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From "Jukka Zitting (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (JCR-3534) Add JackrabbitSession.getValueByContentId method
Date Mon, 18 Mar 2013 13:32:16 GMT

    [ https://issues.apache.org/jira/browse/JCR-3534?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13605108#comment-13605108
] 

Jukka Zitting commented on JCR-3534:
------------------------------------

> well, copying lots of 20MB binaries ? instead of lots of 50 character strings ? Do the
math ;-)

I mean the overhead of the extra cluster configuration. Both approaches suggested here achieve
the reduced data transfer, one at the cost of extra API and permissions the other at the cost
of deployment changes. The question here is which one is the better long term alternative.

> The abstraction already leaked with the JackrabbitValue.getContentIdentitiy method

The case for getContentIdentity() is quite different from this use case, and has neither the
security concerns nor any reasonable alternatives that wouldn't require API changes. Unlike
in here, the kinds of use cases enabled with getContentIdentity() are impossible, not just
inconvenient to configure, without the extra API.

                
> 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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