[PATCH] allow to not sort the search results

[Sebastian Spaeth]

On 2010-04-15, Olly Betts wrote:
 
> > I would be happy to have it called --sort=relevance too, the unsorted
> > points out potential performance improvements a bit better, IMHO
> > (although they seem to be really small with a warm cache).
> 
> When using the results of a search to add/remove tags, there's likely to be
> an additional win from --sort=unsorted as documents will now be processed
> in docid order which will tend to have a more cache friendly locality of
> access.

Olly was right in that even for "notmuch tag" we were sorting the
results by date before applying tag changes. I have slightly reworked my
patch to have notmuch tag avoid doing that. I also split up the patch in
3 patches that do one thing each.

The patches do:
1: Introduce NOTMUCH_SORT_UNSORTED
2: Introduce notmuch search --sort=unsorted
3: Make notmuch tag not sort results by date

#2 is the one I am least sure about, I don't know if there is a use case
for notmuch search returning unsorted results. But 1 & 3 are useful at
least.
 
> Also, sorting by relevance requires more calculations and may require fetching
> additional data (document length for example).
> 
> So I think it would make sense for --sort=relevance and --sort=unsorted to be
> separate options.

Now I am a bit confused. The API docs state that sort_by_relevance is
the default. So by skipping any sort_by_value() will that incur the additional
calculations (with our BoolWeight set?). All I want is the fasted way
to return a searched set of docs :-).

Patches 1-3 follow as reply to this one
Sebastian