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From P├ęter <>
Subject Re: Backward or forward deltas, backend, FSX
Date Fri, 16 Feb 2018 22:52:56 GMT

An additional minor question: when making "big" (skip-) deltas from smaller deltas: does not
this mean that for many 
changes (rev[N] -> rev[N+1]) this change will be included (redundantly) in many deltas?
So, we gain some speed - but at 
the cost of size. It is against the "store every piece [fragment?] only once" principle.
(And it is not fully clear for me why would be [lot?] quicker playing the same A + B changes
as 1 delta, than playing as 
2 deltas? Aside from the [rare] cases when change B does some "opposite" of A.)

Daniel Shahaf:
> FSFS and FSX are designed around the assumption that the storage backing
> older revisions is immutable.

Older revisions (older than the very last revision) can be kept read-only in both cases, I
think. (What am I missing?)

> max-linear-deltification (see fsfs.conf) is 16, meaning that no fulltext
> will require 17 delta applications to produce.

(Okay, the number of applicated deltas was reduced, but not the amount of changes. The whole
(or half?) of the complete 
"life" of some file may be re-played, just to yield the current state. Analogue: for an animal
(for example, frog): 
"let's start with this single cell; then apply changes A, then.......................... here
is the frog".)


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