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https://issues.apache.org/jira/browse/PHOENIX-4148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16151241#comment-16151241
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James Taylor commented on PHOENIX-4148:
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Yes, that sounds right. The MemoryManager is really just tracking how much
memory is used, not doing the actual allocation. So you'd essentially reserve
each 1MB chunk and then allocate it yourself (or allocate lots of small chunks
that add up to 1MB) - it doesn't have to match up exactly with what you've
reserved in the MemoryManager.
> 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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