Xapian discuss - Jul 2010 - Spelling correction confusion

If I spell "commission" wrongly with an s instead of a t, Xapian (via
the QueryParser's get_corrected_query_string function) is finding
the right spelling:

http://www.whatdotheyknow.com/search/commistion

However, if I miss the s out completely, it doesn't find it:

http://www.whatdotheyknow.com/search/commision

Any idea why that is?

Missing the last i out also doesn't work:
    http://www.whatdotheyknow.com/search/commisson
But if I miss the last o out, it finds the right spelling:
    http://www.whatdotheyknow.com/search/commissin

Reading the algorithm here, I can't see why this would be...
    http://xapian.org/docs/spelling.html

Any suggestions? Even just ideas for debugging it would be great.

Thanks for your help,

Francis

On Wed, Jul 28, 2010 at 05:55:37PM +0100, Francis Irving
wrote:
> If I spell "commission" wrongly with an s instead of a t, Xapian
(via
> the QueryParser's get_corrected_query_string function) is finding
> the right spelling:
> 
> http://www.whatdotheyknow.com/search/commistion
Hmm, this returns two matches, but neither seems to have "commistion"
in
(or anything which might stem to it).
> However, if I miss the s out completely, it doesn't find it:
> 
> http://www.whatdotheyknow.com/search/commision
> 
> Any idea why that is?
Probably it's this issue:

http://trac.xapian.org/ticket/225

I'm puzzled by the two apparent matches, but if there was a word with the
same stemmed form as "commistion" in those documents you would see
this
behaviour, so I guess it is there but in some text not visible in the
view shown.

Cheers,
    Olly