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https://issues.apache.org/jira/browse/FLINK-40344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18103327#comment-18103327
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Bettle commented on FLINK-40344:
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Hi, I’d like to work on this issue as my first contribution to Apache Flink. I
plan to add a focused Table API test for computed grouping expressions and
investigate mapping the selected grouping expression to the corresponding
aggregate output field. Could a committer please confirm the approach and
assign the issue to me? Thanks!
> Computed grouping expressions cannot be selected in Table API aggregations
> --------------------------------------------------------------------------
>
> Key: FLINK-40344
> URL: https://issues.apache.org/jira/browse/FLINK-40344
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / API
> Affects Versions: 1.10.0
> Reporter: Liu Liu
> Priority: Minor
>
> Selecting a computed grouping expression from a grouped Table fails even when
> the same expression is used as the grouping key.
> For example:
> {code:java}
> import org.apache.flink.table.api.Expression;
> import org.apache.flink.table.api.Table;
> import static org.apache.flink.table.api.Expressions.$;
> Expression key = $("v").isGreater(10);
> Table result =
> table.groupBy(key)
> .select(key, $("v").count().as("n"));
> {code}
> This raises a ValidationException because field "v" cannot be resolved after
> aggregation. The query should succeed and return the computed Boolean
> grouping key followed by the count. The equivalent SQL query works correctly.
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