Re: does a successful 'git gc' imply 'git fsck'

On Sun, Dec 2, 2012 at 9:58 AM, Shawn Pearce [off-list ref] wrote:

On Sat, Dec 1, 2012 at 6:31 PM, Sitaram Chamarty [off-list ref] wrote:

quoted

Background: I have a situation where I have to fix up a few hundred
repos in terms of 'git gc' (the auto gc seems to have failed in many
cases; they have far more than 6700 loose objects).  I also found some
corrupted objects in some cases that prevent the gc from completing.

I am running "git gc" followed by "git fsck".  The majority of the
repos I have worked through so far appear to be fine, but in the
larger repos (upwards of 2-3 GB) the git fsck is taking almost 5 times
longer than the 'gc'.

If I could assume that a successful 'git gc' means an fsck is not
needed, I'd save a lot of time.  Hence my question.

Not really. For example fsck verifies that every blob when
decompressed and fully inflated matches its SHA-1. gc only checks

OK that makes sense.  After I posted I happened to check using strace
and kinda guessed this from what I saw, but it's nice to have
confirmation.

connectivity of the commit and tree graph by making sure every object
was accounted for. But when creating the output pack it only verifies
a CRC-32 was correct when copying the bits from the source to the
destination, it does not verify that the data decompresses and matches
the SHA-1 it should match.

So it depends on what level of check you need to feel safe.

Yup; thanks.

All the repos my internal client manages are mirrored in multiple
places, and they set (or were at least told to set, heh!)
receive.fsckObjects so the lesser check is fine in most cases.

-- 
Sitaram