lincoln-lil opened a new pull request, #27022:
URL: https://github.com/apache/flink/pull/27022

   ## What is the purpose of the change
   As reported in https://issues.apache.org/jira/browse/CALCITE-7192, the 
following query may produce wrong result:
   ```sql
   SELECT STDDEV_POP(salary) FILTER (WHERE salary > 1000) FROM employees;
   ```
   the decomposition for STDDEV_POP will be:
   ```
   SQRT((SUM(x * x) - SUM(x) * SUM(x) / COUNT(x))/ COUNT(x))
   ```
   for the above example, the `SUM(salary * salary)` lost the filter `salary > 
1000`.  The fix itself is very simple.
   
   ## Brief change log
   Fix AggregateReduceFunctionsRule and add corresponding tests
   
   ## Verifying this change
   Newly added rule test AggregateReduceFunctionsRuleTest
   
   ## Does this pull request potentially affect one of the following parts:
     - Dependencies (does it add or upgrade a dependency): (no)
     - The public API, i.e., is any changed class annotated with 
@Public(Evolving): (no)
     - The serializers: (no )
     - The runtime per-record code paths (performance sensitive): (no)
     - Anything that affects deployment or recovery: JobManager (and its 
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
     - The S3 file system connector: (no)
   
   ## Documentation
     - Does this pull request introduce a new feature? (no)


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