from collections import defaultdict, namedtuple from contextlib import suppress from django.contrib.gis import forms, gdal from django.contrib.gis.db.models.proxy import SpatialProxy from django.contrib.gis.gdal.error import GDALException from django.contrib.gis.geometry.backend import Geometry, GeometryException from django.core.exceptions import ImproperlyConfigured from django.db.models.fields import Field from django.utils.translation import gettext_lazy as _ # Local cache of the spatial_ref_sys table, which holds SRID data for each # spatial database alias. This cache exists so that the database isn't queried # for SRID info each time a distance query is constructed. _srid_cache = defaultdict(dict) SRIDCacheEntry = namedtuple('SRIDCacheEntry', ['units', 'units_name', 'spheroid', 'geodetic']) def get_srid_info(srid, connection): """ Return the units, unit name, and spheroid WKT associated with the given SRID from the `spatial_ref_sys` (or equivalent) spatial database table for the given database connection. These results are cached. """ from django.contrib.gis.gdal import SpatialReference global _srid_cache try: # The SpatialRefSys model for the spatial backend. SpatialRefSys = connection.ops.spatial_ref_sys() except NotImplementedError: SpatialRefSys = None alias, get_srs = ( (connection.alias, lambda srid: SpatialRefSys.objects.using(connection.alias).get(srid=srid).srs) if SpatialRefSys else (None, SpatialReference) ) if srid not in _srid_cache[alias]: srs = get_srs(srid) units, units_name = srs.units _srid_cache[alias][srid] = SRIDCacheEntry( units=units, units_name=units_name, spheroid='SPHEROID["%s",%s,%s]' % (srs['spheroid'], srs.semi_major, srs.inverse_flattening), geodetic=srs.geographic, ) return _srid_cache[alias][srid] class GeoSelectFormatMixin: def select_format(self, compiler, sql, params): """ Return the selection format string, depending on the requirements of the spatial backend. For example, Oracle and MySQL require custom selection formats in order to retrieve geometries in OGC WKT. For all other fields, return a simple '%s' format string. """ connection = compiler.connection if connection.ops.select: # This allows operations to be done on fields in the SELECT, # overriding their values -- used by the Oracle and MySQL # spatial backends to get database values as WKT. sql = connection.ops.select % sql return sql, params class BaseSpatialField(Field): """ The Base GIS Field. It's used as a base class for GeometryField and RasterField. Defines properties that are common to all GIS fields such as the characteristics of the spatial reference system of the field. """ description = _("The base GIS field.") empty_strings_allowed = False def __init__(self, verbose_name=None, srid=4326, spatial_index=True, **kwargs): """ The initialization function for base spatial fields. Takes the following as keyword arguments: srid: The spatial reference system identifier, an OGC standard. Defaults to 4326 (WGS84). spatial_index: Indicates whether to create a spatial index. Defaults to True. Set this instead of 'db_index' for geographic fields since index creation is different for geometry columns. """ # Setting the index flag with the value of the `spatial_index` keyword. self.spatial_index = spatial_index # Setting the SRID and getting the units. Unit information must be # easily available in the field instance for distance queries. self.srid = srid # Setting the verbose_name keyword argument with the positional # first parameter, so this works like normal fields. kwargs['verbose_name'] = verbose_name super().__init__(**kwargs) def deconstruct(self): name, path, args, kwargs = super().deconstruct() # Always include SRID for less fragility; include spatial index if it's # not the default value. kwargs['srid'] = self.srid if self.spatial_index is not True: kwargs['spatial_index'] = self.spatial_index return name, path, args, kwargs def db_type(self, connection): return connection.ops.geo_db_type(self) def spheroid(self, connection): return get_srid_info(self.srid, connection).spheroid def units(self, connection): return get_srid_info(self.srid, connection).units def units_name(self, connection): return get_srid_info(self.srid, connection).units_name def geodetic(self, connection): """ Return true if this field's SRID corresponds with a coordinate system that uses non-projected units (e.g., latitude/longitude). """ return get_srid_info(self.srid, connection).geodetic def get_placeholder(self, value, compiler, connection): """ Return the placeholder for the spatial column for the given value. """ return connection.ops.get_geom_placeholder(self, value, compiler) def get_srid(self, obj): """ Return the default SRID for the given geometry or raster, taking into account the SRID set for the field. For example, if the input geometry or raster doesn't have an SRID, then the SRID of the field will be returned. """ srid = obj.srid # SRID of given geometry. if srid is None or self.srid == -1 or (srid == -1 and self.srid != -1): return self.srid else: return srid def get_db_prep_save(self, value, connection): """ Prepare the value for saving in the database. """ if isinstance(value, Geometry) or value: return connection.ops.Adapter(self.get_prep_value(value)) else: return None def get_raster_prep_value(self, value, is_candidate): """ Return a GDALRaster if conversion is successful, otherwise return None. """ if isinstance(value, gdal.GDALRaster): return value elif is_candidate: with suppress(GDALException): return gdal.GDALRaster(value) elif isinstance(value, dict): try: return gdal.GDALRaster(value) except GDALException: raise ValueError("Couldn't create spatial object from lookup value '%s'." % value) def get_prep_value(self, value): obj = super().get_prep_value(value) # When the input is not a geometry or raster, attempt to construct one # from the given string input. if isinstance(obj, Geometry): pass else: # Check if input is a candidate for conversion to raster or geometry. is_candidate = isinstance(obj, (bytes, str)) or hasattr(obj, '__geo_interface__') # Try to convert the input to raster. raster = self.get_raster_prep_value(obj, is_candidate) if raster: obj = raster elif is_candidate: try: obj = Geometry(obj) except (GeometryException, GDALException): raise ValueError("Couldn't create spatial object from lookup value '%s'." % obj) else: raise ValueError('Cannot use object with type %s for a spatial lookup parameter.' % type(obj).