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https://issues.apache.org/jira/browse/FLINK-3971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15324686#comment-15324686
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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_r66638439
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/runtime/aggregate/MaxAggregate.scala
---
@@ -48,8 +48,16 @@ abstract class MaxAggregate[T](implicit ord:
Ordering[T]) extends Aggregate[T] {
override def merge(intermediate: Row, buffer: Row): Unit = {
val partialValue =
intermediate.productElement(maxIndex).asInstanceOf[T]
val bufferValue = buffer.productElement(maxIndex).asInstanceOf[T]
- val max: T = if (ord.compare(partialValue, bufferValue) > 0)
partialValue else bufferValue
- buffer.setField(maxIndex, max)
+ if (partialValue == null && bufferValue == null) {
+ buffer.setField(maxIndex, null.asInstanceOf[T])
--- End diff --
When setting a field in a `Row` to `null` we do not need to cast.
> 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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