[ZODB-Dev] [Plone-Users] question about using repozo and blob storage

[Tres Seaver]

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Ralf Hemmecke wrote:
> Tres Seaver <tseaver <at> palladion.com> writes:
> 
>> Sharing the blobs using a DVCS pull sounds like an interesting approach.
>>  One flaw with your outlined implementation is that ZODB blob files are
>> *never* updated:  rather, if a ZODB object updates the blob object, it
>> creates a new blob file and stores its ID.  Old blob files are cleaned
>> up during a pack.
> 
> Interesting. You know what git does? If one adds a file X (actually git deals
> with contents not files) to the repository, git computes a hash value (sha1) and
> uses that value as the name for the file. It's stored under the .git directory.
> Some update of bookkeeping data and that's it.
> If the contents of the file X changes, and it is committed to the git
> repository, git computes a sha1 and stores the new content under that new sha1
> name + updating of the bookkeeping. The old file is not deleted. Git does not
> even bother to compress anything. That would be done by an additional "git gc".
> In contrast to most other SCMs git can be considered as a database. That git is
> mostly recognized as a version control system, is only half of the story. The
> underlying storage system is what make git so interesting.
> 
> I have no good knowledge of zodb and you are certainly doing great with it, but
> my concern is with the blobs (which as I hopefully understand correctly are to
> be stored outside of Plone's Data.fs).
> Storing versions of files into a DVCS is like freeing the zodb (for blobs) from
> doing its own versioning.
> 
> Actually, I think conceptually git and the zodb are quite similar. One
> transaction is nothing else than a commit in the SCM sense.
> 
>> If you want to experiment with the idea anyway, then writing a "wrapper"
>> storage is probably the way to go:  DemoStorage is one such beast, as is
>> the BlobStorage itself.
> 
> I'm sorry, I cannot do this. I've simply no time for opening up another area of
> development for me.

I understand that completely:  I'm there myself. ;)


Tres.
- --
===================================================================
Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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