[Xapian-discuss] 1.2.2/3 performance issue

[Olly Betts]

On Wed, Sep 01, 2010 at 03:17:20PM +0200, Markus Wörle wrote:
> 
> Am 31.08.2010 um 15:56 schrieb Olly Betts:
> > Nothing else looks likely.  There are a couples of correctness fixes (tickets
> > #475 and #476) but I'd be surprised if they had such a drastic effect.
> > 
> > You could try 1.2.1, but there were a lot of changes between 1.2.0 and 1.2.1
> > and not many between 1.2.1 and 1.2.2, so it's likely 1.2.1 is affected too.
> > 
> > Beyond hat you could try a binary chop on SVN to find where this started if
> > you have a simple case to check each time.
> 
> Did that (took a while). It turned out that revision 14612 and below are
> fast, whereas 14613 and above are slow.
> 
> So it's http://trac.xapian.org/changeset/14613 where it happens.

Thanks for narrowing that down so precisely - very much appreciated.

This is another correctness fix, but for an optimisation added after 1.2.0,
so there's something odd going on here.  I guess either the original
optimisation doesn't actually help once made to work correctly (at least in
some common cases) or there's collateral damage in the fix.

I'll take a deeper look.

Cheers,
    Olly