Jark Wu created FLINK-15979:
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Summary: Fix the merged count is not accurate in
CountDistinctWithMerge
Key: FLINK-15979
URL: https://issues.apache.org/jira/browse/FLINK-15979
Project: Flink
Issue Type: New Feature
Components: Table SQL / Legacy Planner
Reporter: Jark Wu
As discussed in the user ML:
https://lists.apache.org/thread.html/rc4b06c9931656c94dc993b124da3ff00f04099e41201c64788936c24%40%3Cuser.flink.apache.org%3E.
The current implementation of
{{org.apache.flink.table.runtime.utils.JavaUserDefinedAggFunctions.CountDistinctWithMerge#merge}}
in old planner is not correct which will have a wrong merged count.
The test
(org.apache.flink.table.runtime.stream.table.GroupWindowITCase#testEventTimeSessionGroupWindowOverTime)
which uses this UDAF can't expose the bug because there are no distinct values
in the test data.
The class {{CountDistinctWithMerge}} is a testing implementation which is not a
critical problem. Blink planner has a correct implementation:
https://github.com/apache/flink/blob/master/flink-table/flink-table-planner-blink/src/test/java/org/apache/flink/table/planner/plan/utils/JavaUserDefinedAggFunctions.java#L369
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