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https://issues.apache.org/jira/browse/JCR-3534?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13651755#comment-13651755
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Marcel Reutegger commented on JCR-3534:
---------------------------------------
Summary of an offline discussion with Tommaso, Alex, Jukka, Thomas and Marcel:
- Introduce new interface to Jackrabbit API: ReferenceBinary extending Binary
with getReference method that returns a String
- Add SimpleReferenceBinary class to jcr-commons implementing the above. The
SimpleReferenceBinary methods will throw an exception (IllegalState or
Repository) when accessing Binary interface methods
- SimpleReferenceBinary is created by supplying a String which is
identifier+HMAC
- ReferenceBinary will be created without supplying the HMAC from external. We
will provide a mechanism to get a reference from a blob in store
- Add a new method getReference to DataIdentifier (jackrabbit-core) which
returns a String of the reference
- Create AbstractDataStore from which all DataStore impls extend
- Provide a mechanism in the AbstractDataStore that creates an identifier from
the reference
- The implementations of Binary need to also implement the ReferenceBinary
interface if the binary supports a reference
Client code will then use it like this:
- Create the ReferenceBinary on sender by checking Binary instanceOf
ReferenceBinary
- On receiver side we create a SimpleReferenceBinary from the reference and
create a value using ValueFactory.createValue(Binary) and one passes the
SimpleReferenceBinary
Comments welcome.
> Efficient copying of binaries across repositories with the same data store
> --------------------------------------------------------------------------
>
> 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
> Assignee: Tommaso Teofili
> Attachments: JCR-3534.2.patch, JCR-3534.3.patch, JCR-3534.patch,
> 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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