使用NHibernate和SQL Server Geography进行距离高级搜索 [英] Advanced search with distances using NHibernate and SQL Server Geography

问题描述

我在存储库中有一个现有的高级搜索方法，该方法可以检查FormCollection是否存在搜索条件，如果存在，则将条件添加到搜索中，例如

I've got an existing advanced search method in a repository that checks a FormCollection for the existence of search criteria, and if present, adds a criterion to the search e.g.

public IList<Residence> GetForAdvancedSearch(FormCollection collection)
{
  var criteria = Session.CreateCriteria(typeof(Residence))
    .SetResultTransformer(new DistinctRootEntityResultTransformer());

  if (collection["MinBedrooms"] != null)
  {
    criteria
      .Add(Restrictions.Ge("Bedrooms", int.Parse(collection["MinBedrooms"])));
  }

  // ... many criteria omitted for brevity

  return criteria.List<Residence>();
}

我还进行了基本的距离搜索，以查找每个住宅与搜索条件之间的距离.查询的HBM为

I've also got a basic distance search to find how far each residence is from the search criteria. The HBM for the query is

<sql-query name="Residence.Nearest">
  <return alias="residence" class="Residences.Domain.Residence, Residences"/>
  <return-scalar column="Distance" type="float"/>
  SELECT R.*, dbo.GetDistance(:point, R.Coordinate) AS Distance
  FROM Residence R
  WHERE Distance < 10
  ORDER BY Distance
</sql-query>

我必须定义一个计算距离的函数，因为在地理函数中无法让NHibernate逃避结肠:

I had to define a function to calculate the distance, as there was no way to get NHibernate to escape the colons in the geography function:

 CREATE FUNCTION dbo.GetDistance
 (
  @firstPoint nvarchar(100), 
  @secondPoint GEOMETRY
 )
 RETURNS float
 AS
 BEGIN
  RETURN GEOGRAPHY::STGeomFromText(
  @firstPoint, 4326).STDistance(@secondPoint.STAsText()) / 1609.344
 END

存储库将这样调用命名查询:

And the repository calls the named query thus:

return Session
   .GetNamedQuery("Residence.Nearest")
   .SetString("point", String.Format("POINT({0} {1})", latitude, longitude))
   .List();

所以我的问题是；如何将两者结合在一起(或从头开始)，以便可以过滤高级搜索结果，使其仅包括距离搜索位置10英里以内的住所?

So my question is; how do I combine the two (or start from scratch), so I can filter the advanced search results to include only residences within 10 miles of the search location?

更新我已经尝试通过以下代码使用NHibernate.Spatial:

UPDATE I have tried using NHibernate.Spatial with the following code:

criteria.Add(SpatialExpression.IsWithinDistance(
    "Coordinate", new Coordinate(latitude, longitude), 10));

但SpatialExpression.IsWithinDistance返回了System.NotImplementedException.

推荐答案

创建一个投影，该投影实际上会在结果中添加一个新的距离列，该距离列是由UDF计算得出的，然后对其添加了限制:

Create a projection that, in effect, adds a new distance column to the results, which is calculated by called the UDF, and then add a restriction to it:

var query = String.Format(
    "dbo.GetDistance('POINT({0} {1}', Coordinate) AS Distance", 
    latitude, longitude);
criteria
    .Add(Restrictions.Le(Projections.SqlProjection(
        query, 
        new [] {"Distance"}, 
        new [] {NHibernateUtil.Double}), 10));

更新

n.b.尽管在我发布该消息时一定有效，但是它不再起作用. NHibernate不喜欢'.'. dbo之后，并说

n.b. Although this must have worked when I posted it, it doesn't work any more. NHibernate doesn't like the '.' after dbo, and says

无法解析属性:Residences.Domain.Residence的dbo".

"could not resolve property: dbo of: Residences.Domain.Residence".

如果我删除"dbo".我得到

If I remove the 'dbo.' I get

'GetDistance'不是公认的内置函数名称."

"'GetDistance' is not a recognized built-in function name."

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