[jira] [Commented] (FLINK-3850) Add forward field annotations to DataSet operators generated by the Table API

["Fabian Hueske (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-3850?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15435668#comment-15435668 ] 

Fabian Hueske commented on FLINK-3850:
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Sorry for the very long delay [~ram_krish]. I was gone for a while.
You can certainly work on this. I would recommend to first read the documentation about semantic annotations. They can significantly improve the performance if used correctly, but if they are incorrectly applied, the result might be invalid. So one has to be careful ;-)

> Add forward field annotations to DataSet operators generated by the Table API
> -----------------------------------------------------------------------------
>
>                 Key: FLINK-3850
>                 URL: https://issues.apache.org/jira/browse/FLINK-3850
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API & SQL
>            Reporter: Fabian Hueske
>
> The DataSet API features semantic annotations [1] to hint the optimizer which input fields an operator copies. This information is valuable for the optimizer because it can infer that certain physical properties such as partitioning or sorting are not destroyed by user functions and thus generate more efficient execution plans.
> The Table API is built on top of the DataSet API and generates DataSet programs and code for user-defined functions. Hence, it knows exactly which fields are modified and which not. We should use this information to automatically generate forward field annotations and attach them to the operators. This can help to significantly improve the performance of certain jobs.
> [1] https://ci.apache.org/projects/flink/flink-docs-release-1.0/apis/batch/index.html#semantic-annotations



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