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"""
This object provides quoting for GEOS geometries into PostgreSQL/PostGIS.
"""
from psycopg2 import Binary
from psycopg2.extensions import ISQLQuote
from django.contrib.gis.db.backends.postgis.pgraster import to_pgraster
from django.contrib.gis.geos import GEOSGeometry
class PostGISAdapter:
def __init__(self, obj, geography=False):
"""
Initialize on the spatial object.
"""
self.is_geometry = isinstance(obj, (GEOSGeometry, PostGISAdapter))
# Getting the WKB (in string form, to allow easy pickling of
# the adaptor) and the SRID from the geometry or raster.
if self.is_geometry:
self.ewkb = bytes(obj.ewkb)
self._adapter = Binary(self.ewkb)
else:
self.ewkb = to_pgraster(obj)
self.srid = obj.srid
self.geography = geography
def __conform__(self, proto):
"""Does the given protocol conform to what Psycopg2 expects?"""
if proto == ISQLQuote:
return self
else:
raise Exception('Error implementing psycopg2 protocol. Is psycopg2 installed?')
def __eq__(self, other):
return isinstance(other, PostGISAdapter) and self.ewkb == other.ewkb
def __hash__(self):
return hash(self.ewkb)
def __str__(self):
return self.getquoted()
def prepare(self, conn):
"""
This method allows escaping the binary in the style required by the
server's `standard_conforming_string` setting.
"""
if self.is_geometry:
self._adapter.prepare(conn)
def getquoted(self):
"""
Return a properly quoted string for use in PostgreSQL/PostGIS.
"""
if self.is_geometry:
# Psycopg will figure out whether to use E'\\000' or '\000'.
return '%s(%s)' % (
'ST_GeogFromWKB' if self.geography else 'ST_GeomFromEWKB',
self._adapter.getquoted().decode()
)
else:
# For rasters, add explicit type cast to WKB string.
return "'%s'::raster" % self.ewkb
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