[Geocoding] Word order in query

[Dariusz Bączkowski]

Dnia czwartek, 6 czerwca 2013 o 07:50:38 Sarah Hoffmann napisał(a):
> Hi,
> 
> On Sat, Jun 01, 2013 at 04:47:08PM +0200, Dariusz Bączkowski wrote:
> > Hello,
> > 
> > I have noticed strange behavior on Nominatim. In some queries word
> > ordering do not have impact on results in some it has. Below are 2
> > examples of this inconsistency. Should this queries return identical
> > results? Is this a bug or there is some architectural explanation for
> > it? Can it be fixed?
> 
> It is more of an architectural thing. To Nominatim, these two queries are
> vastly different. One is a search for a full name ("Konstantego Ildefonsa
> Gałczyńskiego" is tagged exactly like that), for the other one it has to
> look for partial matchings because it has the name backwards in its
> database. To keep the search load acceptable, Nominatim doesn't go through
> all potential partial matchings, so wether or not you get a result depends
> on how far down the list the right query is.
> 
> To see what I mean have a look at the debug output:
> (1)
> http://nominatim.openstreetmap.org/search.php?q=Ga%C5%82czy%C5%84skiego+Ko
> nstantego+Ildefonsa%2C+Koszalin&debug=1 (2)
> http://nominatim.openstreetmap.org/search.php?q=Wyszy%C5%84skiego+Kardyna%
> C5%82a+Stefana%2C+Koszalin&debug=1
> 
> You can ignore most of the noise. Just have a look at the large table, it
> contains the final queries that are sent to the DB. The query that would
> return a result is in both cases the one with the three parts in the name
> column (a partial query made up of three single words is needed). For (2)
> that query is at rank 6, so it will still be evaluated. In (1) it ended up
> at rank 7 (because there actually is a road called "Gałczyńskiego
> Konstantego Ildefonsa" somewhere even though it is not the one in
> Koszalin) and you can see below that Nominatim stops after rank 6.
> 
> There is certainly some room for improvement in the ranking of these search
> queries especially when it comes to partial searches but in the end it is
> always a question of weighing performance against completeness.

Is there a way to make it work on my local instance of Nominatim?
Some patch? Ideal will be option in settings, but I can change it manually in 
code. I do not think performance hit will be noticable for us.

> 
> Sarah
> 
> > Konstantego Ildefonsa Gałczyńskiego, Koszalin (RESULT)
> > http://nominatim.openstreetmap.org/search.php?q=Konstantego+Ildefonsa+Ga%
> > C5%82czy%C5%84skiego%2C+Koszalin&viewbox=-94.93%2C46.2%2C94.93%2C-46.2
> > 
> > Gałczyńskiego Konstantego Ildefonsa, Koszalin (NO RESULT)
> > http://nominatim.openstreetmap.org/search.php?q=Ga%C5%82czy%C5%84skiego+K
> > onstantego+Ildefonsa%2C+Koszalin&viewbox=16.18%2C54.2%2C16.2%2C54.19
> > 
> > Kardynała Stefana Wyszyńskiego, Koszalin (RESULT)
> > http://nominatim.openstreetmap.org/search.php?q=Kardyna%C5%82a+Stefana+Wy
> > szy%C5%84skiego%2C+Koszalin&viewbox=16.17%2C54.2%2C16.19%2C54.18
> > 
> > Wyszyńskiego Kardynała Stefana, Koszalin (RESULT)
> > http://nominatim.openstreetmap.org/search.php?q=Wyszy%C5%84skiego+Kardyna
> > %C5%82a+Stefana%2C+Koszalin&viewbox=-112.5%2C46.2%2C112.5%2C-46.2
> > 
> > 
> > 
> > 
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> > Geocoding at openstreetmap.org
> > http://lists.openstreetmap.org/listinfo/geocoding

-- 
Pozdrawiam,
Dariusz Bączkowski

ESYSCODER Dariusz Bączkowski
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