[Xapian-discuss] 1.2.2/3 performance issue

[Olly Betts]

On Thu, Sep 02, 2010 at 02:43:36AM +0100, Olly Betts wrote:
> On Wed, Sep 01, 2010 at 03:17:20PM +0200, Markus Wörle wrote:
> > Did that (took a while). It turned out that revision 14612 and below are
> > fast, whereas 14613 and above are slow.

> 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.

Looking deeper, I suspect that the optimisation is slower in some cases.

As a first step, can you test a "slow" version (anything >= r14613 - 1.2.3
is fine if that's easiest) with this patch:

http://oligarchy.co.uk/xapian/patches/orpostlist-check-disable.patch

If that returns performance to what you get with versions < r14613 then
I'll try to write a patch which doesn't just disable this optmisation.

Cheers,
    Olly