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https://issues.apache.org/jira/browse/FLINK-3941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15297806#comment-15297806
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ASF GitHub Bot commented on FLINK-3941:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2025#discussion_r64338066
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/nodes/dataset/DataSetUnion.scala
---
@@ -69,7 +73,7 @@ class DataSetUnion(
rows + metadata.getRowCount(child)
}
- planner.getCostFactory.makeCost(rowCnt, 0, 0)
+ planner.getCostFactory.makeCost(if (all) rowCnt else rowCnt * 0.1, 0,
0)
--- End diff --
The cost for union should be higher than for union all. Also, `rowCnt` is
the number of rows processed, not the result size.
How about this?
```
planner.getCostFactory.makeCost(
rowCnt,
if (all) 0 else, rowCnt,
if (all) 0 else rowCnt)
```
> Add support for UNION (with duplicate elimination)
> --------------------------------------------------
>
> Key: FLINK-3941
> URL: https://issues.apache.org/jira/browse/FLINK-3941
> Project: Flink
> Issue Type: New Feature
> Components: Table API
> Affects Versions: 1.1.0
> Reporter: Fabian Hueske
> Assignee: Yijie Shen
> Priority: Minor
>
> Currently, only UNION ALL is supported by Table API and SQL.
> UNION (with duplicate elimination) can be supported by applying a
> {{DataSet.distinct()}} after the union on all fields. This issue includes:
> - Extending {{DataSetUnion}}
> - Relaxing {{DataSetUnionRule}} to translated non-all unions.
> - Extend the Table API with union() method.
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