[jira] [Updated] (ARROW-9520) [Rust] [DataFusion] Can't alias an aggregate expression

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-9520?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

ASF GitHub Bot updated ARROW-9520:
----------------------------------
    Labels: pull-request-available  (was: )

> [Rust] [DataFusion] Can't alias an aggregate expression
> -------------------------------------------------------
>
>                 Key: ARROW-9520
>                 URL: https://issues.apache.org/jira/browse/ARROW-9520
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Rust - DataFusion
>            Reporter: Jorge Leitão
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> The following test (on execute) fails:
> {code}
>     #[test]
>     fn aggregate_with_alias() -> Result<()> {
>         let results = execute("SELECT c1, COUNT(c2) AS count FROM test GROUP BY c1", 4)?;
>         assert_eq!(field_names(batch), vec!["c1", "count"]);
>         let expected = vec!["0,10", "1,10", "2,10", "3,10"];
>         let mut rows = test::format_batch(&batch);
>         rows.sort();
>         assert_eq!(rows, expected);
>         Ok(())
>     }
> {code}
> The root cause is that, in {{sql::planner}}, we interpret {{COUNT(c2) AS count}} as An {{Expr::Alias}}, which fails the {{is_aggregate_expr}} condition, thus being interpreted as grouped expression instead of an aggregated expression. This raises the Error
> {{General("Projection references non-aggregate values")}}
> The planner could interpret the statement above as two steps: an aggregation followed by a projection. Alternatively, we can allow aliases to be valid aggregation expressions.



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