[jira] [Updated] (FLINK-38400) STDDEV/VAR function with FILTER condition may cause wrong result

["lincoln lee (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-38400?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

lincoln lee updated FLINK-38400:
--------------------------------
    Fix Version/s:     (was: 1.20.4)

> STDDEV/VAR function with FILTER condition may cause wrong result
> ----------------------------------------------------------------
>
>                 Key: FLINK-38400
>                 URL: https://issues.apache.org/jira/browse/FLINK-38400
>             Project: Flink
>          Issue Type: Bug
>    Affects Versions: 1.20.2, 2.1.0
>            Reporter: lincoln lee
>            Assignee: lincoln lee
>            Priority: Major
>             Fix For: 2.2.0, 2.1.1
>
>
> As reported in https://issues.apache.org/jira/browse/CALCITE-7192, the following query may produce wrong result:
> {code:java}
> SELECT STDDEV_POP(salary) FILTER (WHERE salary > 1000) FROM employees;
> {code}
> the decomposition for STDDEV_POP will be:
> {code:java}
> SQRT((SUM(x * x) - SUM(x) * SUM(x) / COUNT(x))/ COUNT(x))
> {code}
> for the above example, the `SUM(salary * salary)` lost the filter `salary > 1000`.
>  
> *Impact*
> This affects all functions that use the `reduceStddev` method:
> *STDDEV_POP FILTER (WHERE condition)* 
> *STDDEV_SAMP FILTER (WHERE condition)*
> *VAR_POP FILTER (WHERE condition)* 
> *VAR_SAMP FILTER (WHERE condition)*
> Before we bump up to calcite 1.41.0, we should port the fix first.
>  



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