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https://issues.apache.org/jira/browse/FLINK-4604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15551706#comment-15551706
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Timo Walther commented on FLINK-4604:
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Your implementation looks good so far. The output of
{{BatchTableEnvironment#translate}} should actually be a tree of
{{DataSetAggregate}}, {{DataSetCalc}} nodes. Are you using {{explain}} to get
the plan above? It might only print the logical plan. You can have a look at
{{ExpressionReductionTest}} how you can get the optimized plan. This will be
easier when https://github.com/apache/flink/pull/2595 is merged.
> Add support for standard deviation/variance
> -------------------------------------------
>
> Key: FLINK-4604
> URL: https://issues.apache.org/jira/browse/FLINK-4604
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Timo Walther
> Assignee: Anton Mushin
>
> Calcite's {{AggregateReduceFunctionsRule}} can convert SQL {{AVG, STDDEV_POP,
> STDDEV_SAMP, VAR_POP, VAR_SAMP}} to sum/count functions. We should add, test
> and document this rule.
> If we also want to add this aggregates to Table API is up for discussion.
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