[jira] [Commented] (ASTERIXDB-1556) Hash Table used by External hash group-by doesn't conform to the budget.

["Yingyi Bu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ASTERIXDB-1556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15474894#comment-15474894 ] 

Yingyi Bu commented on ASTERIXDB-1556:
--------------------------------------

[~wangsaeu], 

GC can be done in a simpler way (to me), using two steps:
step 1. "blindly" compact content frames -- doing chunk byte copies.  Think of frames as 4 byte continuous units.  A byte region doesn't contain a 0XFFFF unit is a chunk.
step 2. rebuilds the header frame from scratch.

This at least simplifies step 1.  Also, I don't think step 1 or step 2 require additional memory (i.e., frames).

> 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
>            Priority: Critical
>              Labels: soon
>         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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