[Xapian-discuss] 1.2.2/3 performance issue

[Markus Wörle]

Am 21.09.2010 um 15:55 schrieb 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.

Yep, it returns performance. After applying your patch on xapian-core-1.2.3, it's again as fast as versions < r14613.