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https://issues.apache.org/jira/browse/TAJO-1058?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14159310#comment-14159310
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Hyunsik Choi commented on TAJO-1058:
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Off-heap hash table should keep aggregation contexts into off-heap memory
space. For this, it requires a different kind function implementation.
TAJO-1092 will resolve this problem.
> Implement off-heap hash table for hash aggregation
> --------------------------------------------------
>
> Key: TAJO-1058
> URL: https://issues.apache.org/jira/browse/TAJO-1058
> Project: Tajo
> Issue Type: Sub-task
> Components: physical operator
> Reporter: Hyunsik Choi
> Assignee: Hyunsik Choi
> Labels: block_iteration
> Fix For: block_iteration
>
>
> See the title.
> Currently, we use HashMap for hash aggregation. It causes GC overheads when
> the number of distinct hash keys is over tens of millions. We need to
> implement an alternative to the current implementation. This implementation
> should consider block iteration addressed in TAJO-1041.
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