Re: [PATCH v6 17/19] fsck: Introduce `git fsck --quick`

Hi Junio,

On 2015-06-21 22:35, Junio C Hamano wrote:

Johannes Schindelin [off-list ref] writes:

quoted

On 2015-06-21 19:15, Junio C Hamano wrote:
Michael Haggerty [off-list ref] writes:

quoted

That's brilliant.

Just to make sure I am reading you correctly, you mean the current
overall structure:

[...]

The way I read Michael's mail, he actually meant something different:
if all of the blob-related errors/warnings are switched to "ignore",
simply skip unpacking the blobs.

That is how I read his mail, too.

But because IIRC we do not check anything special with blob other
than we can read it correctly, my description of "overall structure"
stayed at a very high conceptual level.  The unpacking may happen at
a much higher level in the code, i.e. it comes way before this part
of the logic flow:

        if ("is bad_blob ignored?")
		;
	else if (! "is the blob loadable and well-formed?") {

in which case "is bad blobs ignored?" check may have to happen
before we unpack the object.

And I do not suggest introducing yet another BAD_BLOB error class; I
would have guessed that you already have an error class for objects
that are not stored correctly (be it truncated loose object, checksum
mismatch in the packed base object, or corrupt delta in pack).

Sadly, there is no BAD_BLOB class. The reason is that we actually perform no test on blobs, as you pointed out, except for the implicit one: read it as a blob object.

And reading them even only partially would still imply a lot of I/O, taking away much of the performance improvement I wanted to achieve here.

Further, please note that the `--quick` option *solely* impacts `git fsck`, not `git receive-pack`, because we actually really skipped everything except the connectivity test.

To allow this discussion to be resolved without further ado, I therefore renamed the `--quick` option to `--connectivity-only`, as even I realize that there is not much of a check left if not even author or committer lines are tested.

Ciao,
Dscho