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https://issues.apache.org/jira/browse/FLINK-8325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16332417#comment-16332417
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ASF GitHub Bot commented on FLINK-8325:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/5241#discussion_r162642637
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/dataset/DataSetAggregate.scala
---
@@ -157,6 +158,7 @@ class DataSetAggregate(
} else {
inputDS
.reduceGroup(finalAgg)
+ .mapPartition(emptyProcessMapPartition.get)
--- End diff --
I thought about this again.
I think we should extend `DataSetFinalAggFunction` to also implement
`MapPartitionFunction` similar to the `DataSetPreAggFunction`. The
`GroupReduceFunction.reduceGroup()` method and the
`MapPartitionFunction.mapPartition()` function share the same code. For the
grouped aggregation, we use `reduceGroup(function)` and for the non-grouped
aggregation we use `mapPartition(function).setParallelism(1)`. Setting the
parallelism is important here.
That way we avoid an additional function and its a cleaner design.
> Add COUNT AGG support constant parameter, i.e. COUNT(*), COUNT(1)
> ------------------------------------------------------------------
>
> Key: FLINK-8325
> URL: https://issues.apache.org/jira/browse/FLINK-8325
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Affects Versions: 1.5.0
> Reporter: sunjincheng
> Assignee: sunjincheng
> Priority: Major
>
> COUNT(1) with Group Window, always output 0.
> e.g.
> DATA:
> {code}
> val data = List(
> (1L, 1, "Hi"),
> (2L, 2, "Hello"),
> (4L, 2, "Hello"),
> (8L, 3, "Hello world"),
> (16L, 3, "Hello world"))
> {code}
> SQL:
> {code}
> SELECT b, COUNT(1) FROM MyTable GROUP BY Hop(proctime, interval '0.001'
> SECOND, interval '0.002' SECOND),b
> {code}
> OUTPUT:
> {code}
> 1,0,1,
> 1,0,1,
> 2,0,1,
> 2,0,1,
> 2,0,2,
> 3,0,1,
> 3,0,1
> {code}
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