Bazaar traffic during commit

[Óscar Fuentes]

Eli Zaretskii <eliz at gnu.org> writes:

>> > I just committed 2 files whose combined size is 32KB from a bound
>> > branch to the Emacs repository, and Bazaar showed that it moved
>> > 4.5MB through the wire (we are still using SFTP, so I have nothing
>> > better to do than watch the bytes move ;-).
>> >
>> > Is this expected?  What are those megabytes?
>> 
>> As explained here on the past, while aggregating your commits a
>> threshold was surpassed and bzr repacked some part of the remote
>> repository.
>
> Why would repacking a _remote_ repository cause traffic from the
> client to the server?  Isn't it the server who does the repacking in
> this case?

The sftp server is dumb. It knows how to move files around, but not
about moving chunks of bytes from one file to another. For this, the
client needs to download the bytes from the original file and upload to
put them on the target file. This is the case too when the original and
the target files are the same.

Apart from this, repacking requires de-compressing and re-compressing
data. That means that even if the sftp server could be commanded to move
chunks of bytes around, it wouldn't be enough, as the data must be
processed before moving it elsewhere.