Re: The most efficient way to test if repositories share the same objects

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 22, 2018, 21:44 UTC
Message-ID: <xmqqa7uzlr8x.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <906555df-e906-775a-0255-fbc71f7138f6@linuxfoundation.org>

Konstantin Ryabitsev <konstantin@linuxfoundation.org> writes:

Show 12 quoted lines

> $ time git rev-list --max-parents=0 HEAD
> a101ad945113be3d7f283a181810d76897f0a0d6
> cd26f1bd6bf3c73cc5afe848677b430ab342a909
> be0e5c097fc206b863ce9fe6b3cfd6974b0110f4
> 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
>
> real    0m6.311s
> user    0m6.153s
> sys     0m0.110s
>
> If I try to do this for each of the 7700 heads, this will take roughly
> 12 hours.

Wouldn't it be more efficient to avoid doing so one-by-one? That is, wouldn't

	rev-list --max-parents=0 --all

be a bit faster than

	for-each-ref |
	while read object type refname
	do
		rev-list --max-parents=0 $refname
	done

I wonder?