地理空间&google appengine python中基于位置的搜索 [英] geoSpatial & Location based search in google appengine python

问题描述

我想在airbnb(https://www.airbnb.com/s/Paris--France?source=ds&page=1&s_tag=PNoY_mlz&allow_override%5B%5D=)

I want to achieve something like the map drag search on airbnb (https://www.airbnb.com/s/Paris--France?source=ds&page=1&s_tag=PNoY_mlz&allow_override%5B%5D=)

我将这样的数据保存在数据存储区

I am saving the data like this in datastore

 user.lat = float(lat)
     user.lon = float(lon)
     user.geoLocation = ndb.GeoPt(float(lat),float(lon))

每当我拖动 &放下地图或放大或缩小我在控制器中获得以下参数

and whenever I drag & drop map or zoom in or zoom out I get following parameters in my controller

    def get(self):
    """
    This is an ajax function. It gets the place name, north_east, and south_west
    coordinates. Then it fetch the results matching the search criteria and
    create a result list. After that it returns the result in json format.
    :return: result
    """
    self.response.headers['Content-type'] = 'application/json'
    results = []
    north_east_latitude = float(self.request.get('nelat'))
    north_east_longitude = float(self.request.get('nelon'))
    south_west_latitude = float(self.request.get('swlat'))
    south_west_longitude = float(self.request.get('swlon'))
    points = Points.query(Points.lat<north_east_latitude,Points.lat>south_west_latitude)
    for row in points:
        if  row.lon > north_east_longitude and row.lon < south_west_longitude:
            listingdic = {'name': row.name, 'desc': row.description, 'contact': row.contact, 'lat': row.lat, 'lon': row.lon}
            results.append(listingdic)
    self.write(json.dumps({'listings':results}))

我的模型类如下

class Points(ndb.Model):
    name = ndb.StringProperty(required=True)
    description = ndb.StringProperty(required=True)
    contact = ndb.StringProperty(required=True)
    lat = ndb.FloatProperty(required=True)
    lon = ndb.FloatProperty(required=True)
    geoLocation = ndb.GeoPtProperty()

我想改进查询.

提前致谢.

推荐答案

否，您无法通过检查查询中的所有 4 个条件来改进解决方案，因为 ndb 查询不支持多个属性的不等式过滤器.来自 NDB 查询(重点是我的):

No, you cannot improve the solution by checking all 4 conditions in the query because ndb queries do not support inequality filters on multiple properties. From NDB Queries (emphasis mine):

限制:数据存储区对查询实施了一些限制.违反这些将导致它引发异常.例如，组合太多过滤器，对多个使用不等式属性，或将不等式与排序顺序组合在一起不同的财产目前都被禁止.还有过滤器引用多个属性有时需要二级索引进行配置.

Limitations: The Datastore enforces some restrictions on queries. Violating these will cause it to raise exceptions. For example, combining too many filters, using inequalities for multiple properties, or combining an inequality with a sort order on a different property are all currently disallowed. Also filters referencing multiple properties sometimes require secondary indexes to be configured.

和

注意:如前所述，数据存储区拒绝对多个属性使用不等式过滤的查询.

Note: As mentioned earlier, the Datastore rejects queries using inequality filtering on more than one property.

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