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From "Damien Carol (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-9277) Hybrid Hybrid Grace Hash Join
Date Fri, 20 Feb 2015 12:44:12 GMT

     [ https://issues.apache.org/jira/browse/HIVE-9277?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Damien Carol updated HIVE-9277:
-------------------------------
    Description: 
We are proposing an enhanced hash join algorithm called _“hybrid hybrid grace hash join”_.

We can benefit from this feature as illustrated below:
* The query will not fail even if the estimated memory requirement is slightly wrong
* Expensive garbage collection overhead can be avoided when hash table grows
* 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.

  was:
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.


> 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:
> * The query will not fail even if the estimated memory requirement is slightly wrong
> * Expensive garbage collection overhead can be avoided when hash table grows
> * 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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