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https://issues.apache.org/jira/browse/ORC-408?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16643953#comment-16643953
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Sergey Shelukhin edited comment on ORC-408 at 10/9/18 7:02 PM:
---------------------------------------------------------------
According to [~prasanth_j] there is no mechanism that actually reduces the
memory. What version/config is the minimum requirement for that to happen?
Also it would seem that flushing a stripe may not always be possible, and may
require additional memory to do the flush. What we want is the hard limit for
process safety (to avoid GC issues/off heap exhaustion) - as soon as it's hit,
no more non-trivial memory buffers whatsoever can be allocated by any of a set
of writers (until perhaps some memory is freed).
was (Author: sershe):
According to [~prasanth_j] there is no mechanism that actually reduces the
memory. What version/config is the minimum requirement for that to happen?
Also it would seem that flushing a stripe may not always be possible, and may
require additional memory to do the flush. What we want is the hard limit - as
soon as it's hit, no more non-trivial memory buffers whatsoever can be
allocated by any of a set of writers (until perhaps some memory is freed).
> hard limit on memory use by ORC writers
> ---------------------------------------
>
> Key: ORC-408
> URL: https://issues.apache.org/jira/browse/ORC-408
> Project: ORC
> Issue Type: Bug
> Reporter: Sergey Shelukhin
> Priority: Major
>
> Scenario: we want to hard-limit (within the constraints imposed by using
> Java) the memory used by a particular Hive task dedicated to ORC writing, to
> protect other tasks from misbehaving queries. This is similar to how we e.g.
> limit the memory used for hash join - when the hash table goes over the
> limit, the task fails.
> However, we currently cannot even hard-limit this for a single writer, much
> less for several writers combined, when they are writing.
> I wonder if it's possible to add two features to MemoryManager:
> 1) Grouping writers. A tag can be supplied externally (e.g. when creating the
> writer).
> 2) Hard-limiting the memory by tag - if the group exceeds the memory
> allowance, all the corresponding writers should be made to fail on next
> operation, via the callback.
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