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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-646) In-memory backend storage support
Date Wed, 25 Mar 2009 14:44:51 GMT

    [ https://issues.apache.org/jira/browse/DERBY-646?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12689121#action_12689121

Kristian Waagan commented on DERBY-646:

Thanks for testing the new feature, Knut Magne :)
I'm currently working on a patch, where I'm considering using java.io.File. That should take
care of any other OS that has a different style for paths as well.
Feel free to log a bug in Jira. If you don't, I will tomorrow.

Regarding memory footprint, you have to balance the memory overhead against performance. Setting
the page cache to the minimum size will degrade performance in many configurations.
The worst case I saw in my simple testing, was a drop from 28361 (pageCacheSize=1000) tps
to 4059 (pageCacheSize=40) tps. This was a single record update test using a page size of
32 K.

I'm not quite sure how you would go about discarding the log records, but you do need the
UNDO log records to support transactions. Doing something in this area should be possible.
I don't know the log system well enough to say something more, but maybe someone else does?

> In-memory backend storage support
> ---------------------------------
>                 Key: DERBY-646
>                 URL: https://issues.apache.org/jira/browse/DERBY-646
>             Project: Derby
>          Issue Type: New Feature
>          Components: Store
>    Affects Versions:
>         Environment: All
>            Reporter: Stephen Fitch
>            Assignee: Kristian Waagan
>         Attachments: derby-646-1a-raw-compiles.diff, derby-646-1a-raw-compiles.stat,
derby-646-20090222.diff, derby-646-20090222.stat, derby-646-2a-vfmem_first_rev.diff, derby-646-2a-vfmem_first_rev.stat,
derby-646-2b-vfmem_first_rev.diff, derby-646-3a-jmx_experiment.diff, derby-646-performance_comparison_1a.txt,
> To allow creation and modification of databases in-memory without requiring disk access
or space to store the database.

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