68 lines
2.2 KiB
Python
68 lines
2.2 KiB
Python
"""
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This object provides quoting for GEOS geometries into PostgreSQL/PostGIS.
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"""
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from psycopg2 import Binary
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from psycopg2.extensions import ISQLQuote
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from django.contrib.gis.db.backends.postgis.pgraster import to_pgraster
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from django.contrib.gis.geometry.backend import Geometry
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class PostGISAdapter:
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def __init__(self, obj, geography=False):
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"""
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Initialize on the spatial object.
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"""
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self.is_geometry = isinstance(obj, (Geometry, PostGISAdapter))
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# Getting the WKB (in string form, to allow easy pickling of
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# the adaptor) and the SRID from the geometry or raster.
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if self.is_geometry:
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self.ewkb = bytes(obj.ewkb)
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self._adapter = Binary(self.ewkb)
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else:
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self.ewkb = to_pgraster(obj)
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self.srid = obj.srid
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self.geography = geography
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def __conform__(self, proto):
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"""Does the given protocol conform to what Psycopg2 expects?"""
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if proto == ISQLQuote:
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return self
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else:
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raise Exception('Error implementing psycopg2 protocol. Is psycopg2 installed?')
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def __eq__(self, other):
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if not isinstance(other, PostGISAdapter):
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return False
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return (self.ewkb == other.ewkb) and (self.srid == other.srid)
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def __hash__(self):
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return hash((self.ewkb, self.srid))
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def __str__(self):
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return self.getquoted()
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def prepare(self, conn):
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"""
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This method allows escaping the binary in the style required by the
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server's `standard_conforming_string` setting.
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"""
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if self.is_geometry:
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self._adapter.prepare(conn)
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def getquoted(self):
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"""
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Return a properly quoted string for use in PostgreSQL/PostGIS.
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"""
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if self.is_geometry:
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# Psycopg will figure out whether to use E'\\000' or '\000'.
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return '%s(%s)' % (
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'ST_GeogFromWKB' if self.geography else 'ST_GeomFromEWKB',
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self._adapter.getquoted().decode()
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)
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else:
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# For rasters, add explicit type cast to WKB string.
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return "'%s'::raster" % self.ewkb
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