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Re: Why we have NULL txn_id for delta representation?

From: Kamesh Jayachandran <kamesh_at_collab.net>
Date: 2006-03-09 13:22:57 CET

Max,

Fine. Will it worth a mention in the subversion/libsvn_fs_base/structure
doc?

My current understanding of mutablity is that history(past) should not
be muted, not the internal representation of it, i.e representation
could change from 'fulltext' to 'delta' and viceversa as long as view of
the consumers of the representation is same before and after this change.

I am yet to see how/where the cloning happens.
I guessed by reading the subversion/libsvn_fs_base/fs-history doc that
on each change of the path all the path components are cloned and
corresponding changes are done to a clone, wondered that there should be
no such cloning in 'representations' and 'strings' tables as the
youngest is always fulltext.

Thanks.
With regards
Kamesh Jayachandran

Max Bowsher wrote:
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> Kamesh Jayachandran wrote:
>
>> Hi,
>> I could see all 'delta' representations having TXN as 0. I could see the
>> code of subversion/libsvn_fs_base/reps-strings.c@18787:line 1544 causing
>> this behaviour.
>>
>> Can someone clarify.
>>
>> P.S I could see the mention of Representation's TXN acting as a kind of
>> mutablity flag.
>>
>
> Yes, that is correct.
>
> delta reps have no txn_id because they are never considered mutable.
>
>
>> I think we clone only the 'nodes' entries for the path
>> getting changed not the representations, as we put the youngest as
>> 'fulltext' so why we need to clone the corresponding representations
>> rather we can create new representations.
>>
>
> I totally don't understand that sentence.
>
> Max.
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Received on Thu Mar 9 13:57:07 2006

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