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https://issues.apache.org/jira/browse/FLINK-7548?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16209327#comment-16209327
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Kurt Young commented on FLINK-7548:
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Actually I was thinking that when projections are pushed down, we should keep
the TableSource's schema unchanged. For example, when we want to read a csv
file, the schema of the file is somewhat fixed. Whether we want to read all
fields or some selected fields from that file will not affect the schema of the
table. I think we should keep the schema fixed and change the result type after
projection push down.
But this depends on how we see or define what the {{schema}} of a
{{TableSource}}. If the schema changes with field projections, it makes no
differences with current result type inference. What do you think?
> Support watermark generation for TableSource
> --------------------------------------------
>
> Key: FLINK-7548
> URL: https://issues.apache.org/jira/browse/FLINK-7548
> Project: Flink
> Issue Type: Improvement
> Components: Table API & SQL
> Reporter: Jark Wu
> Assignee: Fabian Hueske
> Priority: Blocker
> Fix For: 1.4.0
>
>
> 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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