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https://issues.apache.org/jira/browse/FLINK-21225?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17276561#comment-17276561
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Jane Chan commented on FLINK-21225:
-----------------------------------
Hi [~jark] and [~twalthr], I checked the case at
[https://github.com/twalthr/flink/tree/FLINK-21225] and found that besides the
distinct flag is set to false, {{OverConvertRule}} could not make rex call for
children expression like {{distinct(avg/count/sum(field))}}, thus cause
{{ExpressionConverter#visit}} throwing exception that "Unknown call expression:
avg(field)". And I'd like to fix this issue.
> OverConvertRule does not consider distinct
> ------------------------------------------
>
> Key: FLINK-21225
> URL: https://issues.apache.org/jira/browse/FLINK-21225
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Reporter: Timo Walther
> Priority: Major
>
> We don't support OVER window distinct aggregates in Table API. Even though
> this is explicitly documented:
> https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/table/tableApi.html#aggregations
> {code}
> // Distinct aggregation on over window
> Table result = orders
> .window(Over
> .partitionBy($("a"))
> .orderBy($("rowtime"))
> .preceding(UNBOUNDED_RANGE)
> .as("w"))
> .select(
> $("a"), $("b").avg().distinct().over($("w")),
> $("b").max().over($("w")),
> $("b").min().over($("w"))
> );
> {code}
> The distinct flag is set to false in {{OverConvertRule}}.
> See also
> http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Unknown-call-expression-avg-amount-when-use-distinct-in-Flink-Thanks-td40905.html
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