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https://issues.apache.org/jira/browse/DERBY-5416?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ramin Baradari updated DERBY-5416:
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Attachment: compress_test_5416.patch
> 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
> Priority: Critical
> Attachments: compress_test_5416.patch
>
>
> 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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