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From "Mostafa Mokhtar (JIRA)" <>
Subject [jira] [Updated] (HIVE-9277) Hybrid Hybrid Grace Hash Join
Date Wed, 07 Jan 2015 18:32:34 GMT


Mostafa Mokhtar updated HIVE-9277:
    Assignee:     (was: Mostafa Mokhtar)

> Hybrid Hybrid Grace Hash Join
> -----------------------------
>                 Key: HIVE-9277
>                 URL:
>             Project: Hive
>          Issue Type: New Feature
>          Components: Physical Optimizer
>            Reporter: Wei Zheng
>              Labels: join
> 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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