[tahoe-lafs-trac-stream] [tahoe-lafs] #1209: repair of mutable files/directories should not increment the sequence number

[tahoe-lafs]

#1209: repair of mutable files/directories should not increment the sequence
number
-------------------------+-------------------------------------------------
     Reporter:  gdt      |      Owner:  davidsarah
         Type:  defect   |     Status:  assigned
     Priority:  major    |  Milestone:  soon
    Component:  code-    |    Version:  1.8.0
  mutable                |   Keywords:  repair mutable preservation space-
   Resolution:           |  efficiency
Launchpad Bug:           |
-------------------------+-------------------------------------------------

Comment (by davidsarah):

 Brian replied:
 > On 3/29/12 12:01 PM, Greg Troxel wrote:
 > >
 > > More than that - if we have 1 share of M and all shares of N, for N >
 > > M, then we really just want to purge (or ignore?) the M share, and not
 > > molest the N shares.
 >
 > Ah, good point. We really only need a new version if there are multiple
 competing versions with the same sequence number, and if that sequence
 number is the highest seen. Repair is tricky in that case anyways, since
 at the Tahoe level we can't do an automatic merge, so we're certainly
 losing information (if it's just a directory modification, then the
 directory.py code can re-apply the modification, so that one case might be
 safe).
 >
 > Hm, {{{ServerMap.needs_merge()}}} is pretty close already, but it only
 looks at recoverable versions (it tells you that an update will lose
 information that would have been recoverable if you'd read the individual
 versions first.. there are alternate cases where it doesn't matter because
 the other versions weren't recoverable anyways).
 >
 > We should add a method to {{{ServerMap}}} that tells us whether a new
 version is needed or not.
 >
 > > The above test is how the pubgrid feels to me, or used to.
 >
 > Yup, that test looks right.

-- 
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1209#comment:14>
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