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https://issues.apache.org/jira/browse/JCR-926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12526722
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Thomas Mueller commented on JCR-926:
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Compatibility: the plan is to make this feature fully backward compatible. When
the system property 'org.jackrabbit.useDataStore' is enabled, and when
FileDataStore is configured in repository.xml, old repositories can still be
used. Only new binary objects are stored in the data store, and only when this
is configured in repository.xml.
Migration to data store: binary data that is currently in the blob store (or in
the persistence manager) can be moved to the data store by cloning a workspace,
or export / import.
Migration away from the data store: currently, you need to export the data with
the data store enabled / configured, and then import into a new repository
without data store.
> Global data store for binaries
> ------------------------------
>
> Key: JCR-926
> URL: https://issues.apache.org/jira/browse/JCR-926
> Project: Jackrabbit
> Issue Type: New Feature
> Components: core
> Reporter: Jukka Zitting
> Attachments: dataStore.patch, DataStore.patch, DataStore2.patch,
> dataStore3.patch, dataStore4.zip, dataStore5-garbageCollector.patch,
> internalValue.patch, ReadWhileSaveTest.patch
>
>
> There are three main problems with the way Jackrabbit currently handles large
> binary values:
> 1) Persisting a large binary value blocks access to the persistence layer for
> extended amounts of time (see JCR-314)
> 2) At least two copies of binary streams are made when saving them through
> the JCR API: one in the transient space, and one when persisting the value
> 3) Versioining and copy operations on nodes or subtrees that contain large
> binary values can quickly end up consuming excessive amounts of storage space.
> To solve these issues (and to get other nice benefits), I propose that we
> implement a global "data store" concept in the repository. A data store is an
> append-only set of binary values that uses short identifiers to identify and
> access the stored binary values. The data store would trivially fit the
> requirements of transient space and transaction handling due to the
> append-only nature. An explicit mark-and-sweep garbage collection process
> could be added to avoid concerns about storing garbage values.
> See the recent NGP value record discussion, especially [1], for more
> background on this idea.
> [1]
> http://mail-archives.apache.org/mod_mbox/jackrabbit-dev/200705.mbox/[EMAIL
> PROTECTED]
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