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From "Taewoo Kim (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ASTERIXDB-1556) Hash Table used by External hash group-by doesn't conform to the budget.
Date Mon, 08 Aug 2016 03:32:20 GMT

    [ https://issues.apache.org/jira/browse/ASTERIXDB-1556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15411223#comment-15411223
] 

Taewoo Kim commented on ASTERIXDB-1556:
---------------------------------------

The hash slots for the hash values in the corresponding the partition are re-initialized (capacity
remains the same and # of used count becomes 0 so that future insertions can use the slot
again). The only time the space is not used again is when we double the capacity of the hash
slot.

> Hash Table used by External hash group-by doesn't conform to the budget.
> ------------------------------------------------------------------------
>
>                 Key: ASTERIXDB-1556
>                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-1556
>             Project: Apache AsterixDB
>          Issue Type: Bug
>            Reporter: Taewoo Kim
>            Assignee: Taewoo Kim
>         Attachments: 2wayjoin.pdf, 2wayjoin.rtf, 2wayjoinplan.rtf, 3wayjoin.pdf, 3wayjoin.rtf,
3wayjoinplan.rtf
>
>
> When we enable prefix-based fuzzy-join and apply the multi-way fuzzy-join ( > 2),
the system generates an out-of-memory exception. 
> Since a fuzzy-join is created using 30-40 lines of AQL codes and this AQL is translated
into massive number of operators (more than 200 operators in the plan for a 3-way fuzzy join),
it could generate out-of-memory exception.
> /// Update: as the discussion goes, we found that hash table in the external hash group
by doesn't conform to the frame limit. So, an out of memory exception happens during the execution
of an external hash group by operator.



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