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Re: svn commit: r1546619 - /subversion/branches/fsfs-ucsnorm/BRANCH-README

From: Branko Čibej <brane_at_wandisco.com>
Date: Fri, 29 Nov 2013 21:09:11 +0100

On 29.11.2013 20:42, Ivan Zhakov wrote:
> On 29 November 2013 22:22, <brane_at_apache.org> wrote:
>> Author: brane
>> Date: Fri Nov 29 18:22:00 2013
>> New Revision: 1546619
>>
>> URL: http://svn.apache.org/r1546619
>> Log:
>> * branches/fsfs-ucsnorm/BRANCH-README: New file.
>>
>> Added:
>> subversion/branches/fsfs-ucsnorm/BRANCH-README (with props)
>>
>> Added: subversion/branches/fsfs-ucsnorm/BRANCH-README
>> URL: http://svn.apache.org/viewvc/subversion/branches/fsfs-ucsnorm/BRANCH-README?rev=1546619&view=auto
>> ==============================================================================
>> --- subversion/branches/fsfs-ucsnorm/BRANCH-README (added)
>> +++ subversion/branches/fsfs-ucsnorm/BRANCH-README [UTF-8] Fri Nov 29 18:22:00 2013
>> @@ -0,0 +1,66 @@
>> +The purpose of this [fsfs-ucsnorm] branch is to implement two optional
>> +checks related to Unicode normalisation to FSFS.
>> +
>> +
>> +Option: Prevent name collisions
>> +===============================
>> +
>> +If this option is enabled, FSFS will reject operations that would
>> +create two different representations of the same name in the same
>> +directory. This will prevent situations where a user could see more
>> +than one form of the name in a directory listing:
> Nice feature, but why in FS layer? May be it's better to implement
> this feature on svn_repos layer?

It's not, for at least two reasons:

  * Users of the FS API must have the same constraints as repository
    clients, otherwise the whole thing falls on its face.
  * The repos layer cannot implement this optimally; at a rough guess,
    it would have to double the number of lookups performed:
      o The node cache in an FSFS implementation detail, and this option
        will affect how cache keys are generated.
      o Likewise for actual lookups into the on-disk representation.

-- Brane

-- 
Branko Čibej | Director of Subversion
WANdisco // Non-Stop Data
e. brane_at_wandisco.com
Received on 2013-11-29 21:10:15 CET

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