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

On 9/22/2017 6:58 PM, Jonathan Tan wrote:

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

quoted

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.)

quoted

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?

I just meant could we add a bit to "struct object_info" to indicate
that the object was found in a .promisor packfile ?  This could
be set in sha1_object_info_extended().

Then the is_promised() calls in fsck and gc would just test that bit.

Given that that bit will be set on promisOR objects (and we won't
have object_info for missing objects), you may need to adjust the
iterator in the fsck/gc code slightly.

This is a bit of a handwave, but could something like that eliminate
the need to build this oidset?

quoted

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.