Hi,
I've managed to make my spatial queries work. But it's the most cost
inefficient way possible. All the calculations are being done by code
and not by the database itself. Case (a) below works but I think it
retrieves all rows from my table and then calculates and filters it.
Case (b) that doesn't work would be the ideal for me.
case (a) -- WORKS!
ICriteria criteria = Session.CreateCriteria(typeof(T));
return (from t in criteria.List<T>()
where t.GetLocation().GetDistance(location) <=
radius
select t).ToList<T>();
case (b) -- DOES NOT WORK!!
return (from t in Session.Query<T>()
where t.GetLocation().GetDistance(location) <=
radius
select t).ToList<T>();
Throws:
NHibernateMappings.Testing.NHibernateMappingTest.FindByVicinity:
System.NotSupportedException : Double
GetDistance(NHibernateMappings.Model.Location)
Now I think this goes back to my original question. How do I map the
function so that I make my case (b) work? Is it even possible?
Any help is greatly appreciated,
Thanks in advance,
Marcelo Grossi
On Apr 13, 7:32 pm, TheCPUWizard <[email protected]> wrote:
> Some databases now have built in support so that what you are looking for
> can be done completely DB server side....
>
>
>
>
>
>
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf
>
> Of Marcelo Grossi
> Sent: Friday, April 13, 2012 2:56 PM
> To: nhusers
> Subject: [nhusers] Mapping a scalar function?
>
> Hi all,
>
> I need a, very common nowadays, distance from locations filter. I have a
> resource that has an address that itself have lat and long properties. I
> also have a base location that I want to compare against all the resources
> locations and filter out those who are at most "radius" meters distant from
> my base location.
>
> I would like to use the linq notation to be consistent throughout my
> project. I found out that you can re-write the SqlDialect to support a new
> function. My question is: is this the only way or is there some special
> mapping that I can make in order to map a function in my object to a
> database filter call. Like so:
>
> from r in Resource
> where r.DistanceFromLocation(constant_input_location) <=
> constant_input_radius select r...
>
> This way in my entity mapping class (I'm using the Map By Code approach in
> NH 3.2) I would simply map my function as if it were a property. Like so:
>
> Property(...);
> CustomFunction(x => x.DistanceFromLocation, m => m...);
>
> I'm really new to both NHibernate and Mapping By Code so please bear with my
> ignorance. Am I dreaming here or is this actually possible?
>
> Sorry in advance if this is too far-fetched. The thing is that NH does
> everything I need and more so why not this? :-)
>
> Thanks in advance is anyone has any idea on the subject.
>
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