def get_distance(self, f, dist_val, lookup_type):
"""
Retrieve the distance parameters for the given geometry field,
distance lookup value, and the distance lookup type.
This is the most complex implementation of the spatial backends due to
what is supported on geodetic geometry columns vs. what's available on
projected geometry columns. In addition, it has to take into account
the newly introduced geography column type introudced in PostGIS 1.5.
"""
# Getting the distance parameter and any options.
if len(dist_val) == 1:
value, option = dist_val[0], None
else:
value, option = dist_val
# Shorthand boolean flags.
geodetic = f.geodetic(self.connection)
geography = f.geography and self.geography
if isinstance(value, Distance):
if geography:
dist_param = value.m
elif geodetic:
if lookup_type == 'dwithin':
raise ValueError('Only numeric values of degree units are '
'allowed on geographic DWithin queries.')
dist_param = value.m
else:
dist_param = getattr(value, Distance.unit_attname(f.units_name(self.connection)))
else:
# Assuming the distance is in the units of the field.
dist_param = value
if (not geography and geodetic and lookup_type != 'dwithin'
and option == 'spheroid'):
# using distance_spheroid requires the spheroid of the field as
# a parameter.
return [f._spheroid, dist_param]
else:
return [dist_param]
def get_distance(self, f, value, lookup_type):
"""
Returns the distance parameters for the given geometry field,
lookup value, and lookup type. SpatiaLite only supports regular
cartesian-based queries (no spheroid/sphere calculations for point
geometries like PostGIS).
"""
if not value:
return []
value = value[0]
if isinstance(value, Distance):
if f.geodetic(self.connection):
raise ValueError('SpatiaLite does not support distance queries on '
'geometry fields with a geodetic coordinate system. '
'Distance objects; use a numeric value of your '
'distance in degrees instead.')
else:
dist_param = getattr(value, Distance.unit_attname(f.units_name(self.connection)))
else:
dist_param = value
return [dist_param]
def get_distance(self, f, value, lookup_type):
"""
Returns the distance parameters given the value and the lookup type.
On Oracle, geometry columns with a geodetic coordinate system behave
implicitly like a geography column, and thus meters will be used as
the distance parameter on them.
"""
if not value:
return []
value = value[0]
if isinstance(value, Distance):
if f.geodetic(self.connection):
dist_param = value.m
else:
dist_param = getattr(value, Distance.unit_attname(f.units_name(self.connection)))
else:
dist_param = value
# dwithin lookups on oracle require a special string parameter
# that starts with "distance=".
if lookup_type == 'dwithin':
dist_param = 'distance=%s' % dist_param
return [dist_param]
def _distance_attribute(self, func, geom=None, tolerance=0.05, spheroid=False, **kwargs):
"""
DRY routine for GeoQuerySet distance attribute routines.
"""
# Setting up the distance procedure arguments.
procedure_args, geo_field = self._spatial_setup(func, field_name=kwargs.get('field_name', None))
# If geodetic defaulting distance attribute to meters (Oracle and
# PostGIS spherical distances return meters). Otherwise, use the
# units of the geometry field.
connection = connections[self.db]
geodetic = geo_field.geodetic(connection)
geography = geo_field.geography
if geodetic:
dist_att = 'm'
else:
dist_att = Distance.unit_attname(geo_field.units_name(connection))
# Shortcut booleans for what distance function we're using and
# whether the geometry field is 3D.
distance = func == 'distance'
length = func == 'length'
perimeter = func == 'perimeter'
if not (distance or length or perimeter):
raise ValueError('Unknown distance function: %s' % func)
geom_3d = geo_field.dim == 3
# The field's get_db_prep_lookup() is used to get any
# extra distance parameters. Here we set up the
# parameters that will be passed in to field's function.
lookup_params = [geom or 'POINT (0 0)', 0]
# Getting the spatial backend operations.
backend = connection.ops
# If the spheroid calculation is desired, either by the `spheroid`
# keyword or when calculating the length of geodetic field, make
# sure the 'spheroid' distance setting string is passed in so we
# get the correct spatial stored procedure.
if spheroid or (backend.postgis and geodetic and
(not geography) and length):
lookup_params.append('spheroid')
lookup_params = geo_field.get_prep_value(lookup_params)
params = geo_field.get_db_prep_lookup('distance_lte', lookup_params, connection=connection)
