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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-4148) COUNT(DISTINCT(...)) should have a memory size limit
Date Sat, 02 Sep 2017 01:49:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-4148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16151366#comment-16151366
] 

Lars Hofhansl commented on PHOENIX-4148:
----------------------------------------

Hmm... How do I find the tenant id all the way down in DistinctValueWithCountServerAggregator?

Also it seems we're double allocating a bit (unless I am missing something):
* In GroupedAggregateRegionObserver groupByCache we group by the key
* DistinctValueWithCountServerAggregator we group again to get the count



> COUNT(DISTINCT(...)) should have a memory size limit
> ----------------------------------------------------
>
>                 Key: PHOENIX-4148
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4148
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>
> I just managed to kill (hang) a region server by issuing a COUNT(DISTINCT(...)) query
over a column with very high cardinality (20m in this case).
> This is perhaps not a useful thing to do, but Phoenix should nonetheless not allow to
have a server fail because of a query.
> [~jamestaylor], I see there GlobalMemoryManager, but I do not quite see how I'd get a
reference to one, once needs a tenant id, etc.



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