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From P├ęter <e2qb2a...@prolan-power.hu>
Subject Backward or forward deltas, backend, FSX
Date Thu, 15 Feb 2018 18:47:54 GMT
[I am not a list member]

In the proposed FSX backend,
[ https://subversion.apache.org/docs/release-notes/1.9.html#fsx ]
what type of deltas is planned? Deltas against an older - or newer revision?
[ http://svn.apache.org/repos/asf/subversion/trunk/notes/skip-deltas ]
FSFS-like way, or BDB-like way?

Please explain it, why was that chosen. Why is optimal. Or, if not quite decided/fixed, please
consider carefully.


I know almost nothing (nor want to) about the internals ("fulltext and txdelta caching" etc.),
but:
I would (as everybody :) prefer the variant which uses less space (less cache, maybe only
one - the last revision), and 
at the same time less time for extracting revision, with strong weight to the last (just added)
revision, and the last 
few revisions.

With say, 100000 revisions, when someone checks out the last revision: svn starts (would start,
with the FSX backend) 
with the 30 years old, "fossile" ancient revision? (It would be case with the "FSFS-like way".)
Which has nothing common 
with the recent revisions? And applies (at least) 17 deltas (patches)? Of which many deltas
are very "heavy" (huge 
changings, complete rewritings)?.. I would marvel at that and do not understand the reasons..


Peter





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