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https://issues.apache.org/jira/browse/HIVE-9277?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wei Zheng updated HIVE-9277:
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Attachment: HIVE-9277.02.patch
Uploading 2nd patch for testing
> Hybrid Hybrid Grace Hash Join
> -----------------------------
>
> Key: HIVE-9277
> URL: https://issues.apache.org/jira/browse/HIVE-9277
> Project: Hive
> Issue Type: New Feature
> Components: Physical Optimizer
> Reporter: Wei Zheng
> Assignee: Wei Zheng
> Labels: join
> Attachments: HIVE-9277.01.patch, HIVE-9277.02.patch,
> High-leveldesignforHybridHybridGraceHashJoinv1.0.pdf
>
>
> We are proposing an enhanced hash join algorithm called “hybrid hybrid grace
> hash join”. We can benefit from this feature as illustrated below:
> o The query will not fail even if the estimated memory requirement is
> slightly wrong
> o Expensive garbage collection overhead can be avoided when hash table grows
> o Join execution using a Map join operator even though the small table
> doesn't fit in memory as spilling some data from the build and probe sides
> will still be cheaper than having to shuffle the large fact table
> The design was based on Hadoop’s parallel processing capability and
> significant amount of memory available.
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