On 14.01.2022 21:29, Julian Foad wrote:
multi-wc-format branch [...] anything I'm missing?
As soon as I stepped away I could see more clearly: Basically
'multi-wc-format' is just providing an API up to the client layer for
enumerating WC format variants. The same logical functionality could be
implemented for a particular feature (e.g. pristines-on-demand) by
looking directly at some other on-disk representation change to
distinguish variants within one format number; this branch just
formalizes and generalizes it. It doesn't make more or better
compatibility than could be done ad-hoc; it doesn't magically make old
clients be able to work with newer formats/variants than they know about.
I expect you mean, "that they *don't* know about."
So, in the context of whether it makes sense to adopt the
'multi-wc-format' branch versus implementing the WC pristines code to
work ad-hoc with two on-disk variants, it comes down to:
- cost of adopting (reviewing etc.) the 'multi-wc-format' vs.
implementing something ad-hoc for pristines;
- potential future benefit from re-using 'multi-wc-format' for other changes.
My original motivation to starting multi-wc-format was to implement
compressed pristines and in-wc-db pristines for small (for some
definition of) files. There may be a branch for that (I don't recall)
and some infrastructure work in spillbufs that could be reused.
Cost of adopting 'multi-wc-format' looks likely to be lower. It is
mostly boiler-plate changes and simple code, and is fairly small
compared with the overall task:
'pristines-on-demand' diff size: +2700 -1000 lines roughly
'multi-wc-format' diff size: +1000 -200 lines roughly
From this perspective, it looks best to adopt 'multi-wc-format' unless
we find some show-stopper problem with it.
That would be my recommendation, too, if only to have just one specific
way to add feature support to the WC without requiring a WC upgrade
every time. We've mostly tied WC features to the format version, it
would seem natural to keep that correlation.
p.s. I forgot to say, in updating 'multi-wc-format' I found a few small
problems, two of which I fixed; one remains, causing the 'upgrade' tests
to fail, which is due to '#ifdef SVN_TEST_MULTI_WC_FORMAT' in
'wc-metadata.sql', which doesn't get processed as a directive and needs
to be handled some other way.
I know about that one, yes. I essentially ran out of oomph before fixing
it; it might be as simple as a adding a small enhancement to the SQL
statement processing scripts.
-- Brane
