335 lines
12 KiB
Python
335 lines
12 KiB
Python
from django.db.models.fields import Field
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from django.db.models.sql.expressions import SQLEvaluator
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from django.utils.translation import ugettext_lazy as _
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from django.contrib.gis import forms
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from django.contrib.gis.db.models.constants import GIS_LOOKUPS
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from django.contrib.gis.db.models.lookups import GISLookup
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from django.contrib.gis.db.models.proxy import GeometryProxy
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from django.contrib.gis.geometry.backend import Geometry, GeometryException
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from django.utils import six
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# Local cache of the spatial_ref_sys table, which holds SRID data for each
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# spatial database alias. This cache exists so that the database isn't queried
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# for SRID info each time a distance query is constructed.
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_srid_cache = {}
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def get_srid_info(srid, connection):
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"""
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Returns the units, unit name, and spheroid WKT associated with the
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given SRID from the `spatial_ref_sys` (or equivalent) spatial database
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table for the given database connection. These results are cached.
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"""
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global _srid_cache
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try:
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# The SpatialRefSys model for the spatial backend.
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SpatialRefSys = connection.ops.spatial_ref_sys()
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except NotImplementedError:
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# No `spatial_ref_sys` table in spatial backend (e.g., MySQL).
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return None, None, None
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if connection.alias not in _srid_cache:
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# Initialize SRID dictionary for database if it doesn't exist.
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_srid_cache[connection.alias] = {}
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if srid not in _srid_cache[connection.alias]:
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# Use `SpatialRefSys` model to query for spatial reference info.
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sr = SpatialRefSys.objects.using(connection.alias).get(srid=srid)
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units, units_name = sr.units
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spheroid = SpatialRefSys.get_spheroid(sr.wkt)
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_srid_cache[connection.alias][srid] = (units, units_name, spheroid)
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return _srid_cache[connection.alias][srid]
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class GeometryField(Field):
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"The base GIS field -- maps to the OpenGIS Specification Geometry type."
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# The OpenGIS Geometry name.
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geom_type = 'GEOMETRY'
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form_class = forms.GeometryField
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# Geodetic units.
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geodetic_units = ('decimal degree', 'degree')
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description = _("The base GIS field -- maps to the OpenGIS Specification Geometry type.")
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def __init__(self, verbose_name=None, srid=4326, spatial_index=True, dim=2,
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geography=False, **kwargs):
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"""
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The initialization function for geometry fields. Takes the following
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as keyword arguments:
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srid:
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The spatial reference system identifier, an OGC standard.
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Defaults to 4326 (WGS84).
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spatial_index:
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Indicates whether to create a spatial index. Defaults to True.
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Set this instead of 'db_index' for geographic fields since index
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creation is different for geometry columns.
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dim:
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The number of dimensions for this geometry. Defaults to 2.
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extent:
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Customize the extent, in a 4-tuple of WGS 84 coordinates, for the
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geometry field entry in the `USER_SDO_GEOM_METADATA` table. Defaults
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to (-180.0, -90.0, 180.0, 90.0).
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tolerance:
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Define the tolerance, in meters, to use for the geometry field
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entry in the `USER_SDO_GEOM_METADATA` table. Defaults to 0.05.
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"""
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# Setting the index flag with the value of the `spatial_index` keyword.
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self.spatial_index = spatial_index
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# Setting the SRID and getting the units. Unit information must be
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# easily available in the field instance for distance queries.
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self.srid = srid
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# Setting the dimension of the geometry field.
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self.dim = dim
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# Setting the verbose_name keyword argument with the positional
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# first parameter, so this works like normal fields.
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kwargs['verbose_name'] = verbose_name
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# Is this a geography rather than a geometry column?
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self.geography = geography
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# Oracle-specific private attributes for creating the entry in
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# `USER_SDO_GEOM_METADATA`
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self._extent = kwargs.pop('extent', (-180.0, -90.0, 180.0, 90.0))
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self._tolerance = kwargs.pop('tolerance', 0.05)
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super(GeometryField, self).__init__(**kwargs)
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def deconstruct(self):
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name, path, args, kwargs = super(GeometryField, self).deconstruct()
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# Always include SRID for less fragility; include others if they're
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# not the default values.
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kwargs['srid'] = self.srid
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if self.dim != 2:
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kwargs['dim'] = self.dim
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if self.spatial_index is not True:
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kwargs['spatial_index'] = self.spatial_index
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if self.geography is not False:
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kwargs['geography'] = self.geography
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return name, path, args, kwargs
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# The following functions are used to get the units, their name, and
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# the spheroid corresponding to the SRID of the GeometryField.
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def _get_srid_info(self, connection):
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# Get attributes from `get_srid_info`.
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self._units, self._units_name, self._spheroid = get_srid_info(self.srid, connection)
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def spheroid(self, connection):
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if not hasattr(self, '_spheroid'):
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self._get_srid_info(connection)
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return self._spheroid
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def units(self, connection):
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if not hasattr(self, '_units'):
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self._get_srid_info(connection)
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return self._units
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def units_name(self, connection):
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if not hasattr(self, '_units_name'):
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self._get_srid_info(connection)
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return self._units_name
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### Routines specific to GeometryField ###
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def geodetic(self, connection):
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"""
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Returns true if this field's SRID corresponds with a coordinate
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system that uses non-projected units (e.g., latitude/longitude).
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"""
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return self.units_name(connection).lower() in self.geodetic_units
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def get_distance(self, value, lookup_type, connection):
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"""
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Returns a distance number in units of the field. For example, if
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`D(km=1)` was passed in and the units of the field were in meters,
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then 1000 would be returned.
