Re: [PATCH] describe: Don’t look up commits with --exact-match

From: Thomas Rast <trast@student.ethz.ch>
Date: Dec 6, 2010, 10:53 UTC
Message-ID: <201012061153.59635.trast@student.ethz.ch>
In-Reply-To: <20101206073214.GA3745@burratino>

Jonathan Nieder wrote:

Show 11 quoted lines

> Anders Kaseorg wrote:
> > On Fri, 3 Dec 2010, Jonathan Nieder wrote:
> 
> >> Instead of looking up the commit to be matched exactly in the commits
> >> hash table, this makes a linear search.
> [...]
> > I don’t think it’s ever a problem: in my repository with 1800 tags on a 
> > warm cache, that loop accounts for about 0.1% of even the fastest 
> > non-exact-match query (a commit right after a tag).
> 
> Thanks for checking.  Makes sense.

Apart from measuring: for_each_ref *loads* the tags in a linear scan, so another linear scan doesn't add to the runtime w.r.t. number of tags. It only hurts if you also describe many refs in one go.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch