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Ning Zhang commented on HIVE-1139: ---------------------------------- GroupByOperator uses HashMap's size() and iterator() API, which is not supported by HashMapWrapper right now. We should extended HashMapWrapper to support those. > GroupByOperator sometimes throws OutOfMemory error when there are too many > distinct keys > ---------------------------------------------------------------------------------------- > > Key: HIVE-1139 > URL: https://issues.apache.org/jira/browse/HIVE-1139 > Project: Hadoop Hive > Issue Type: Bug > Reporter: Ning Zhang > Assignee: Ning Zhang > > When a partial aggregation performed on a mapper, a HashMap is created to > keep all distinct keys in main memory. This could leads to OOM exception when > there are too many distinct keys for a particular mapper. A workaround is to > set the map split size smaller so that each mapper takes less number of rows. > A better solution is to use the persistent HashMapWrapper (currently used in > CommonJoinOperator) to spill overflow rows to disk. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.