Re: git receive-pack deletes refs one at a time?

[Jeff King <peff@peff.net>]

On Thu, Jun 13, 2019 at 11:33:40AM -0600, Nasser Grainawi wrote:

> I have a situation where I need to delete 100k+ refs on 15+ separate
> hosts/disks. This setup is using Gerrit replication, so I can trigger
> it all on one host and it will push the deletes to the rest (all
> running git-daemon v2.18.0 with receive-pack enabled). All the refs
> being deleted on the receiving ends are packed.
> 
> What I see is the packed-refs file getting locked/updated over and
> over for each ref. I had assumed it would do something more like
> 'update-ref --stdin' and do a bulk removal of refs. Am I seeing the
> correct behavior? If yes, is there a specific reason it works this way
> or is "bulk delete through push" just a feature that hasn't been
> implemented yet?

The underlying ref code is smart enough to coalesce all of the deletions
in a single transaction into a single write of the packed-refs file.

But historically, pushes do not do a single ref transaction because we
would allow the push for one ref to succeed while others failed. Later,
we added an "atomic" mode that does it all in a single transaction.

Try with "git push --atomic", which should be able to do it in a single
write.

-Peff