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https://issues.apache.org/jira/browse/DERBY-5416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13913354#comment-13913354
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ASF subversion and git services commented on DERBY-5416:
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Commit 1572203 from [email protected] in branch 'code/branches/10.10'
[ https://svn.apache.org/r1572203 ]
DERBY-5416: SYSCS_COMPRESS_TABLE causes an OutOfMemoryError when the
heap is full at call time and then gets mostly garbage collected later
on.
backporting change #1550103 from trunk to 10.10.
Improve the accuracy of the code that estimates the memory requirement
of the sort buffer. When it detects that the current memory usage is
lower than the initial memory usage, it now records the current usage
and uses that value instead of the initial memory usage in future
calculations.
This compensates to some degree, but not fully, for the skew in the
estimates due to garbage collection happening after the initial memory
usage. The memory requirement will not be as badly underestimated, and
the likelihood of OutOfMemoryErrors is reduced.
There is no regression test case for this bug, since the only
reliable, reproducible test case that we currently have, needs too
much time, disk space and memory to be included in the regression test
suite.
> SYSCS_COMPRESS_TABLE causes an OutOfMemoryError when the heap is full at call
> time and then gets mostly garbage collected later on
> ----------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-5416
> URL: https://issues.apache.org/jira/browse/DERBY-5416
> Project: Derby
> Issue Type: Bug
> Components: Store
> Affects Versions: 10.6.2.1, 10.7.1.1, 10.8.1.2
> Reporter: Ramin Baradari
> Assignee: Mike Matrigali
> Priority: Critical
> Labels: derby_triage10_9
> Fix For: 10.11.0.0
>
> Attachments: compress_test_5416.patch, d5416-1a.diff, lowmem-test.diff
>
>
> When compressing a table with an index that is larger than the maximum heap
> size and therefore cannot be hold in memory as a whole an OutOfMemoryError
> can occur.
> For this to happen the heap usage must be close to the maximum heap size at
> the start of the index recreation and then while the entries are sorted a
> garbage collection run must clean out most of the heap. This can happen
> because a concurrent process releases a huge chunk of memory or just because
> the buffer of a previous table compression has not yet been garbage
> collected.
> The internally used heuristics to guess when more memory can be used for the
> merge inserter estimates that more memory is available and then the sort
> buffer gets doubled. The buffer size gets doubled until the heap usage is
> back to the level when the merge inserter was first initialized or when the
> OOM occurs.
> The problem lies in MergeInsert.insert(...). The check if the buffer can be
> doubled contains the expression "estimatedMemoryUsed < 0" where
> estimatedMemoryUsed is the difference in current heap usage and heap usage at
> initialization. Unfortunately, in the aforementioned scenario this will be
> true until the heap usage will reach close to maximum heap size before
> doubling the buffer size will be stopped.
> I've tested it with 10.6.2.1, 10.7.1.1 and 10.8.1.2 but the actual bug most
> likely exists in prior versions too.
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