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import re
from functools import partial
from django.contrib.gis.db.models import aggregates
class BaseSpatialFeatures(object):
gis_enabled = True
# Does the database contain a SpatialRefSys model to store SRID information?
has_spatialrefsys_table = True
# Does the backend support the django.contrib.gis.utils.add_srs_entry() utility?
supports_add_srs_entry = True
# Does the backend introspect GeometryField to its subtypes?
supports_geometry_field_introspection = True
# Does the backend support storing 3D geometries?
supports_3d_storage = False
# Reference implementation of 3D functions is:
# https://postgis.net/docs/PostGIS_Special_Functions_Index.html#PostGIS_3D_Functions
supports_3d_functions = False
# Does the database support SRID transform operations?
supports_transform = True
# Do geometric relationship operations operate on real shapes (or only on bounding boxes)?
supports_real_shape_operations = True
# Can geometry fields be null?
supports_null_geometries = True
# Are empty geometries supported?
supports_empty_geometries = False
# Can the the function be applied on geodetic coordinate systems?
supports_distance_geodetic = True
supports_length_geodetic = True
supports_perimeter_geodetic = False
supports_area_geodetic = True
# Is the database able to count vertices on polygons (with `num_points`)?
supports_num_points_poly = True
# The following properties indicate if the database backend support
# certain lookups (dwithin, left and right, relate, ...)
supports_distances_lookups = True
supports_left_right_lookups = False
# Does the database have raster support?
supports_raster = False
# Does the database support a unique index on geometry fields?
supports_geometry_field_unique_index = True
@property
def supports_bbcontains_lookup(self):
return 'bbcontains' in self.connection.ops.gis_operators
@property
def supports_contained_lookup(self):
return 'contained' in self.connection.ops.gis_operators
@property
def supports_crosses_lookup(self):
return 'crosses' in self.connection.ops.gis_operators
@property
def supports_dwithin_lookup(self):
return 'dwithin' in self.connection.ops.gis_operators
@property
def supports_relate_lookup(self):
return 'relate' in self.connection.ops.gis_operators
@property
def supports_isvalid_lookup(self):
return 'isvalid' in self.connection.ops.gis_operators
# For each of those methods, the class will have a property named
# `has_<name>_method` (defined in __init__) which accesses connection.ops
# to determine GIS method availability.
geoqueryset_methods = (
'area', 'bounding_circle', 'centroid', 'difference', 'distance',
'distance_spheroid', 'envelope', 'force_rhr', 'geohash', 'gml',
'intersection', 'kml', 'length', 'mem_size', 'num_geom', 'num_points',
'perimeter', 'point_on_surface', 'reverse', 'scale', 'snap_to_grid',
'svg', 'sym_difference', 'transform', 'translate', 'union', 'unionagg',
)
# Is the aggregate supported by the database?
@property
def supports_collect_aggr(self):
return aggregates.Collect not in self.connection.ops.disallowed_aggregates
@property
def supports_extent_aggr(self):
return aggregates.Extent not in self.connection.ops.disallowed_aggregates
@property
def supports_make_line_aggr(self):
return aggregates.MakeLine not in self.connection.ops.disallowed_aggregates
@property
def supports_union_aggr(self):
return aggregates.Union not in self.connection.ops.disallowed_aggregates
def __init__(self, *args):
super(BaseSpatialFeatures, self).__init__(*args)
for method in self.geoqueryset_methods:
# Add dynamically properties for each GQS method, e.g. has_force_rhr_method, etc.
setattr(self.__class__, 'has_%s_method' % method,
property(partial(BaseSpatialFeatures.has_ops_method, method=method)))
def __getattr__(self, name):
m = re.match(r'has_(\w*)_function$', name)
if m:
func_name = m.group(1)
return func_name not in self.connection.ops.unsupported_functions
raise AttributeError
def has_ops_method(self, method):
return getattr(self.connection.ops, method, False)
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