Re: RFC: Design and code of partial clones (now, missing commits and trees OK) (part 3)

From: Jonathan Tan <jonathantanmy@google.com>
Date: Sep 22, 2017, 22:58 UTC
Message-ID: <20170922155802.ab79717818578a23cc31f6fe@google.com>
In-Reply-To: <7977bab0-09c3-0e43-4d6f-f2bf87a3fd9e@jeffhostetler.com>

On Fri, 22 Sep 2017 17:32:00 -0400 Jeff Hostetler <git@jeffhostetler.com> wrote:

> I guess I'm afraid that the first call to is_promised() is going
> cause a very long pause as it loads up a very large hash of objects.

Yes, the first call will cause a long pause. (I think fsck and gc can tolerate this, but a better solution is appreciated.)

> Perhaps you could augment the OID lookup to remember where the object
> was found (essentially a .promisor bit set).  Then you wouldn't need
> to touch them all.

Sorry - I don't understand this. Are you saying that missing promisor objects should go into the global object hashtable, so that we can set a flag on them?

> > The oidset will deduplicate OIDs.
> 
> Right, but you still have an entry for each object.  For a repo the
> size of Windows, you may have 25M+ objects your copy of the ODB.

We have entries only for the "frontier" objects (the objects directly referenced by any promisor object). For the Windows repo, for example, I foresee that many of the blobs, trees, and commits will be "hiding" behind objects that the repository user did not download into their repo.