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From "Alexander Klimetschek (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (JCR-3534) Add JackrabbitSession.getValueByContentId method
Date Mon, 18 Mar 2013 17:26:16 GMT

    [ https://issues.apache.org/jira/browse/JCR-3534?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13605375#comment-13605375
] 

Alexander Klimetschek commented on JCR-3534:
--------------------------------------------

Yes, a shared data store can be a much more viable option than a full cluster (considering
Jackrabbit 2 here). The whole point is to optimize for large binaries, to avoid sending them
around and to minimize disk space. Switching to a full cluster in the use case we have (as
described by Felix above) is not an option, as the JCR content will be different on the instances
that should share the data store.

I agree that we should consider the long term as well - but I don't know if there are actual
better mechanisms, and I don't know of any being worked on for Oak already.
                
> Add JackrabbitSession.getValueByContentId method
> ------------------------------------------------
>
>                 Key: JCR-3534
>                 URL: https://issues.apache.org/jira/browse/JCR-3534
>             Project: Jackrabbit Content Repository
>          Issue Type: New Feature
>          Components: jackrabbit-api, jackrabbit-core
>    Affects Versions: 2.6
>            Reporter: Felix Meschberger
>         Attachments: JCR-3534.patch
>
>
> we have a couple of use cases, where we would like to leverage the global data store
to prevent sending around and copying around large binary data unnecessarily: We have two
separate Jackrabbit instances configured to use the same DataStore (for the sake of this discussion
assume we have the problems of concurrent access and garbage collection under control). When
sending content from one instance to the other instance we don't want to send potentially
large binary data (e.g. video files) if not needed.
> The idea is for the sender to just send the content identity from JackrabbitValue.getContentIdentity().
The receiver would then check whether the such content already exists and would reuse if so:
> String ci = contentIdentity_from_sender;
> try {
>     Value v = session.getValueByContentIdentity(ci);
>     Property p = targetNode.setProperty(propName, v);
> } catch (ItemNotFoundException ie) {
>     // unknown or invalid content Identity
> } catch (RepositoryException re) {
>     // some other exception
> }
> Thus the proposed JackrabbitSession.getValueByContentIdentity(String) method would allow
for round tripping the JackrabbitValue.getContentIdentity() preventing superfluous binary
data copying and moving. 
> See also the dev@ thread http://jackrabbit.markmail.org/thread/gedk5jsrp6offkhi

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