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https://issues.apache.org/jira/browse/FLINK-3850?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15902051#comment-15902051
]
ASF GitHub Bot commented on FLINK-3850:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3040#discussion_r105014912
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/dataset/DataSetAggregate.scala
---
@@ -125,11 +126,25 @@ class DataSetAggregate(
.name(aggOpName)
}
else {
+ //Forward all fields at conversion
+ val inputInfo = mappedInput.getType
--- End diff --
PR #3472 will remove the preparing mapper but add a `GroupCombineFunction`.
For both, the combiner and the reducer, we need to forward the fields on which
is grouped because these are not modified but just forwarded.
> 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
> Assignee: Nikolay Vasilishin
>
> 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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