Github user twalthr commented on a diff in the pull request:
https://github.com/apache/flink/pull/4585#discussion_r138888586
--- Diff: flink-core/pom.xml ---
@@ -80,6 +80,13 @@ under the License.
<!-- managed version -->
</dependency>
+ <!-- For multiset -->
+ <dependency>
+ <groupId>org.apache.commons</groupId>
--- End diff --
We should not add additional dependencies to Flink just because of a new
data type. There is also no reason behind choosing this library. Couldn't we
not just use a usual Java Map? Otherwise I would propose to add class for our
own type like we did it for `org.apache.flink.types.Row`. Calcite is using
`List`, which is not very nice, but would also work.
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