserved, it may bring extra logic
if we do that internally. To keep the consistency, I wonder if it's possible to
encapsulate the time into a new {{Rowtime<T>}} type. It exposes two methods,
{{getTime(): Long}} for logical level use and {{getValue(): T}} for physical
level use.
2. Besides, I think the watermark generation should not be bound with rowtime
extraction. Compared with implementing them in a single scan operator (not sure
if I understood correctly), I prefer to generate watermarks in extra operators.
That should be more flexible.
3. I am thinking of a new record number bounded out-of-order generation
strategy. Do you think it will be useful in real applications?
4. I still feel that the machine time is not compatible with the rowtime
watermark generation. Shall we consider getting rid of it?
> 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.
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