Date: Fri, 16 Apr 2010 07:58:14 +0100
From: Olly Betts <olly@survex.com>
To: Sebastian Spaeth <Sebastian@SSpaeth.de>
Subject: Re: [PATCH] allow to not sort the search results
Message-ID: <20100416065814.GO10323@survex.com>
References: <1271226655-5672-1-git-send-email-Sebastian@SSpaeth.de>
	<20100414065525.GA11770@jdc.jasonjgw.net>
	<87hbnebhg0.fsf@SSpaeth.de>
	<loom.20100415T144148-25@post.gmane.org>
	<87eiifj433.fsf@SSpaeth.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87eiifj433.fsf@SSpaeth.de>
User-Agent: Mutt/1.5.18 (2008-05-17)
Cc: notmuch@notmuchmail.org
Precedence: list

On Fri, Apr 16, 2010 at 08:37:04AM +0200, Sebastian Spaeth wrote:
> On 2010-04-15, Olly Betts wrote:
> > 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 :-).

Yes, sort_by_relevance() is the default.  But if you set BoolWeight as the
weighting scheme then the relevance is simply zero, and Xapian doesn't have
to fetch any statistics and calculate a score from them.  When documents
have exactly equal relevance weight, then the docid order is used.  So
although sort_by_relevance() is technically still on with BoolWeight, by
"sorting by relevance" I wasn't talking about this case.

So --sort=unsorted and --sort=relevance would only differ in code by the former
setting BoolWeight and the latter not.

Cheers,
    Olly