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Re: Numbers encoding in FSFS log addressing indexes

From: Stefan Fuhrmann <stefan.fuhrmann_at_wandisco.com>
Date: Wed, 25 Jun 2014 17:34:43 +0200

On Wed, Jun 25, 2014 at 5:09 PM, Ivan Zhakov <ivan_at_visualsvn.com> wrote:

> Subversion 1.8 and before in general uses human readable decimal
> format to store numbers in FSFS repositories on disk.

True. However, there are exceptions to that general rule.
The index data uses the same basic encoding as we
already use in txdelta. In both cases, encoding density
is critical I/O performance.

For instance, if you disable deltification in the ruby repo
(but keeping compression active), it explodes to 9.7GB,
a factor of 22.8. From that it should be obvious how
important space efficient encoding is to Subversion.

> Log addressing
> implementation on trunk introduces new encoding for storing numbers in
> indexes. Quoting log addressing indexes format documentation [1]

I'm not even sure there is documentation for our txdelta
on-disk representation. So, FSFS indexes are doing a
better job in that department, ATM.

-- Stefan^2.
Received on 2014-06-25 17:35:11 CEST

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