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https://issues.apache.org/jira/browse/JCR-926?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Mueller updated JCR-926:
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Attachment: internalValue.patch
This is a patch to clean up InternalValue.internalValue():
Before replacing the BLOBFileValue class with the new 'Global Data Store'
implementation, I wanted to clean up a few things in InternalValue. The method
InternalValue.internalValue() was called a lot in the Jackrabbit code. It
returns a java.lang.Object which was then cast to the required class. This has
a few disadvantages:
- Unnecessary casts in many places
- Hard to change the internal working of InternalValue, specially replace
BLOBFileValue
- A few times, 'instanceof' was used, making it hard to change BLOBFileValue
- For developers new to the Jackrabbit code (like me), it's not always easy to
understand what is going on in the code
- NodeIndexer used the java.lang.Object directly, assuming the implementation
will always use Boolean, Long, Double, BLOBFileValue and so on objects.
In this patch, I added specific getter methods to InternalValue, like done in
the Value interface. Additionally, there are getPath (for PropertyType.PATH),
getQName (for PropertyType.NAME), and getUUID (for PropertyType.REFERENCE).
I had to make a few assertions, some of them were not 100% clear from the code,
so could you please review them:
- The 'value' of InternalValue is never 'null'.
ValueConstraint was checking for 'null', but as far as I see
it is never really possible to have a 'null' value.
- The type of QName.JCR_FROZENUUID is STRING (Object.toString() was used
before).
- The type of QName.JCR_MIMETYPE is STRING
- The type of QName.JCR_ENCODING is STRING
- Currently, for types PropertyType.BINARY, the object is always
a BLOBFileValue (there was no other constructor for PropertyType.BINARY)
NodeIndexer still has a few unnecessary type casts (addBinaryValue,
addBinaryValue,...) but the methods are protected, and I was afraid to change
them right now. I hope those can be changed soon to avoid a few unnecessary
casts and conversions (Long, Double).
There are no functional changes yet in this patch (as far as I see). But I
think this patch is required, otherwise subsequent changes will be much harder.
I didn't remove InternalValue.internalValue so far, but set it to 'deprecated'.
I hope it can be removed in the near future.
Thomas
> 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, DataStore2.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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