Re: [GSoC] Designing a faster index format

On Wed, Mar 21, 2012 at 6:08 PM, Thomas Gummerer [off-list ref] wrote:

quoted

quoted

However I got one more question, since I'm not yet really familiar with
the
code and internal structure of git, what exactly does the SHA1 over the
index exactly achieve? Is it only for checking if the index is still
correct
for the next time it is used and has not been changed or is there a more
important function of it?

It makes sure the index is not corrupt (by disk faults for example). I
don't think it is used for anything else. Cheaper checksum can be used
if good enough for the index. See
http://thread.gmane.org/gmane.comp.version-control.git/190016 and the
following reply.

Ok thanks. I guess that could be another way to speed things up, but for
really big repositories probably it won't be enough and the reduction of the
complexity as described in the proposal is the way to go.

Yeah. A good format should not require checksuming the whole index, if
we only need to read/verify a few entries, I think.

Is the current complexity O(n)?

I think so. Have a look at read-cache.c, read_index_from for reading
and write_index for writing, as a starting point.
-- 
Duy