# The `geom_args` flag is set to true if a geometry parameter was
# passed in.
geom_args = bool(geom)
if backend.oracle:
if distance:
procedure_fmt = '%(geo_col)s,%(geom)s,%(tolerance)s'
elif length or perimeter:
procedure_fmt = '%(geo_col)s,%(tolerance)s'
procedure_args['tolerance'] = tolerance
else:
# Getting whether this field is in units of degrees since the field may have
# been transformed via the `transform` GeoQuerySet method.
if self.query.transformed_srid:
u, unit_name, s = get_srid_info(self.query.transformed_srid, connection)
geodetic = unit_name in geo_field.geodetic_units
if backend.spatialite and geodetic:
raise ValueError('SQLite does not support linear distance calculations on geodetic coordinate systems.')
if distance:
if self.query.transformed_srid:
# Setting the `geom_args` flag to false because we want to handle
# transformation SQL here, rather than the way done by default
# (which will transform to the original SRID of the field rather
# than to what was transformed to).
geom_args = False
procedure_fmt = '%s(%%(geo_col)s, %s)' % (backend.transform, self.query.transformed_srid)
if geom.srid is None or geom.srid == self.query.transformed_srid:
# If the geom parameter srid is None, it is assumed the coordinates
# are in the transformed units. A placeholder is used for the
# geometry parameter. `GeomFromText` constructor is also needed
# to wrap geom placeholder for SpatiaLite.
if backend.spatialite:
procedure_fmt += ', %s(%%%%s, %s)' % (backend.from_text, self.query.transformed_srid)
else:
procedure_fmt += ', %%s'
else:
# We need to transform the geom to the srid specified in `transform()`,
# so wrapping the geometry placeholder in transformation SQL.
# SpatiaLite also needs geometry placeholder wrapped in `GeomFromText`
# constructor.
if backend.spatialite:
procedure_fmt += ', %s(%s(%%%%s, %s), %s)' % (backend.transform, backend.from_text,
geom.srid, self.query.transformed_srid)
else:
procedure_fmt += ', %s(%%%%s, %s)' % (backend.transform, self.query.transformed_srid)
else:
# `transform()` was not used on this GeoQuerySet.
procedure_fmt = '%(geo_col)s,%(geom)s'
if not geography and geodetic:
# Spherical distance calculation is needed (because the geographic
# field is geodetic). However, the PostGIS ST_distance_sphere/spheroid()
# procedures may only do queries from point columns to point geometries
# some error checking is required.
if not backend.geography:
if not isinstance(geo_field, PointField):
raise ValueError('Spherical distance calculation only supported on PointFields.')
if not str(Geometry(buffer(params[0].ewkb)).geom_type) == 'Point':
raise ValueError('Spherical distance calculation only supported with Point Geometry parameters')
# The `function` procedure argument needs to be set differently for
# geodetic distance calculations.
if spheroid:
# Call to distance_spheroid() requires spheroid param as well.
procedure_fmt += ",'%(spheroid)s'"
procedure_args.update({'function' : backend.distance_spheroid, 'spheroid' : params[1]})
else:
procedure_args.update({'function' : backend.distance_sphere})
elif length or perimeter:
procedure_fmt = '%(geo_col)s'
if not geography and geodetic and length:
# There's no `length_sphere`, and `length_spheroid` also
# works on 3D geometries.
procedure_fmt += ",'%(spheroid)s'"
procedure_args.update({'function' : backend.length_spheroid, 'spheroid' : params[1]})
elif geom_3d and backend.postgis:
# Use 3D variants of perimeter and length routines on PostGIS.
if perimeter:
procedure_args.update({'function' : backend.perimeter3d})
elif length:
procedure_args.update({'function' : backend.length3d})
# Setting up the settings for `_spatial_attribute`.
s = {'select_field' : DistanceField(dist_att),
'setup' : False,
'geo_field' : geo_field,
'procedure_args' : procedure_args,
'procedure_fmt' : procedure_fmt,
}
if geom_args:
s['geom_args'] = ('geom',)
s['procedure_args']['geom'] = geom
elif geom:
# The geometry is passed in as a parameter because we handled
# transformation conditions in this routine.
s['select_params'] = [backend.Adapter(geom)]
return self._spatial_attribute(func, s, **kwargs)
