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'))
# 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.
srid = self.query.get_context('transformed_srid')
if srid:
u, unit_name, s = get_srid_info(srid, connection)
geodetic = unit_name.lower() in geo_field.geodetic_units
if geodetic and not connection.features.supports_distance_geodetic:
raise ValueError(
'This database does not support linear distance '
'calculations on geodetic coordinate systems.'
)
if distance:
if 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, srid)
if geom.srid is None or geom.srid == 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, 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, srid))
else:
procedure_fmt += ', %s(%%%%s, %s)' % (backend.transform, 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(six.memoryview(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 connection.features.supports_3d_functions:
# Use 3D variants of perimeter and length routines on supported backends.
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)
import warnings
