[notmuch] nested tag trees (was: Mail in git)

[Michal Sojka]

On Fri, 19 Feb 2010 13:31:15 +1300, martin f krafft <madduck at madduck.net> wrote:
> also sprach Ben Gamari <bgamari at gmail.com> [2010.02.18.1810 +1300]:
> > > Instead of nested subtrees, think of 16 subtrees forming
> > > a level-1 hash table, or 256 for level-2, which really *ought*
> > > to be enough.
> > > 
> > > Anyway, rewriting a tree object is pretty much exactly the same
> > > as removing a line (e.g. a message ID) from a file (e.g. a tag),
> > > as that file would have to be fully rewritten.
> > > 
> > This is very true, but exactly do you mean by this statement?
> 
> That any form of tag-to-message mapping will be expensive when you
> have a million messages referenced. If you used symlinks like mairix
> does, any manipulation would require changes to the directory index,
> which — curiously — functions much like the subtree approach you
> proposed.

Why do you want to store tag-to-message mapping in git? This is IMHO
perfectly solved by Xapian so storing message-to-tag mapping would be
sufficient, wouldn't it?

Michal