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https://issues.apache.org/jira/browse/FLINK-4604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15667697#comment-15667697
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Timo Walther commented on FLINK-4604:
-------------------------------------
I looked into the problem. If you take a look at
{{AggregateReduceFunctionsRule}} (e.g. line 354), you see that the null literal
is created with no type/the {{NULL}} type. We currently do not support this
type. Either we replace this and similar lines with
{{rexBuilder.makeNullLiteral(sumZeroRef.getType().getSqlTypeName())}} to give
it a type or we create a new type but I don't know how we want to represent it
so far.
> 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
> Attachments: 1.jpg
>
>
> 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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