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From "Thomas Mueller (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-2857) Support sequential (non-random) node ids
Date Thu, 06 Jan 2011 08:32:49 GMT

    [ https://issues.apache.org/jira/browse/JCR-2857?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12978215#action_12978215
] 

Thomas Mueller commented on JCR-2857:
-------------------------------------

One solution to ensure uniqueness is to use a unique repository-wide id as the base or most
significant bits of the node id. I think it's better to not change this base id on each startup.
With the patch, it's already possible to emulate this (set the system property jackrabbit.sequentialNodeId
to <unique-repository-wide-id-msb>/<unique-repository-wide-id-lsb>, for example
"14f0acef/0"). The patch let's you 'test drive' sequential node ids, and includes the necessary
refactoring of the node id generation (the NodeIdFactory mechanism), but the patch doesn't
generate a random base id automatically yet. I will change that: when the jackrabbit.sequentialNodeId
is set to "true", use a random base id instead of 0/0.

I agree in the long term, it makes sense to let the persistence layer generate unique node
ids. In my J3 prototype this is already implemented. For the current Jackrabbit code, it would
mean a lot of changes because each component would need to have a reference to the persistence
layer, or let the persistence layer generate node id factories. But I don't think Jackrabbit
would be much faster if the persistence layer generates the node ids - just it would make
sense on an architecture level in the long term. But if we anyway want to replace the current
Jackrabbit code with new code it doesn't make sense to change that now.


> Support sequential (non-random) node ids
> ----------------------------------------
>
>                 Key: JCR-2857
>                 URL: https://issues.apache.org/jira/browse/JCR-2857
>             Project: Jackrabbit Content Repository
>          Issue Type: Improvement
>          Components: jackrabbit-core
>            Reporter: Thomas Mueller
>            Assignee: Thomas Mueller
>         Attachments: jcr-2857.patch
>
>
> Currently, node ids are generated using a (cryptographically secure pseudo-) random number
generator. This has a many advantages (easy to implement, easy to merge nodes from multiple
repositories or cluster nodes), but is a performance bottleneck for large repositories.
> In addition to generating random node ids, Jackrabbit should support generating sequential
node ids.

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