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"""
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return connection.ops.get_distance(self, value, lookup_type)
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def get_prep_value(self, value):
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"""
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Spatial lookup values are either a parameter that is (or may be
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converted to) a geometry, or a sequence of lookup values that
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begins with a geometry. This routine will setup the geometry
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value properly, and preserve any other lookup parameters before
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returning to the caller.
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"""
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value = super(GeometryField, self).get_prep_value(value)
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if isinstance(value, SQLEvaluator):
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return value
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elif isinstance(value, (tuple, list)):
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geom = value[0]
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seq_value = True
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else:
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geom = value
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seq_value = False
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# When the input is not a GEOS geometry, attempt to construct one
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# from the given string input.
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if isinstance(geom, Geometry):
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pass
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elif isinstance(geom, (bytes, six.string_types)) or hasattr(geom, '__geo_interface__'):
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try:
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geom = Geometry(geom)
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except GeometryException:
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raise ValueError('Could not create geometry from lookup value.')
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else:
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raise ValueError('Cannot use object with type %s for a geometry lookup parameter.' % type(geom).__name__)
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# Assigning the SRID value.
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geom.srid = self.get_srid(geom)
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if seq_value:
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lookup_val = [geom]
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lookup_val.extend(value[1:])
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return tuple(lookup_val)
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else:
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return geom
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def get_srid(self, geom):
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"""
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Returns the default SRID for the given geometry, taking into account
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the SRID set for the field. For example, if the input geometry
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has no SRID, then that of the field will be returned.
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"""
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gsrid = geom.srid # SRID of given geometry.
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if gsrid is None or self.srid == -1 or (gsrid == -1 and self.srid != -1):
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return self.srid
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else:
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return gsrid
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### Routines overloaded from Field ###
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def contribute_to_class(self, cls, name):
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super(GeometryField, self).contribute_to_class(cls, name)
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# Setup for lazy-instantiated Geometry object.
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setattr(cls, self.attname, GeometryProxy(Geometry, self))
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def db_type(self, connection):
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return connection.ops.geo_db_type(self)
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def formfield(self, **kwargs):
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defaults = {'form_class': self.form_class,
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'geom_type': self.geom_type,
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'srid': self.srid,
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}
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defaults.update(kwargs)
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if (self.dim > 2 and 'widget' not in kwargs and
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not getattr(defaults['form_class'].widget, 'supports_3d', False)):
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defaults['widget'] = forms.Textarea
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return super(GeometryField, self).formfield(**defaults)
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def get_db_prep_lookup(self, lookup_type, value, connection, prepared=False):
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"""
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Prepare for the database lookup, and return any spatial parameters
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necessary for the query. This includes wrapping any geometry
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parameters with a backend-specific adapter and formatting any distance
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parameters into the correct units for the coordinate system of the
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field.
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"""
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if lookup_type in connection.ops.gis_terms:
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# special case for isnull lookup
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if lookup_type == 'isnull':
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return []
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# Populating the parameters list, and wrapping the Geometry
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# with the Adapter of the spatial backend.
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if isinstance(value, (tuple, list)):
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params = [connection.ops.Adapter(value[0])]
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if lookup_type in connection.ops.distance_functions:
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# Getting the distance parameter in the units of the field.
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params += self.get_distance(value[1:], lookup_type, connection)
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elif lookup_type in connection.ops.truncate_params:
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# Lookup is one where SQL parameters aren't needed from the
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# given lookup value.
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pass
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else:
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params += value[1:]
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elif isinstance(value, SQLEvaluator):
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params = []
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else:
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params = [connection.ops.Adapter(value)]
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return params
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else:
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raise ValueError('%s is not a valid spatial lookup for %s.' %
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(lookup_type, self.__class__.__name__))
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def get_prep_lookup(self, lookup_type, value):
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if lookup_type == 'isnull':
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return bool(value)
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else:
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return self.get_prep_value(value)
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def get_db_prep_save(self, value, connection):
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"Prepares the value for saving in the database."
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if value is None:
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return None
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else:
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return connection.ops.Adapter(self.get_prep_value(value))
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def get_placeholder(self, value, connection):
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"""
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Returns the placeholder for the geometry column for the
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given value.
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"""
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return connection.ops.get_geom_placeholder(self, value)
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for lookup_name in GIS_LOOKUPS:
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lookup = type(lookup_name, (GISLookup,), {'lookup_name': lookup_name})
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GeometryField.register_lookup(lookup)
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# The OpenGIS Geometry Type Fields
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class PointField(GeometryField):
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geom_type = 'POINT'
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form_class = forms.PointField
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description = _("Point")
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class LineStringField(GeometryField):
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geom_type = 'LINESTRING'
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form_class = forms.LineStringField
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description = _("Line string")
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class PolygonField(GeometryField):
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geom_type = 'POLYGON'
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form_class = forms.PolygonField
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description = _("Polygon")
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class MultiPointField(GeometryField):
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geom_type = 'MULTIPOINT'
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form_class = forms.MultiPointField
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description = _("Multi-point")
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class MultiLineStringField(GeometryField):
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geom_type = 'MULTILINESTRING'
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form_class = forms.MultiLineStringField
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description = _("Multi-line string")
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class MultiPolygonField(GeometryField):
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geom_type = 'MULTIPOLYGON'
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form_class = forms.MultiPolygonField
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description = _("Multi polygon")
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class GeometryCollectionField(GeometryField):
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geom_type = 'GEOMETRYCOLLECTION'
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form_class = forms.GeometryCollectionField
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description = _("Geometry collection")
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