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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-646) In-memory backend storage support
Date Mon, 09 Feb 2009 13:35:00 GMT

    [ https://issues.apache.org/jira/browse/DERBY-646?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12671849#action_12671849
] 

Kristian Waagan commented on DERBY-646:
---------------------------------------

I had a quick look at this again, looking at how an in-memory backend could be wired into
Derby.
>From what I can see, the easiest way is to add a single entry to BaseMonitor (and the
new constant for the subSubProtocol):
  storageFactories.put( PersistentService.VFMEM, "org.apache.derby.impl.io.VFMemoryStorageFactory");

If VFMemoryStorageFactory (or whatever the class will be called) behaves in the expected way,
everything should "just work". The solution won't be optimal. The primary goal is to offer
a configuration that doesn't leave any trace in the form of files and directories. Performance
may be somewhat better, but the memory usage will be high.  Not only will all the data be
stored in memory, parts of it will be stored in multiple copies in memory.
Note that even though the configuration will implement  PersistentService, data won't be persisted
beyond the life-time of the JVM running Derby. If this causes any problems with rest of the
code, remains to be seen.

A new service could be implemented as well, but I think this will require a lot more effort
(feel free to comment on this if you have more information).

I'll play some more with the idea and post my findings.

> 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
>         Environment: All
>            Reporter: Stephen Fitch
>         Attachments: derby-646-1a-raw-compiles.diff, derby-646-1a-raw-compiles.stat,
svn.diff
>
>
> To allow creation and modification of databases in-memory without requiring disk access
or space to store the database.

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