97 lines
3.8 KiB
Python
97 lines
3.8 KiB
Python
class BaseSpatialOperations:
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# Quick booleans for the type of this spatial backend, and
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# an attribute for the spatial database version tuple (if applicable)
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postgis = False
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spatialite = False
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mysql = False
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oracle = False
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spatial_version = None
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# How the geometry column should be selected.
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select = None
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# Does the spatial database have a geometry or geography type?
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geography = False
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geometry = False
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# Aggregates
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disallowed_aggregates = ()
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geom_func_prefix = ''
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# Mapping between Django function names and backend names, when names do not
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# match; used in spatial_function_name().
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function_names = {}
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# Blacklist/set of known unsupported functions of the backend
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unsupported_functions = {
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'Area', 'AsGeoJSON', 'AsGML', 'AsKML', 'AsSVG',
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'BoundingCircle', 'Centroid', 'Difference', 'Distance', 'Envelope',
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'ForceRHR', 'GeoHash', 'Intersection', 'IsValid', 'Length', 'MakeValid',
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'MemSize', 'NumGeometries', 'NumPoints', 'Perimeter', 'PointOnSurface',
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'Reverse', 'Scale', 'SnapToGrid', 'SymDifference', 'Transform',
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'Translate', 'Union',
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}
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# Constructors
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from_text = False
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from_wkb = False
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# Default conversion functions for aggregates; will be overridden if implemented
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# for the spatial backend.
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def convert_extent(self, box, srid):
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raise NotImplementedError('Aggregate extent not implemented for this spatial backend.')
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def convert_extent3d(self, box, srid):
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raise NotImplementedError('Aggregate 3D extent not implemented for this spatial backend.')
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# For quoting column values, rather than columns.
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def geo_quote_name(self, name):
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return "'%s'" % name
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# GeometryField operations
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def geo_db_type(self, f):
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"""
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Return the database column type for the geometry field on
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the spatial backend.
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"""
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raise NotImplementedError('subclasses of BaseSpatialOperations must provide a geo_db_type() method')
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def get_distance(self, f, value, lookup_type):
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"""
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Return the distance parameters for the given geometry field,
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lookup value, and lookup type.
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"""
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raise NotImplementedError('Distance operations not available on this spatial backend.')
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def get_geom_placeholder(self, f, value, compiler):
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"""
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Return the placeholder for the given geometry field with the given
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value. Depending on the spatial backend, the placeholder may contain a
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stored procedure call to the transformation function of the spatial
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backend.
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"""
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raise NotImplementedError('subclasses of BaseSpatialOperations must provide a geo_db_placeholder() method')
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def check_expression_support(self, expression):
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if isinstance(expression, self.disallowed_aggregates):
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raise NotImplementedError(
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"%s spatial aggregation is not supported by this database backend." % expression.name
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)
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super().check_expression_support(expression)
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def spatial_aggregate_name(self, agg_name):
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raise NotImplementedError('Aggregate support not implemented for this spatial backend.')
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def spatial_function_name(self, func_name):
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if func_name in self.unsupported_functions:
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raise NotImplementedError("This backend doesn't support the %s function." % func_name)
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return self.function_names.get(func_name, self.geom_func_prefix + func_name)
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# Routines for getting the OGC-compliant models.
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def geometry_columns(self):
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raise NotImplementedError('Subclasses of BaseSpatialOperations must provide a geometry_columns() method.')
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def spatial_ref_sys(self):
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raise NotImplementedError('subclasses of BaseSpatialOperations must a provide spatial_ref_sys() method')
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