about the delta technique used in Bazaar

[Martin Pool]

On 3 July 2013 05:03, Bo Chen <chen at chenirvine.org> wrote:

> Thanks. Martin.
>
> I am also curious on some more specific aspects:
> 1) in this group, it only includes different versions of the same file, or
> can include versions from other files?
>

I think it can include other files.


> 2) how to choose the base for delta?
>

This isn't really a system where there is a delta base.


> I don't know python, and cannot read the code you provided.
>
> Thanks.
>
> Bo
>
>
>
> On Tue, Jul 2, 2013 at 2:07 AM, Martin Pool <mbp at sourcefrog.net> wrote:
>
>> bzr's compression is in the 'groupcompress<http://bazaar.launchpad.net/~bzr-pqm/bzr/bzr.dev/view/head:/bzrlib/groupcompress.py>'
>> module. Briefly, this stores a set of related file versions together, and
>> then does gzip entropy compression across the whole set of them. This gives
>> a good compression, including compression across files, while bounding the
>> amount of data that has to be read to unpack any single versions. Files are
>> recompressed over time in to larger groups (up to a certain ceiling) so
>> that older versions get more compression and slightly longer access time.
>>
>>
>> On 2 July 2013 15:08, Bo Chen <chen at chenirvine.org> wrote:
>>
>>> version control systems usually use delta techniques to optimize the
>>> storage of the repository. Can anyone tell me what delta technique
>>> Bazaar uses? Reverse delta? forward delta? others?
>>>
>>> Thanks.
>>>
>>> Bo
>>>
>>>
>>
>>
>> --
>> Martin
>>
>
>


-- 
Martin
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