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https://issues.apache.org/jira/browse/FLINK-3971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15324684#comment-15324684
]
ASF GitHub Bot commented on FLINK-3971:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2049#discussion_r66638155
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/runtime/aggregate/AvgAggregate.scala
---
@@ -66,51 +66,63 @@ abstract class IntegralAvgAggregate[T] extends
AvgAggregate[T] {
def doPrepare(value: Any, partial: Row): Unit
}
-class ByteAvgAggregate extends IntegralAvgAggregate[Byte] {
+class ByteAvgAggregate[T] extends IntegralAvgAggregate[T] {
--- End diff --
I think it would be cleaner to keep the `Byte` type parameter.
How about we add an abstract method `def doEvaluate(buffer: Row): Any` to
`IntegralAvgAggregate`.
The subclasses of `IntegralAvgAggregate` implement `doEvaluate` like
`ByteAvgAggregate`:
```
override def doEvaluate(buffer: Row): Any = {
val bufferSum = buffer.productElement(partialSumIndex).asInstanceOf[Long]
val bufferCount =
buffer.productElement(partialCountIndex).asInstanceOf[Long]
if (bufferCount == 0L) {
null
} else {
(bufferSum / bufferCount).toByte
}
}
```
and return an `Any` which is casted to `T` by
`IntegralAvgAggregate.evaluate()` as follows:
```
override def evaluate(buffer: Row): T = {
doEvaluate(buffer).asInstanceOf[T]
}
```
Same for the `FloatingAvgAggregate` and its subclasses.
> Aggregates handle null values incorrectly.
> ------------------------------------------
>
> Key: FLINK-3971
> URL: https://issues.apache.org/jira/browse/FLINK-3971
> Project: Flink
> Issue Type: Bug
> Components: Table API
> Affects Versions: 1.1.0
> Reporter: Fabian Hueske
> Assignee: GaoLun
> Priority: Critical
> Fix For: 1.1.0
>
>
> Table API and SQL aggregates are supposed to ignore null values, e.g.,
> {{sum(1,2,null,4)}} is supposed to return {{7}}.
> There current implementation is correct if at least one valid value is
> present however, is incorrect if only null values are aggregated. {{sum(null,
> null, null)}} should return {{null}} instead of {{0}}
> Currently only the Count aggregate handles the case of null-values-only
> correctly.
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