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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4119) Compress on a large table fails with IllegalArgumentException - Illegal Capacity
Date Tue, 31 Mar 2009 12:37:52 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12694084#action_12694084
] 

Knut Anders Hatlen commented on DERBY-4119:
-------------------------------------------

Thanks again for looking at the patch.

It's true that catching the OOME means that we end up with an array that's a lot smaller than
Integer.MAX_VALUE (it doesn't have to be a lot smaller, but with the current value of GROWTH_MULTIPLIER
(2) it will be about half the size). But even if it is smaller than ideal, it will still be
better than the current situation, where it'll crash. And it will also fix problems that may
arise because the amount of available memory has become smaller than it was when we checked
it in MergeInserter.insert() and decided to increase the maximum size (which was the problem
the original check for newArray==null was supposed to fix).

If we had a way to find the exact maximum array size supported by the JVM, I agree that we
should use that limit instead of MAX_VALUE, but it doesn't sound that appealing to guess a
limit that may be suboptimal for JVMs without the limitation, and possibly too large for JVMs
we haven't tested. If it turns out to be a problem, we could improve this further at a later
point by successively trying to allocate a slightly smaller array on OOME until we are able
to allocate it. Hopefully most JVMs will have removed this limitation before it becomes common
for Derby to run into it.

As far as I can see, your assumption is correct that failing to increase the size of the array
will lead to more stages in the sort, and not cause the sort to fail.

> Compress on a large table fails with IllegalArgumentException - Illegal Capacity
> --------------------------------------------------------------------------------
>
>                 Key: DERBY-4119
>                 URL: https://issues.apache.org/jira/browse/DERBY-4119
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.5.1.0
>            Reporter: Kristian Waagan
>            Assignee: Knut Anders Hatlen
>         Attachments: overflow.diff, overflow2.diff, overflow3.diff
>
>
> When compressing a large table, Derby failed with the following exception:
> IllegalArgumentException; Illegal Capacity: -X
> I was able to access the database afterwards, but haven't yet checked if all the data
is still available.
> The compress was started with CALL SYSCS_UTIL.SYSCS_COMPRESS_TABLE('schema', 'table',
1) from ij.
> The data in the table was inserted with 25 concurrent threads. This seems to cause excessive
table growth, as the data inserted should weigh in at around 2 GB. The table size after the
insert is ten times bigger, 20 GB.
> I have been able to generate the table and do a compress earlier, but then I have been
using fewer insert threads.
> I have also been able to successfully compress the table when retrying after the failure
occurred (shut down the database, then booted again and compressed).
> I'm trying to reproduce, and will post more information (like the stack trace) later.
> So far my attempts at reproducing has failed. Normally the data is generated and the
compress is started without shutting down the database. My attempts this far has consisted
of doing compress on the existing database (where the failure was first seen).

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