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

On Fri, 22 Sep 2017 17:32:00 -0400
Jeff Hostetler [off-list ref] 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?

quoted

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.