__name__) # Assigning the SRID value. obj.srid = self.get_srid(obj) return obj class GeometryField(GeoSelectFormatMixin, BaseSpatialField): """ The base Geometry field -- maps to the OpenGIS Specification Geometry type. """ description = _("The base Geometry field -- maps to the OpenGIS Specification Geometry type.") form_class = forms.GeometryField # The OpenGIS Geometry name. geom_type = 'GEOMETRY' def __init__(self, verbose_name=None, dim=2, geography=False, *, extent=(-180.0, -90.0, 180.0, 90.0), tolerance=0.05, **kwargs): """ The initialization function for geometry fields. In addition to the parameters from BaseSpatialField, it takes the following as keyword arguments: dim: The number of dimensions for this geometry. Defaults to 2. extent: Customize the extent, in a 4-tuple of WGS 84 coordinates, for the geometry field entry in the `USER_SDO_GEOM_METADATA` table. Defaults to (-180.0, -90.0, 180.0, 90.0). tolerance: Define the tolerance, in meters, to use for the geometry field entry in the `USER_SDO_GEOM_METADATA` table. Defaults to 0.05. """ # Setting the dimension of the geometry field. self.dim = dim # Is this a geography rather than a geometry column? self.geography = geography # Oracle-specific private attributes for creating the entry in # `USER_SDO_GEOM_METADATA` self._extent = extent self._tolerance = tolerance super().__init__(verbose_name=verbose_name, **kwargs) def deconstruct(self): name, path, args, kwargs = super().deconstruct() # Include kwargs if they're not the default values. if self.dim != 2: kwargs['dim'] = self.dim if self.geography is not False: kwargs['geography'] = self.geography return name, path, args, kwargs def get_db_prep_value(self, value, connection, *args, **kwargs): return connection.ops.Adapter( super().get_db_prep_value(value, connection, *args, **kwargs), **({'geography': True} if self.geography else {}) ) def from_db_value(self, value, expression, connection, context): if value: value = Geometry(value) srid = value.srid if not srid and self.srid != -1: value.srid = self.srid return value def contribute_to_class(self, cls, name, **kwargs): super().contribute_to_class(cls, name, **kwargs) # Setup for lazy-instantiated Geometry object. setattr(cls, self.attname, SpatialProxy(Geometry, self)) def formfield(self, **kwargs): defaults = {'form_class': self.form_class, 'geom_type': self.geom_type, 'srid': self.srid, } defaults.update(kwargs) if (self.dim > 2 and 'widget' not in kwargs and not getattr(defaults['form_class'].widget, 'supports_3d', False)): defaults['widget'] = forms.Textarea return super().formfield(**defaults) # The OpenGIS Geometry Type Fields class PointField(GeometryField): geom_type = 'POINT' form_class = forms.PointField description = _("Point") class LineStringField(GeometryField): geom_type = 'LINESTRING' form_class = forms.LineStringField description = _("Line string") class PolygonField(GeometryField): geom_type = 'POLYGON' form_class = forms.PolygonField description = _("Polygon") class MultiPointField(GeometryField): geom_type = 'MULTIPOINT' form_class = forms.MultiPointField description = _("Multi-point") class MultiLineStringField(GeometryField): geom_type = 'MULTILINESTRING' form_class = forms.MultiLineStringField description = _("Multi-line string") class MultiPolygonField(GeometryField): geom_type = 'MULTIPOLYGON' form_class = forms.MultiPolygonField description = _("Multi polygon") class GeometryCollectionField(GeometryField): geom_type = 'GEOMETRYCOLLECTION' form_class = forms.GeometryCollectionField description = _("Geometry collection") class ExtentField(GeoSelectFormatMixin, Field): "Used as a return value from an extent aggregate" description = _("Extent Aggregate Field") def get_internal_type(self): return "ExtentField" class RasterField(BaseSpatialField): """ Raster field for GeoDjango -- evaluates into GDALRaster objects. """ description = _("Raster Field") geom_type = 'RASTER' geography = False def _check_connection(self, connection): # Make sure raster fields are used only on backends with raster support. if not connection.features.gis_enabled or not connection.features.supports_raster: raise ImproperlyConfigured('Raster fields require backends with raster support.') def db_type(self, connection): self._check_connection(connection) return super().db_type(connection) def from_db_value(self, value, expression, connection, context): return connection.ops.parse_raster(value) def contribute_to_class(self, cls, name, **kwargs): super().contribute_to_class(cls, name, **kwargs) # Setup for lazy-instantiated Raster object. For large querysets, the # instantiation of all GDALRasters can potentially be expensive. This # delays the instantiation of the objects to the moment of evaluation # of the raster attribute. setattr(cls, self.attname, SpatialProxy(gdal.GDALRaster, self)) def get_transform(self, name): from django.contrib.gis.db.models.lookups import RasterBandTransform try: band_index = int(name) return type( 'SpecificRasterBandTransform', (RasterBandTransform, ), {'band_index': band_index} ) except ValueError: pass return super().get_transform(name)