[
https://issues.apache.org/jira/browse/HIVE-20153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16542550#comment-16542550
]
Gopal V commented on HIVE-20153:
--------------------------------
>From a quick look, it looks like they are hashmaps with 0 items.
{code}
@Override
public void reset(AggregationBuffer agg) throws HiveException {
((CountAgg) agg).value = 0;
((CountAgg) agg).uniqueObjects = new HashSet<ObjectInspectorObject>();
}
{code}
> Count and Sum UDF consume more memory in Hive 2+
> ------------------------------------------------
>
> Key: HIVE-20153
> URL: https://issues.apache.org/jira/browse/HIVE-20153
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Affects Versions: 2.3.2
> Reporter: Szehon Ho
> Assignee: Aihua Xu
> Priority: Major
> Attachments: Screen Shot 2018-07-12 at 6.41.28 PM.png
>
>
> While playing with Hive2, we noticed that queries with a lot of count() and
> sum() aggregations run out of memory on Hadoop side where they worked before
> in Hive1.
> In many queries, we have to double the Mapper Memory settings (in our
> particular case mapreduce.map.java.opts from -Xmx2000M to -Xmx4000M), it
> makes it not so easy to upgrade to Hive 2.
> Taking heap dump, we see one of the main culprit is the field 'uniqueObjects'
> in GeneraicUDAFSum and GenericUDAFCount, which was added to support Window
> functions.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
