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https://issues.apache.org/jira/browse/FLINK-25604?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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godfrey he reassigned FLINK-25604:
----------------------------------
Assignee: godfrey he
> Remove useless aggregate function
> ----------------------------------
>
> Key: FLINK-25604
> URL: https://issues.apache.org/jira/browse/FLINK-25604
> Project: Flink
> Issue Type: Sub-task
> Components: Table SQL / Planner
> Reporter: Jing Zhang
> Assignee: godfrey he
> Priority: Minor
>
> We expect useless aggregate call could be removed after projection push down.
> But sometimes, planner is unexpected. For example,
> {code:sql}
> SELECT
> d
> FROM (
> SELECT
> d,
> c,
> row_number() OVER (PARTITION BY d ORDER BY e desc) review_rank
> FROM (
> SELECT e, d, max(f) AS c FROM Table5 GROUP BY e, d)
> )
> WHERE review_rank = 1
> {code}
> The plan is
> {code:java}
> Calc(select=[d], where=[=(w0$o0, 1:BIGINT)])
> +- OverAggregate(partitionBy=[d], orderBy=[e DESC], window#0=[ROW_NUMBER(*)
> AS w0$o0 ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW], select=[e, d, c,
> w0$o0])
> +- Sort(orderBy=[d ASC, e DESC])
> +- Exchange(distribution=[hash[d]])
> +- HashAggregate(isMerge=[true], groupBy=[e, d], select=[e, d,
> Final_MAX(max$0) AS c])
> +- Exchange(distribution=[hash[e, d]])
> +- LocalHashAggregate(groupBy=[e, d], select=[e, d,
> Partial_MAX(f) AS max$0])
> +- Calc(select=[e, d, f])
> +- BoundedStreamScan(table=[[default_catalog,
> default_database, Table5]], fields=[d, e, f, g, h])
> {code}
> In the above sql, max(c) could be removed because it is projected out before
> sink.
>
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