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From "James Taylor (JIRA)" <>
Subject [jira] [Commented] (PHOENIX-4148) COUNT(DISTINCT(...)) should have a memory size limit
Date Fri, 01 Sep 2017 22:26:00 GMT


James Taylor commented on PHOENIX-4148:

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:
>             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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