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Soundararajan Velu commented on HIVE-1139: ------------------------------------------ Ning, Aravind, I got this implemented and it looks good so far, I will try uploading the version I have modified after a thorough test, All I did was copy the HashMap implementation into the HashMapWrapper (leaving the existing functionality intact), now HashmapWrapper works exactly like hashmap, but I did not get to test out the serialization issues. will do that and update you guys. I think this should help us in our OOM issue around GroupBy... > 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: Arvind Prabhakar > > 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.