Hi Jonathan, On Wed, 15 May 2019, Jonathan Tan wrote: > > > To resolve this, prefetch all missing REF_DELTA bases before attempting > > > to resolve them. This both ensures that all bases are attempted to be > > > fetched, and ensures that we make only one request per index-pack > > > invocation, and not one request per missing object. > > > > Hmm. I wonder whether this can lead to *really* undesirable behavior, e.g. > > with deep delta chains. The client would possibly have to fetch the > > REF_DELTA object, but that would also be delivered in a thin pack with > > *another* REF_DELTA object, and the same over and over again, with plenty > > of round trips that kill performance really well. > > When the client fetches the REF_DELTA base, it won't be a REF_DELTA > object itself because Git makes these fetches without any "have" lines, > so the server doesn't know anything to delta against. Admittedly, this > is just due how to we implemented it - if later we find a way to > optimize the lazy fetches by adding "have", then we'll have to revisit > this. Ah! I *think* I understand this better now. Thank you. > Quoting from the commit message: > > > > (When fetching REF_DELTA bases, it is unlikely that > > > those are REF_DELTA themselves, because we do not send "have" when > > > making such fetches.) > > I tried to address this point with this sentence in the commit message. > If you think that this should be addressed more clearly in the commit > message, let me know if you have any suggestions. I totally read over this part of the commit message, apparently. My bad. Sorry for the noise! Dscho
