Re: [PATCH] Make reflog query '@{1219188291}' act as '@{2008/08/19 16:24:51}'

From: Shawn O. Pearce <spearce@spearce.org>
Date: Aug 20, 2008, 20:00 UTC
Message-ID: <20080820200026.GK3483@spearce.org>
In-Reply-To: <20080820195401.GD16626@blimp.local>

Alex Riesen <raa.lkml@gmail.com> wrote:

Show 10 quoted lines

> Shawn O. Pearce, Wed, Aug 20, 2008 21:44:07 +0200:
> > 
> > We could pick any number for the limit, just so long as its so
> > large that the size of the reflog for it to be a valid @{nth}
> > request would be something like 1 TB, and thus be highly unlikely.
> > 
> > I was just trying to be cute by using the original commit timestamp
> > of Git itself.  Perhaps 12936648 (1TB / 83)?
> 
> How about the maximum value the platform's size_t can handle?

So on 64 bit platforms we need to wait for another 2.92277266
x10^10 years before we will ever see a seconds-since-epoch which
can't possibly be mistaken for a position in the relfog file?

> Not because it is "highly unlikely", but because you and me frankly
> have no idea exactly how unlikely for example a "12936648 terabytes" is?

I have half a brain. Creating 12 million reflog entries would typically require 12 million git-update-ref forks. Anyone who is doing that many since reflog was introduced and has not yet truncated their reflog _really_ should reconsider what they are using it for.

Evaluating foo@{12936648} will be _horribly_ expensive. Anyone who is waiting for that result and _cares_ about it would have already started asking on the list for a reflog which is not based on a flat file. If they have already patched their Git to use something else (e.g. gdbm) I have no pity for them when this changes/breaks as they clearly have already patched their Git rather heavily.

-- 
Shawn.